Science
Term-I
Class-IX B.S. Tomar M.Sc., Ph.D.
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Publications Pvt. Ltd.
Syllabus Class - IX Course Structure First Term
Marks: 90
Units
Marks
I. Food
13
II. Matter - Its nature and behaviour
29
III. Organisation in the living world
18
IV. Motion, force and work
30
Total
Theme: Food
90
(10 Periods)
Unit: Food Plant and animal breeding and selection for quality improvement and management; use of fertilizers, manures;- protection from pests and diseases; organic farming.
Theme: Materials
(22 Periods)
Unit: Matter - 'Nature and behaviour Definition of matter; solid, liquid and gas; characteristics - shape, volume, density; change of state-melting (absorption of heat), freezing, evaporation (Cooling by evaporation), condensation, sublimation.
Nature of matter: Elements, compounds and mixtures. Heterogeneous and homogenous mixtures, colloids and suspensions.
Theme: The World of The Living
(22 Periods)
Unit: Organization in the living world Cell- Basic Unit of life: Cell as a basic unit of life; prokaryotic and eukaryotic cells, multicellular organisms; cell membrane and cell wall, cell organelles; chloroplast, mitochondria, vacuoles, endoplasmic reticulum, golgi apparatus; nucleus, chromosomes - basic structure, number. Tissues, Organs, Organ System, Organism. Structure and functions of animal and plant tissues (four types in animals; meristematic and permanent tissues in plants).
Theme: Moving Things, People and Ideas
(36 Periods)
Unit: Motion, force and work Motion: Distance and displacement, velocity; uniform and non-uniform motion along a straight line; acceleration, distance-time and velocity-time graphs for uniform motion and uniformly accelerated motion, equations of motion by graphical method; elementary idea of uniform circular motion. Force and Newton's laws: Force and motion, Newton's laws of motion, inertia of a body, inertia and mass, momentum, force and acceleration. Elementary idea of conservation of momentum, action and reaction forces.
Gravitation: Gravitation; universal law of gravitation, force of gravitation of the earth (gravity), acceleration due to gravity; mass and weight; free fall.
Continuous and Comprehensive Evaluation Formative Assessment •
Formative assessment is atool used by the teacher to continuously monitor student progress in anon-threatening supportive environment.
•
It involves regular descriptive feedback, achance for the student to reflect on the performance, take advice and improve upon it.
•
It involves students being an essential part of assessment from designing criteria to assessing self or peers.
•
If used effectively, it can improve performance tremendously while raising the self esteem of the child and reducing the workload of the teacher.
Summative Assessment • • •
Summative assessment is carried out at the end of a course of learning. It measures or 'sums-up' how much a student has learned from the course. It is usually a graded test, Le., it is marked according to a scale or set of grades.
Grading System Scholastic A
Scholastic B Grade Point
Grade
Exceptional
10.0
A+
A2
Excellent
9.0
A
71-80
B1
Very Good
8.0
B+
61-70
B2
Good
7.0
B
51-60
C1
Fair
6.0
C
41-50
C2
Average
5.0
33-40
0
Below Average
4.0
21-32
E1
Need to Improve
00-20
E2
Unsatisfactory
Marks Range
Grade
91-100
A1
81-90
Attributes
Promo1j'on is based on the day-to-day work of the students throughout the year and also on the performance in the terminal exami a ·on.
*Firs e ~SeGofld
term
-FA1 (10%) + FA2 (10%) + SA1 (30%)
Formative Assessment (FA) 1+2+3+4
=40%
-FA3 (10%) + FA4 (10910) + SA2 (30%)
Summative Assessment (SA) 1+2
=60%
The system being implemented will have the following advantages: •
It will minimise misclassification of students on the basis of marks.
•
It will eliminate unhealthy cut-throat competition among high achievers.
•
It will reduce societal pressure and will provide the learner with more flexibility. I
will lead to afocus towards a better learning environment.
Chapter: One
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(UJ mJ ~~ ©~ ~J~~ Introduction There are over 1.7 million kinds of organisms. They all show an enormous degree of diversity of form and size. Yet they have an underlying unity in their basic structure and process. All living structures we see around us are essentially made up of numerous compartments (microscopic units) called cell. Robert Hooke (1665) is credited with the discovery of cell. When Hooke made his chance observation through a -self-designed microscope, he observed a honeycomb-like pattern in a very thin slice of cork (Fig. 1.2). This honeycomb-like structure consisted of a thick wall enclosing box-like compartments. Hooke called these boxes, cells. Actually, cell is a Latin word for 'a small room'. This may seem an insignificant incident, but it held a lot of importance in the history of science. This was the very first time that someone had observed that living things appear to consist of such separate units. The use of the word 'cell' to describe the unit is prevalent till this day in biology.
Fig.11 Robert Hooke's rricroscope
Let us perform an activity to find out cells.
8ctivig1 • Take a small piece from an onion. • Use a forcep to separate a peel from its inner layers (concave side). • Put this inner layer immediately in a watch-glass containing water. This will prevent the peel from getting folded or dry.
Q
~Q 1='9 • _3 Prep,
Fig. 1.2 Slice of cork showing cells
P
O__Q
__ ~ng
,,,rporaf'/ mou, I a onion
lee,
• Now, take a glass slide, put a drop of clean water on it and transfer the small piece of onion peel from the watch-glass on to the slide. Make sure that the peel is perfectly flat on the slide. • For this, you may need a thin camel hair paintbrush. • Put a drop of iodine solution on the piece of onion peel. • Gently place the cover-slip onto the slide using a mounted needle to avoid air bubbles. • This is how you prepare a temporary mount of onion peel. For observation place the slide onto the stage of the microscope. • Carefully observe the slide under microscope using the low power and high power of a compound microscope. The Fundamental Unit of Life
5
MICROSCOPE
Eyepiece --.;#'f!/:""t
: ; : . - - - - Tube Coarse adjustment Fine - - - " ' I ' adjustment
Objective lens _ _ _ (high power) 7...~---
Objective lens (low power)
Clip---
Stage height -----.;~ adjustment
Cells are very small in size and cannot be seen by the naked eye. For observing a minute cell one needs a microscope. Leeuwenhoek prepared. a light microscope which is comparable to today's compound microscope. The object (specimen) on a glass slide is kept on a stage, bearing a central hole under an objective lens. Light is reflected through the specimen with the help of a mirror and a condenser from below the stage. Through the eye piece one can see the magnified image of an object. Eye piece is located at the top. Focussing is usually done by the adjustors (coarse and fine) fitted in the microscope. Eye piece and objectives of high and low powers are available.
Fig. 1.4 Compound microscope and its parts
Cell wall I::!::=i!-- Cytopl asm
Nucleus Vacuole
Fig. 1.5 Cellular structures of onion peel
What do you observe when you look through the lens? Can you draw the structures that you are able to see through the microscope in your observation sheet? Does it look like the Fig. 1.5. When you try preparing temporary mounts of peel of onions of different sizes, you will find that all contain similar small struc;tures. These small structures which you see in an onion peel are the basic building units.called cells. ot only onions, but all organisms which you see around are made up of cells.
Discovery of Cell The term 'cell' was used by Robert Hooke in 1665. He observed cells in a piece of cork under a primitive microscope. In 1674, Anton von Leeuwenhoek discovered free cells like bacteria, protozoa, red blood cells and sperm with the help of improved microscope. Robert Brown in 1831 discovered the nucleus in the cells. In 1839, Johannes Purkinje named the fluid content of the cell as protoplasm. In 1892, O. Hertwig proposed that cell is a mass of 'protoplasm' . • Cell is the structuml and functional unit of life.
• A cell arises from a pre-existing cell.
6
Cell Theory . All plants and animals are composed of cells and that the cell is the basic unit of life, ,vas presented by two biologists-Matthias Jacob Schleiden (German Botanist) and T. Schwann (German Zoologist), in 1839. In 1855, R. Virchow further expanded the cell theory as, "Omnis cellulae a cellula", i.e., all cells arise from pre-existing cells. Soon thereafter in 1866, Haeckel, established that nucleus stores and transmits hereditary traits. In 1880, Fleming had shown that cells ensure continuity between one generation and another by The Fundamental Unit of Life
the mechanism of mitosis. Waldeyer in 1890 described the precise division of the chromosomes. Thus, the modern version ofthe cell theory is as follows: (i) All living organisms are composed of cells and their products. (ii) Cell is the structural and functional unit of life. (iii) All cells arise from pre-existing cells. (iv) The smallest unit of life is the cell, i.e., every organism starts its life as a single cell. With the discovery of electron microscope in 1940, it was possible to observe and understand the complex structure of the cell and its various organelles. The first electron microscope was designed by Knoll and Ruska in 1932.
Fig. 1.6 Electron microscope
Unicellular and Multicellular Organisms We cannot imagine an organism that is not formed of a cell. Organisms may be made up of one or more cells. If the organisms are made up ofa single cell, they are called unicellular organisms (uni-single), e.g., Amoeba, Chlamydomonas, Paramecium and bacteria. On the other hand, if organisms are made up of many cells, they are called multicellular organisms (multi-many). The multicellular organisms may be made up of few cells (e.g., some algal and fungal forms) to several million cells (e.g., human being, tree, whale, etc.). In a multicellular organism certain cells become specialised to perform a specific function and thus division of labour is established among different groups of cells. The group of cells having a common origin and performing a similar but specific function constitute a tissue (e.g., muscles). Several different types of tissues may join collectively to form an organ which carries out one or more specific functions (e.g., kidney, liver, brain). Several organs are inter-related to perform a specific function and thus, constitute an organ system (e.g., digestive system, circulatory system, nervous system, etc.). The life of every multicellular organism begins as a single cell. However, the unicellular organisms, complete their entire life cycle as a single cell. In others, .an increase in the number of cells takes place in the course of life. All the cells of our body come from a single cell, zygote, which divides continuously to form our multicellular body. Thus, all cells come from pre-existing cells. The cells are not only the building blocks of our body, they are functional units of life too. Each living cell has the capacity to perform certain basic functions that are performed by all living forms. If you study Fig. 1.10, you will observe that human beings have different types of cells like sperm, blood cell, bone cell, muscles cell, nerve cell, fat cell, etc. We know that there is division of labour in multicellular organisms, e.g., human beings. It means that different parts of the human body perform different functions. The human body has a heart to pump blood, a stomach .. to digest food and so on. Likewise, in a human body, the division of labour is also seen inside a single cell. In fact, each cell has got certain specific components inside the cell, called cell organelles. Each type of cell organelle performs a special function, e.g., protein synthesis, food synthesis, clearing up the waste material from the cell, etc. Thus, all the activities of an organism are present in miniature forms in each and every cell. So, a cell is able to live and perform its function due to these organelles. These organelles together constitute the basic unit called the cell. Therefore, the cell can be called a basic unit of life and the structural unit of an organism The Fundamental Unit of Life
7
--------------------------t.~~~~--,.-.
Cell is made of a living substance called protoplasm. (proto = first, plasma = liquid). The protoplasm is made up of four elements namely carbon, hydrogen,
nitrogen and oxygen. Other elements such as phosphorous, sulphur and calcium are also present. These elements combine to form compounds like water, proteins, fats, carbohydrates and nucleic acid (DNA and RNA), etc. activi~2 • • • • • •
Try preparing temporary mounts of leaf peels, onion root zip. lOu can also take leaf of maize, mustard or tmdescantia for this purpose. Take a red-coloured tmdescantia leaf Take out a small peel fTOm the lower surface of the leaf with a quick jerk. Prepare temporary mount of this peel. Place it under the microscope and observe it. lOu will observe that each cell is filled with red-coloured cell sap.
activi~3 • Keep a drop of your blood on a glass slide with the help of a sterile needle. • Smear the blood over- the centre of a slide with the help of another slide. • Put a drop of methylene blue stain on top of the smear and cover the slide with a coverslip. • When dry, observe the slide first under low power and then under high power microscope. • Identify and draw its structure.
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Platelets
~_
.
~._
.ft
Red blood corpuscles ~
g.
~ ~
Ce
5 .~ huma~ blood
You will observe the blood cells in the slide as shown in Fig. 1.7. After performing the above activity you will be able to give answer to the following questions. (i) Do all cells look alike in terms of their shape and size?
(ii) Could you find differences among cells from different parts of a plant body. (iii) \'\That similarity could you find? Answers: (i) All cells of a multicellular organism are of different shapes and sizes and cells of different organisms are different. (ii) The different parts of a plant body are different in shape, size and structure. (iii) The similarities among all the cells of higher organisms are that they contain plasma membrane, a cytoplasm which contains cell organelles and a nucleus.
Prokaryotic and Eukaryotic Cells
I
(a) Prokaryotic cell
Organisms with cells in which the nuclear material is not bounded by a definite nuclear membrane are called prokaryotes, e.g., bacteria and blue-green algae. 8
The Fundamental Unit of Life
These are the most primitive cells. Nuclear material consists of a single chromosome which is in direct contact with the cytoplasm. In a prokaryotic cell, other membranebounded organelles, such as mitochondria, endoplasmic reticulum, lysosome, chloroplast, golgi bodies, etc., are also absent. However, ribosomes are present in such cells. ..-----. ~
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--\~ ~
Protein coat~
DNA~(\~:'J",
or RNA
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DNA
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Cytoplasm
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Cytoplasm
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Plasma membrane
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Nuclear membrane
Nodoo'", Nucleoplasm
(c)
(b)
Fig. 1.8 (a) Virus. (b) Prokaryotic ceil of bacteria. (el Eukaryotic cell of animal
I
(b) Eukaryotic cell
These are advanced and complete cells in which the nucleus has a definite nuclear membrane. In eukaryotic cells, other membrane-bounded organelles, such as mitochondria, ribosome, lisosome, E.R., chloroplast, golgi body are present. Viruses do not easily fit in the definition of a cell and they are often described as 'living chemicals' or as cellular forms which are degenerated through parasitism. Virus is an infectious, sub-cellular and ultramicroscopic particle which divides only in the host cell and can be transmitted by injection and causes characteristic reactions in the host cell. Viruses lack internal organisation which is the characteristic of a cell. The viruses living within the bacteria are called bacteriophages. The cells of bacteria are different from animal and plant cells. Bacterial cells are prokaryotic cells, whereas plant and animal cells are eukaryotic. The important differences between prokaryotic cells and eukaryotic cells have been given in Table 1.1. Table 1.1 Differences between Prokaryotic and Eukaryotic cells S.No.
Feature
Prokaryotic cells
I
Eukaryotic cells
1.
Size
Generally small, 1- 10 !-Lm
Generally large, 5-100 !-LID
2.
Cell
Non-cellulosic
Cellulosic in plants only
3.
Cell organelles
Absent except ribosomes
Present, e.g., mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, plastids, etc.
4.
Nuclear membrane
Absent. Nucleoid or nuclear Present. DNA is surrounded region is not surrounded by by a nuclear membrane nuclear membrane, i.e., DNA is n
5.
Chromosome
Single
More than one
6.
Nucleolus
Absent
Present
7.
Cytoskeleton
Absent
Present
8.
Cell division
By fission or budding (amitosis) Mitotic or meiotic
The Fundamental Unit of Life
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FORMATIVE ASSESSMENT FA 1.1 Multiple Choice Questions Select the right choice: 1. The basic structural and functional unit of all living organisms is alan (a) organ (b) tissue (c) cell (d) proteins 2. The cell was discovered by (a) Robert Brown (b) Leeuwenhoek (c) Robert Hooke (d) Flemming 3. An undefined nuclear region containing only nucleic acid in prokaryotes is known as (a) nucleus (b) nucleolus (c) cellulose (d) none of these 4. The organism lacking nucleus and membrane-bound organelles are (a) prokaryotes (b) dipleids (c) eukaryotes (d) none of these 5. The only cell organelle present in prokaryotic cell is (a) mitochondria (b) ribosome (c) plastids (d) lysosome
FA 1.2 Match the Following Match the terms given in column I to their meanings in column II. Column I
Column II
(a) First electron microscope
(i) Only ribosomes present
(b) Nucleus
(ii) Knoll and Ruska
(c) Prokaryotes
(iii) Robert Brown
(d) Cell theory
(iv) An undefined nuclear region in prokaryotes
containing only nucleic acid (e) Nucleoid
(v) Schleiden and Schwann
FA 1.3 Complete the Table Complete the following table by writing appropriate answer. Feature
Cell wall
Prokaryotic cell
Non-cellulosic Present, e.g., mitochondria, endoplasmic, reticulum, Golgi apparatus, lysosomes, plastids, etc.
Cell organelle
Nucleolus Cell division
10
Eukaryotic cell
Absent Mitotic or meiotic
The Fundamental Unit of Life
FA 1.4 If I
SA •••••
?"' orksheet
Pretend yourself to be an eukaryotic cell and answer the following questions accordingly. 1. 2. 3. 4.
Write your defining features with examples. Differentiate between prokaryotic and your cell. What is the difference between your nucleus and prokaryotic cell's nucleoid. Write down the name of your cell organelles..
FA 1.5 Activity-based ~'Vorksheet Observe permanent slide of onion root tip or peels of onions of different sizes. After carefully observing the permanent slides answer the following questions. 1. 2. 3. 4.
Do all cells look alike in terms of shape and size? Do all cells look alike in structure? Could we find differences among cells from different parts of a plant body? What similarities could we find?
Cell Definition of cell: According to Loewy and Siekevitz.(1963), cell is a unit of biological activity surrounded by a selectively permeable membrane and capable of self reproduction.
I
Cell shape
The shape of the cells are related to their functions. It may be variable or fixed. Cell shape is variable like Amoeba and leucocytes (white blood cells). Amoeba (single-celled animal) during locomotion changes its shape; similarly leucocytes also change their shape by producing pseudopodia and become irregular in shape. Water globules
Contractile vacuole
0'/1
Crystals
Nucleus
"
Plasmalemma
~
" \ ----- Endoplasm
o Food vacuole
::
Hyaline cap
Fig. 1.9 Amoeba
In most cases the shape of a cell is fixed, e.g., plants and animals (including Paramecium, Euglena, etc). In case of unicellular organisms, the cell shape is maintained The Fundamental Unit of Life
11
by a tough cell membrane (e.g., Paramecium) and exoskeleton (e.g., Elphidium, Polystomella). In case ofmulticellular organisms, the shape ofthe cells depends on their functional adaptations and partly on surface tension and viscosity of the protoplasm, mechanical action exerted by adjacent cells and turgidity of the cell membrane. Therefore, cells may have diverse shapes, such as spherical (eggs cells), elongated (nerve cells), branched (pigment cells of skin), discoidal (RBC) and so on. (see Fig. 1.10).
Cells lining intestinal tract
Blood cells
Fat cell
Neuron in brain
-~~ Ovum
Sperm
~ •
Fig. 1.10 Examples of various types of cells
I
Fig. 1.11 Acetabularia
Cell size
The size of the cells varies greatly in plants and animals. Some cells are visible to the naked eye like egg of ostrich (18 em) and ovule of Cycas. Some nerve cells of human beings have a metre long 'tail'- axon. A single-celled algae AcetabulaTia is 10 ,urn in height (see Fig. 1.11) and sclerenchyma cells (fibre cells) of Manila hemp are more than 100 em in length. Most prokaryotic cells are in the range of 1 to 10,um (one micrometre is one thousandth ofa millimetre). Most eukaryotic cells are microscopic measuring 10-100 mm. The size of a unicellular organism is larger than a typical cell of multicellular organism, e.g., Amoeba pTOteus is the biggest among all unicellular organisms. Its length is 60 ,urn (0.6 mm). In multicellular organism, the size of cells ranges from 20-30 ,urn. The smallest cells are found in bacteria (0.2,um0.1 ,urn), e.g., Mycoplasma gallisepticum, that is an organism intermediate between the virus or bacteria. Its size is about 0.1 ,urn.
I
Cell volume
The cell volume, in general, is fairly constant for a particular cell type and is independent of the size of the organism. For example, kidney and liver cells are about the same size in the mouse, horse and bull. The difference in size of organisms depends on number of cells only and not on the volume of the cells. Therefore, the cells of an elephant are not larger than those of other tiny animals or plants. Due to the large number of cells present in the body, the elephant becomes large.
12
The Fundamental Unit of Life
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I
Cell number
The cell number in an organism varies with the size of organism. Unicellular organisms have a single cell. In multicellular organisms, the cells are indefinite. In Pandorina, number of cells are 8, 16,32 or 64 and in Eudorina 16,32 or 64. In man, the number of cells is about 100 trillion (l0 14 ).
Structure of a Cell If you observe a cell under the microscope, you will come across three features in almost every cell- plasma membrane, nucleus and cytoplasm. Each cell has an outer boundary called plasma membrane. Inside the plasma membrane lies the cytoplasm. Various cell organelles are suspended in the cytoplasm. All activities inside the cell and interaction of the cell with its environment are possible due to these features. In addition to these organelles, nucleus is also seen under the microscope. Pinocytic vesicle
Mitochondrion
NUCleus
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Smooth endoplasmic reticulum
Centrioles
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Rough . endoplasmic reticulum
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Pinocytic vesicle forming
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6~U¥.
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membrane Golgi body
Microtubules
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Lysosome
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Ribosomes
C'9 1.i3 Plant ce
The Fundamental Unit of Life
13
I
(A) Plasma membrane or cell membrane
Being a discrete 'unit of life' every cell is bounded by an extremely delicate membrane which separates the cell from its non-living surrounding (extracellular medium) and thus, provides a separate identity to the cell. This membrane is called plasma membrane (cell membrane or plasmalemma). Structure
Plasma membrane is a living, thin, delicate, elastic, selectively permeable membrane. It is about 7 nm (70 A) thick. We can observe it only through an electron microscope. Chemical analysis has shown that the membrane contains seventy five per cent phospholipids. In addition, the membrane contains proteins, cholesterol and polysaccharides. In 1972, Jonathan Singer and Garth Nicholson suggested a model, called fluid mosaic model for explaining the ultra structure of plasma membrane. According to them, membrane is a lipid bilayer having integrated protein molecules. The membrane is semifluid and dynamic in nature. The lipid and protein help in performing transport movements. Two types of protein distinguished are: (i) Intrinsic proteins or Integral proteins (ii) Extrinsic proteins or Peripheral proteins
Intrinsic proteins: These are completely span on the lipid bilayers. Extrinsic proteins: These are either on the outer surface or on the inner surface of the lipid membrane. This model of membrane has been described as 'a number of protein icebergs floating in the sea oflipids'. This model was the most acceptable one. Branching carbohydrate portion of protein which acts as an antigen
I
Hydrophobic tails 0 phospholipid molecules
Intrinsic protein molecule spanning the phospholipid layer
Pore
Extrinsic protein molecule lying on the surface
Fig. 1.14 Fluid mosaic model of plasma membrane
Functions
The plasma membrane permits the entry and exit of some materials in the cell. It also prevents movement of some other materials. Therefore, the cell membrane
is called selectively permeable membrane. Now, let us find out how the movement of substances takes place across the cell. How do substances move in and out of the cell? Some substances such as carbon dixoide (C0 2 ) and Oxygen (02) can move across the cell membrane by the process of diffusion. These substances are of • I I~
14
The Fundamental Unit of Life
very small size, therefore, diffuse readily through the phospholipid layer of cell membrane. To understand this process better, let us perform an activity.
activity 4
r::::::~=~'n
• Take a glass halffilled with clean water. • Put a few drops of any coloured fluid in it. Observe it carefully. • What do you see? Does the water of the glass get uniformly coloured at once?
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Fig. 1.15 Cells
You will observe that the water takes the colour uniformly throughout the beaker. This is due to a process called diffusion. This is spontaneous movement of a substance from a region of high concentration to a region where its concentration is low.
Diffusion Diffusion is the movement of molecules of any substance from a region ofhigher concentration to lower concentration. This is because of the natural tendency of a substance to spread uniformly in the dispersion medium by random movement of its molecules and ions. Diffusion is faster in the gaseous phase than in liquids and solids. Something similar happens in the cells too, for example, when a gas like carbon dioxide (that is the waste product of respiration) gets accumulated in high concentration inside the cell. In the cell's external environment, the concentration of CO 2 is low as compared to that inside the cell. As soon as there is a difference of concentration of CO 2 between inside and outside of a cell, CO 2 moves out of the cell, i.e., from a region of high concentration to a region of low concentration through the process of diffusion. In the same way, 02 enters the cell by the process of diffusion when the concentration of 02 inside the cell decreases. Thus, diffusion plays an important role in exchange of gases between the cells and its external environment. Similarly, water molecules also diffuse through the plasma membrane and this is called osmosis.
Diffusion into cell (more 02 in water)
Amoeba _ J., /""-..., cell,>< / ~ / / '' - . ~ \. (less O2 in cell) 02 " ' , \ used up in \ (' respiration l"-,\ ,,\ore C02 in
r----/
C:lI
.
\ "'----0
\...-..'1-----.J
Diffusion out of cell (less CO 2 in water
around the cell)
Fig. 1.16 Diffusion of oxygen and carbon dioxide across the plasma membrane of Amoeba
Osmosis The movement of water molecules through the selectively permeable membrane is called osmosis. The movement of water across the plasma membrane is also affected by the amount of substance dissolved in water. Thus, osmosis is the passage of water from a region of high water concentration through a semipermeable membrane to a region of low water concentration. Therefore, osmosis can be defined as the diffusion of water or solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. Let us see what will happen to an animal cell or a plant cell when placed in a solution of sugar or salt. One of the following three things could happen: 1. When the medium surrounding the cell has a higher water concentration than the cell, meaning that th~ outside solution is very dilute, the cell will gain water by osmosis. Such a solution is known as a hypotonic solution In such a solution, water molecules are free to pass across the plasma membrane in both the directions, but more water molecules come into the cell than they leave. The net (overall) result is that water enters the cell. The cell is likely to swell up.
The Fundamental Unit of Life
15 ."
----------------------
2.
When the relative concentration of water and solutes on either side of the plasma membrane are the same then there will be no net movement of water across the plasma membrane. Such a solution is known as an isotonic solution. In such a solution, water crosses the cell membrane in both directions, but the amount going in is the same as the amount going out, therefore, there is no overall movement of water. In this lpu,ewale, solution, the cell will stay the same siz€. (solvent) 3. If the medium has a less concentration of water and higher Water molecules concentration of salt than the cell, it means that it is a very I-t---+--entering into concentrated solution. The cell will lose water by osmosis. Such a funnel solution is known as a hypertonic solution. Semipermeable In such case, water crosses the cell membrane in both directions, membrane but this time more water leaves the cell than it enters. Therefore, Fig, 1.17 A simple osmometer. Water molecules (solvent) entering the the cell will shrink. Thus, osmosis is a special case of diffusion sugar solution (solute) through a selectively permeable membrane. Semipermeability of the membrane prevents sugar molecules moving into the solvent Let us tryout the following activity:
activity 5 • Take an hen's egg. • Remove the egg shell by dissolving it in dilute hydrochloric acid. The hard shell of the egg that is made of mainly calcium carbonate gets dissolved. The egg is now enclosed by a thin outer semipermeable shell membrane. • Put the egg in pure water for 5 minutes and then observe. • What do you observe? • 10u will observe that the egg swells because waterenters the egg by osmosis through cell membrane. • Put a similar deshelled egg into concentrated salt solution for 5 minutes and observe it. • What do you observe? You will observe that the egg shrinks after a few minutes. Why does the egg shrink? This is because the water passes out of the egg into the salt solution as the salt solution is more concentrated. You can also try a similar activity with dried raisins or apricots.
8ctivity& Demonstration of Osmosis in Raisins Soil particle Thin film of water Fig. 1.18 Absorption of soil waters by root hair
• Put dried raisins and apricots in pure clean water. • Leave them for some time and observe. • After some time you will observe that the raisins swell up due to endosmosis. Now, place the swollen raisins into a concentrated salt solution and observe it. You will observe that the raisins shrink as they lose water due to exosmosis. Some Examples of Osmosis
Unicellular freshwater organisms and most plant cells tend to gain water through osmosis. Absorption of water by plant roots is also an example of osmosis. Hence, diffusion is important in exchange of gases and water in the life of a cell. In addition to this, the cell also obtains nutrition from its environment. Different molecules move in and out of the cell through a type of transport requiring use of energy. 16
The Fundamental Unit of Life
Endocytosis
o :::J:::=-
Solutes
:
:
Invaginated membrane
!
Pinocytotic vesicle
~Extracellular fluid
The flexibility of the plasma membrane also enables the cell to engulf food and other materials from its external environment. Such processes are known as endocytosis. It is the active cellular intake of materials. It is of two types: (i) Phagocytosis (cell eating) (ii) Pinocytosis (cell drinking)
(i) Phagocytosis: The transport ofsolid matter like food, phathogens and foreign matter across the membrane by forming detachable vesicles is called phagocytosis or cell eating. It is a common method of feeding among the protozoans such as Amoeba and lower metazoa (e.g., sponges) for engulfing food particles.
In amoeba and other protozoans, the food particles get surrounded by an area of plasma membrane (cell surface) which forms an invagination along with the food organism. The invagination pinches off into a vesicle. Such vesicles with food particles are known as phagosomes. (ii) Pinocytosis (cell drinking): The intake of droplets of extracellular fluid along with sub-microscopic particles is called pinocytosis or cell drinking. Pinocytosis help in the intake of solutes such as insulin and lipoproteins in concentrated form. In this process extracellular fluid adheres to specific receptors of the membrane and invagination is formed. This is drawn inwards and pinched off as a membrane-bound vesicle, the pinosome, containing the solute. The pinocytic vesicle moves into the cytoplasm and its contents are assimilated. Pinocytosis is a common occurrence in the cells lining the blood capillaries. Ions, sugar and amino acids enter the cells by pinocytosis.
o
00 0
"1
A~\
;:::::Y
~~
Pseudopodium Particulate material Plasma membrane
~ ~Ph,g",om, Fig. 1.19 Diagrammatic representation of (A) The process of Pinocytosis and (B) Phagocytosis through plasma membrane
Exocytosis The process of exudating the secretory materials from the cell is called exocytosis or cell vomitting. Exocytosis occurs in various cells to remove undigested residues of substances brought in by endocytosis. In the gland cells, secretion collects in a membrane-bound vacuole which now moves to the surface. Here it fuses with the plasma membrane. In the fused membrane, a channel is formed and the contents of the vacuole are discharged outside the cell. Table 1.2 Living and Non-living Parts of Cell S.No.
Living parts
Non-living parts
1.
Plasma membrane
Cell wall (in plants)
2.
Cytoplasm (i) ER (smooth and rough) (ii) Mitochondria (iii) Colgi bodies (iv) Ribosomes (v) Lysosomes (vi) Plastids (only in plants) (vii) Centrioles (only in animals)
Vacuoles
The Fundamental Unit of Life
17
Cell Wall
Plant cells, in addition to plasma membrane, have another rigid outer covering called the cell wall which lies outside the plasma membrane. The cell wall is nonliving and freely permeable and is secreted by the cell itself for the protection of its plasma membrane. It is also present in bacteria, fungi and algae. It is absent in animal cells. Cell wall determines the shape of a plant cell and prevents desiccation of cells. The cell wall in bacteria is composed ofprotein and non-cellulosic carbohydrates, and in plants, of cellulose. Functions (i) It provides mechanical strength to the cell. (ii) It controls the size and shape of the cells. (iii) It counteracts, i.e., protects the cells against the osmotic pressure excreted by
(iv) (v)
(vi) (vii)
the cell contents. It helps in the translocation of water and other substances through xylem vessels and tracheids. It plays an important role in cell expansion. Cutin and suberin prevent loss of water by evaporation. Protects the cell from pathogens.
Plasmolysis
If plant cells are immersed in a hypertonic solution, water will diffuse out of the cell because concentration of water molecules in the cells is more than that in the outer solution. Due to continuous exosmosis, protoplasm shrinks and separates from the cell wall. This phenomenon is called plasmolysis. To better understand this phenomenon let us perform the following activity:
activity 7 • Mount the peel of a Rheo leaf and place it in a clean glass slide. • Put a drop of strong solution of sugar or' salt on the mounted leaf on the slide and cover it with a coverslip. • After few minutes observe it under the microscope. • What do you see? • 10u will observe that the cell membrane shrinks after a few minutes. (See Fig. 1.20). These changes can be explained by the fact that outer medium is hypertonic. Therefore, water moves out of the leaf cells to cause plasmolysis. Space filled with external solution
Cytoplasm
Vacuole
Tonoplast--.......,,-
Normal cell
Plasmolysis begins
Permanent plasmolysis
Fig. 1.20 Structure of a p ant cell
18
The Fundamental Unit of Life
rl:nlU
• Now take another peel of a Rheo leaf which has been placed in boiling water for a few minutes. • Prepare the slide similarly and observe it under the microscope. • Put a drop of strong solution ofsugar or salt on the slide. • Wait for a few minutes and observe it again. • What do you find? Did plasmolysis occur now? You will observe that plasmolysis does not occur. This means that the process of osmosis does not occur in boiled plant cells. Due to boiling, i.e., high temperature, the cell membranes get damaged, hence, there will not be any osmotic activity. This activity proves that the property of selective permeability exists only in the living cell membrane and they are therefore, able to absorb water by osmosis.
activity 8 Observation of Nucleus in the Animal Cells.
• • • • •
Take a clean microscope slide and put a drop of water on it. The teacher will provide you cotton bud from a freshly opened pack. Gently wipe the lining ofyour cheek with one end of the cotton bud. Smear the cotton bud over the centre of the slide. Dispose offthe cotton bud immediately into a beaker ofdisinfectant provided by your teacher.
C c;/ q
? I: =-
Fig. '.2'
• Put a drop of methylene blue stain on top of the smear. • Place a cover-slip on top and look for cells under a high powered microscope. What do you observe under the microscope? Can you draw the structure that you are able to see on your observation sheet? You will see a spherical or oval, dot-like structure near the centre of each cheek cell. These structures are called nucleus. You can draw diagrams of these cells and label them. Similar structure (nucleus) has been observed in the onion peel cells.
Nucleus
6
0,
o
Cell membrane /
o \
Cytoplasm
I
(B) Nucleus
Fig. 1.22 Cheek cell of humans
It is the most essential part of the cell which directs and controls all the cellular activities. It is compared to the control room of a factory. It was first discovered by
Robert Brown (1831). The nucleus is usually dense, spherical or oval in shape. It occupies a central position in the cell but it may be shifted to one side by vacuole as in plant cells. Nucleus is bounded by two membranes, both forming nuclear envelope. Nuclear envelope encloses a space between two nuclear membranes and is connected to a system of membranes called the Endoplasmic Reticulum (ER). The presence of nuclear envelope, separates the nuclear material from The Fundamental Unit of Life
19
the cytoplasm. Each nuclear membrane is about 90A thick and has a membrane structure similar to that of plasma membrane. The nuclear envelope is perforated at intervals by the nuclear pores. The nuclear envelope encloses the nuclear sap or nucleoplasm. Nuclear pores allow exchange of chemical substances between the cytoplasm and the nucleoplasm. Within nucleoplasm are present nucleolus and chromatin material. ~llcleolus may be one or more in number and are generally spherical. They are very large in cells that are active in protein synthesis. Their role is to synthesize and to assemble RNA (ribonucleic acid) molecules and numerous proteins that make up the ribosome. RNA is helpful in protein synthesis in the cytoplasm.
• A chromosome has two chromatids attached to a centromere. • Gene is formed of DNA.
Chromatin material is a thin thread-like structure which is composed of DNA (Deoxyribonucleic acid) and proteins (i.e., histones). During cell division, chromatin threads condense to form rod-shaped chromosomes. Each chromosome has two similar chromatids attached to a centromere. Chromatin material contains mostly DNA (deoxyribonucleic acid). It plays an important role in heredity, i.e., transmits hereditary information from one generation to the next. The quantity of DNA varies greatly in cells of different kinds of organisms. DNA stores all the information necessary for cell metabolism. Chromosomes: Structure and Number
Chromatids Chromatids Fig. 1.24 Structure of chromosomes
Chromosomes (Gr., chromo, coloured + soma, body) are thread-like dark stained bodies in the nucleoplasm of nucleus and discovered by W. Waldeyer in 1888. Chromosomes are messengers of heredity. Chromosomes are thread-like, thin, coiled, elastic contractile structures, known as chromatin threads. This condition of chromosomes is found in the interphase or resting stage ofthe cell. In the chromosomal matrix are found embedded two similar spirally coiled threads, called chromonemata (singular, chromonema). Each chromosome contains two symmetrical chromatids. Each chromatid contains a single D A molecule. The chromatids are attached to each other only by the centromere. Chromonema bears genes. Genes These are the functional units of DNA and are arranged in a single linear order along the DNA molecule. One gene controls one or more than one cell functions. Sometimes a single function is carried out by a set of genes. The chromosome number is constant for all species and is given in the following table: Table 1.3 Chromosome Number in Some Organisms Organisms Plants: Sunflower
Chromosome number in each body cell
Garden pea
34 14
Onion
16
Maize
20
Rice
24
Animals: Round worm (megalocephala) Round worm (A. lumbricoides)
24 The Fundamental Unit of Life
20 ---------- --
2
- -
-"'"
==~--~------------------
28
Silkworm Fruitfly
I
4
Housefly
I
12
Mosquito
I
6
Butterfly
I
446
Cockroach
I
24
I
100
Golden fish Frog
I
Toad Rat
26 22
I
42
Rabbit
44
Monkey
42
Human beings
I
46
Functions of Nucleus: (i) Nucleus controls all the metabolic activities of the cell. Ifthe nucleus is removed
from a cell, the protoplasm will ultimately dry up and die. (ii) Nucleus regulates the cell cycle (division of cells). (iii) It is related to the transmission of hereditary characters from parents to offsprings.
I
(C) Cytoplasm
When you observe the temporary mounts of onion peel and human cheek cells, you can see a large region of each cell enclosed by the cell membrane. This region takes up very little ·strain. It is called cytoplasm. The cytoplasm is the quasifluid, jelly-like mass of protoplasm excluding the nucleus and surrounded by plasma membrane. It is formed of proteins, nucleic acids, carbohydrates, lipids and certain inorganic substances. Many small organelles are found inside the cytoplasm. These are known as cytoplasmic organelles. Each of these organelles performs a specific function for the cell.
FORMATIVE ASSESSMENT FA 1.6 Multiple Choice Questions Select the right choice: 1. Chromosomes are made up of (a) DNA and protein (b) (c) DNA and RNA (d) 2. Gaseous exchange in cells takes place by (a) osmosis (b) (c) diffusion (d) The Fundamental Unit of Life
RNA and protein protein exocytosis endocytosis
21
3. Amoeba acquires its food through a process known as (a) plasmolysis
(b) endocytosis
(c) exocytosis
(d) both exocytosis and endocytosis
4. The process of plasmolysis in plant cell may be defined as (a) breakdown/bursting of plasma membrane in a hypotonic medium. (b) shrinkage of cytoplasm in hypertonic medium. (c) shrinkage of cytoplasm in hypotonic medium. (d) breakdown/bursting of plasma membrane in a hypertonic medium.
5. A cell may swell and even burst if (a) the concentration of water molecules within the cell is higher than the concentration of water molecules in the surrounding medium. (b) the concentration of water molecules in the surrounding medium is higher
than the concentration of water molecules within the cell. (c) the concentration of water molecules is same in the cell and in the surrounding medium. (d) it is a plant cell and surrounded by a hypotonic solution.
FA 1.7: True or False State whether the following statements are True or False. 1. In plant cells, a cell wall composed mainly of cellulose is located outside the cell membrane. 2. There is shrinkage of the cell content away from the cell wall, when a living plant cell loses water. This phenomenon is known as plasmolysis. 3. The cell will lose water by osmosis, if the surrounding medium has a higher concentration of water than the cell. 4. A chromosome has two chromatids attached to a centromere. 5. Nucleus is responsible for transmission of heredi.tary characters from parents to offsprings.
FA 1.8: Concept-based Worksheet What will happen to an animal cell or a plant cell when placed in a sugar or salt solution. One of the following three things could happen. 1. When the medium surrounding the cell has a higher water concentration than the cell, the cell will---'-_ 2. When the relative concentration of water and solutes on either side of the plasma membrane is the same then _ 3. If the medium has a less concentration of water and higher concentration of salt then the cell will
-----------------------
FA 1.9: If I Pretend yourself to be an animal cell and answer the following questions accordingly. 1. List out your characteristic features with an example. 2. Write down the name of your cell organelles. 3. Distinguish between a plant cell and your cell.
22
\\'Ie tunQamenta\ Unit G1 Li1e
~ ~'~Y"~'.1~t~jii~~tI£ FA 1.10: Activity-based Questions Prepare an experimental set-up consisting of two beakers. One beaker has water to which peeled pieces of carrot have been added. In the second beaker, saturated sugar/salt solution has been put in which peeled pieces of carrot have been added. Preaper this set-up and keep it for 6-8 hours or overnight before taking it to the class. Show the experimental set-up to the students explaining the content of each beaker and time duration for which carrots were immersed in the solution. Ask the students to observe the carrots in the two beakers and compare the physical state of the carrots carefully. Answer the questions given in the worksheet. 1. What is the difference in the physical state of the carrots as observed in the two . beakers?
2. Name the process involved that has caused a change in the carrot piece in one beaker. 3. Why has the above process occurred? 4. Name the type of solution in beaker A and B with respect to the carrot pieces? 5. Name one process in your daily life which works on the same principle.
Cell Organelles The cytoplasm of a cell contains a variety of organelles having tJ;leir permanent structures with definite functions. These are membrane-bound, such as mitochondria, lysosomes and peroxisomes. Cell organelles are the living parts of the cell found embedded in the cytoplasm. These are smaller in size and bounded by unit membrane like plasma membrane and thus, keeps its own contents separate from the external environment. Large and complex cells, including cells from multicellular organism, need a lot of chemical activities to support their complicated structure and function. To keep these activities of different kinds separate from each other, cells have developed membrane bound organelles within themselves. They form the living part of the cell and each of them has a definite shape, structure and function. Some of these organelles are visible only under an electron microscope. The important cell organelles are described below.
I
1. Plastids
Plastids are the largest cytoplasmic organelles bounded by a double membrane. These are found in most of the plant cells and in some photosynthetic protists. These are absent in prokaryotes and animal cells. Like the mitochondria plastids also have their own genetic material and protein synthesising machinery, (i.e., DNA, RNA) and ribosomes. They are self-replicating organelles like the mitochondria, i.e., they have the power to divide. These are of following three types: (a) Chromoplasts: Coloured plastids (b) Chloroplast (Green coloured plastids): They contain chlorophyll pigment. (c) Leucoplasts: Colourless plastids.
The Fundamental Unit of Life
23
-
Chloroplasts Nature and Occurrence
The plastids with green pigment, the chlorophyll, are called chloroplasts. These are present in green algae and higher plants. The presence of chlorophyll makes them of utmost biological importance. The chlorophyll enables the chloroplasts to harness kinetic solar energy and trap in the food substances in the form of potential energy. All living organisms directly or indirectly depend on them for obtaining energy. Therefore, chloroplasts are the 'kitchens of the cells'. Each chloroplast is bounded by two membranes. It shows two distinct regions.
Circular-~~~'--
DNA
(or matrix)
(a) Stroma: It is the colourless proteinaceous ground substance that fills the
chloroplast. It contains a variety of photosynthetic enzymes, starch grains, DNA and ribosomes. It is the site of dark reaction during photosynthesis. (b) Grana: These are stacks of membrane-bounded, flattened, discoid sacs containing chlorophyll molecules. These are the main functional units of chloroplasts. It is the site of light reaction during photosynthesis. Functions
. Photosynthesis is one of the most fundamental biological functions. By means ofchlorophyll contained in chloroplasts, the green plants trap the energy of sunlight and transform it into chemical energy. This energy is stored in the chemical bonds produced during the synthesis of various food stuffs, like starch, etc. Chromoplasts give colours to flowers and fruits which attract insects for pollination. Leucoplasts are involved in the synthesis and storage of various kinds of food in the form of starch, oils and proteins.
I
2. Mitochondria
The mitochondria (Gr. rnito = thread; chondrion = granule) are tiny structures of variable shapes; cylindrical, spherical, or rod-shaped and . . . , , - - - - - Ribosome the average size of mitochondria is 0.2 ,urn to 2 ,urn, distributed Outer membrane in the cytoplasm. These convert the potential energy of food stuff into kinetic energy and hence are commonly known . . . - - - - Inner membrane as the 'power house' of cell. These are essential for aerobic - - - Outer chamber respiration. ='!~--- Matrix
Ultra Structure ~~Dj~ =.,-------
DNA molecule
"ajliU~;,;~~t--- F 1 particle ::=::L~~==~--- Cristae
Fig. 1.26 Internal structure of Mitochondria
24
Under electron microscope, a mitochondrion appears as a double walled structure like an ice box of thermos bottle. It consists of an outer and inner membrane and enclosed within them are two compartments or chambers. The outer membrane is very porous. Inner membrane is folded into the matrix as an incomplete septa, called cristae (singular crista). These increase the surface area of the inner membrane and divide the inner chamber. The inner membrane (or M.face) is studded (dotted) with numerous spherical or knob-like elementary particles or The Fundamental Unit of Life
oxysomes. The inner cavity of mitochondria are filled with a homogeneous, gel-like (proteinaceous) matrix which contain a few small sized ribosomes, a circular DNA molecule and phosphate granules. Therefore, mitochondria are able to make sure of their own proteins. Mitochondria are absent in bacteria and red blood cells of mammals. Functions
Mitochondria are the respiratory organs of the cells. The carbohydrates and fats present in the cells are completely oxidized into CO 2 and H 2 0 with the help of enzymes present in the mitochondria. During oxidation, a large amount of energy is released which is used by the mitochondria for the synthesis of the energy rich compound, the adenosine triphosphate (ATP). Since they synthesize ATp, they are also known as power houses of the cell. This energy is used by the cell for performing various chemical activities.
I
3. Vacuoles
Vacuoles are sap-filled vesicles in the cytoplasm. These are found in all the eukaryotic cells. They are the kinds of storage sacs. In animals, a number of small size and temporary vacuoles are found which store water, glycogen and proteins. Its membrane is typically a single unit membrane and is associated with the maintenance ofwater balance (osmoregulatory organ in protozoans) or ingestion offood substance (food vacuole). Thus, in unicellular organisms such as amoeba and paramecium, the food vacuole contains the food items that the animal has consumed. Fig. 1.27
A plant cell has a single large vacuole which is permanent. In plant cells, the vacuole increases in size as the cell enlarges. The central vacuole of some plant cells may occupy 50-90 per cent of the cell volume. Due to the central position of the vacuole, the nucleus and other cell organelles are pushed near the boundary wall. In plants, the vacuoles are bounded by a single unit membrane called tonoplast. These are filled with a fluid, the cell sap. The cell sap is rich in minerals, sugars, amino acids, esters, water soluble proteins and waste products in solution or in the form of crystalline deposits. Functions (i) Cell sap of vacuoles maintains the turgidity of plant cells. (ii) This supports the green parts of the plant. (iii) Vacuoles playa key role .in growth by elongation of cells.
(iv) Vacuoles store water, minerals, and reserve food in the form of sugar.
I
4. Endoplasmic Reticulum (ER)
It is a network of fluid-filled interconnecting membranous tube like structures covering the most part of the cytoplasmic matrix. It occurs in three forms, cisternae (closed fluid-filled gas), vertical and tubules. The E.R. membrane is similar in structure to the plasma membrane. It communicates with the plasma membrane and also with the nuclear envelope. Endoplasmic reticulum is of two types: (a) Rough endoplasmic reticulum (RER): With its outer surface are attached
ribosomes which synthesize proteins. It is well developed in protein synthesizing cells, like pancreatic and liver cells. (b) Smooth endoplasmic reticulum (SER): It is continuous with rough ER. Its surface is smooth, devoid of ribosomes. It is found in glycogen rich regions. These secrete lipids. The Fundamental Unit of Life
--------
------~---
----
~~~~~.~~
~<>-~~<>-.
o-o I:"o~-o-<>o-~ ~
~::.~
Fig. 1.28 Endoplasmic reticulum (Rough)
25
Functions
The main functions of ER are as follows: (i) ER forms a network in cytoplasmic matrix, giving mechanical support to the (ii)
(iii) Fig. 1.29 Endoplasmic reticulum (Smooth)
(iv)
(v)
• Golgi bodies are secretory organelles. It secretes enzymes, mucous, pigments, etc.
cell. It functions as an intracellular transport system for various substances. ER collects synthetic products of cell and then transports them outside the cell. It also transports the RNA and nucleoproteins from the nucleus to the cytoplasm where protein synthesis occurs. Protein synthesis occurs on the surface of rough ER by ribosomes. These proteins are either used within the cell or exported outside the cell. Synthesis of lipids in collaboration with Golgi complex occurs on the surface of smooth ER. Synthesis oflipoproteins and glycogen occurs on smooth ER in liver cells. Smooth ER membrane contains enzymes for lipid synthesis and for lipid soluble drugs and other harmful compounds. These enzymes detoxify the above drugs and make them water soluble so that they may be excreted in unne.
15. Goigi Apparatus (Golgi Complex) Golgi apparatus was discovered by Camillo Goigi in 1898 in the cytoplasm of nerve cells. Morphologically, it is very similar in plant and animal cells. It consists of stacks of flattened disc-shaped bags or cisternae, and associated discharged secretory vesicles. It is a single large structure located in between the nucleus and pole of the cell in which secretion takes place, such as in thyroid cells, exocrine pancreatic cells and mucous cells of intestinal epithelium. In plant cells they are called 'dictyosomes'. Discharge vesicle
Golgi [ network _
Secretory vesicle Fig. 1.30 Goigi apparatus
Under electron microscope, Golgi comp Iex are mem b ranous fl attene d sacs (cisternae), tubules and vesicles and large vacuoles. Flattened sacs occur from 3 to 7 arranged in parallel rows, one above the other. Each stack of cisternae has a proximal forming a convex face closer to the nuclear envelope or ER and a distal or maturing concave face that encloses large secretory vesicles. Small transition vesicles or tubules are present upon Golgi cisternae. A large number of small vesicles which are associated with each Golgi stack transport proteins and lipids both to and from the Golgi apparatus.
Golgi complex is not found in bacteria, blue-green algae, sperms and red blood cells of mammals and other animals. The Golgi apparatus originates from smooth endoplasmic reticulum which in turn has originated from rough ER and finally becomes the Golgi cisternae. Functions (i) Golgi complex is the secretory organelle of the cell and transports the
substances (pancreatic enzymes, mucous secretions, secretion of mammary glands, thyroxin, pigments, etc., outside the cell) as well as intracellularly (within the cell). For export, secretion is packaged into vesicles, which are detached and form flattened sacs transported across the cell membrane.
26
The Fundamental Unit of Life
(ii) During cell division, Golgi complex forms the cell plate. (iii) Synthesis of cell wall, plasma membrane, and peroxisomes occur from Golgi apparatus. (iv) Acrosome of sperm is formed by the Golgi apparatus. Camillo Golgi Camillo Golgi was born in 1843 at Cartano near Brescia. He studied medicine in the University of Pavia. He graduated in medicine in 1865 and worked in the Hospital of St. Matleo in Pavio. In 1872 he became the Chief Medical officer in a hospital at Abbiate Grasso. He worked on nervous system in a little kitchen of the hospital turned into a laboratory. He developed a method of staining individually nerve and cell structures, which was called as black reaction. He used weak solution of silver nitrate to trace the ramifications Camillo Golgi of nerve cells. Throughout his life he continued to work on these lines, modifying and improving this technique. In recognition of his work, he got some highest honours and awards. He, along with Santiago Ramony Cajal, got the Nobel Prize in 1906 for their work on the structure of nervous system.
I
6. Ribosomes
In prokaryotic cells, ribosomes are always found free, but in eukaryotic cells, these are found either free in or attached on the rough ER. Ribosomes are also found in mitochondria and chloroplasts of eukaryotic cells. These are dense and rounded granules visible only under electron microscope. Ribosomes contain RNA and proteins. Lipids are not found in ribosomes. Function
Ribosomes are the sites where proteins are synthesized.
I
7. Lysosomes
Ribosome
Endoplasmic membrane Fig. 1.31 Protein synthesis on the ribosome of RER
Lysosomes are tiny spherical sac-like structures of cyroplasm. Each lysosome having a single limiting unit membrane contains powerful hydrolytic enzymes. These enzymes are capable of digesting all organic materials. These enzymes are synthesized in the RER which are brought to the golgi complex. Lysosomes are formed by the Golgi complex. Functions (i) Lysosomes are involved in digestion of microorganisms like bacteria, etc.,
(ii) (iii) (iv)
(v)
• Lysosome contains digestive enzymes, for the digestion of foreign material and their own damaged cell.
entering the cell by phagocytosis. Lysosome can digest the organic substances of the same cell in which it belongs. This process is called autolysis. Hence, lysosomes are called digestive bags. The dead or damaged cells are also digested by the enzymes released from the lysosomes of the same cells. Hence, these are called suicidal bags. For digestion in the cell, the material to be digested is surrounded by a membrane forming an endosome. It fuses with the lysosome, enzymes of which digest the contents of endosome. Lysosomes initiate cell division.
The Fundamental Unit of Life
27
I • Oxidative reactions occur in peroxisomes with the help of oxidative enzymes.
8. Peroxisomes
Peroxisomes are ovoid granules surrounded by a single membrane. They are found in abundance in liver and kidney cells. They contain certain oxidative enzymes and carry out some oxidation reactions. Functions (i) They help in the removal of toxic substances. (ii) They help in lipid metabolism and convert fat into carbohydrates.
I
9. Centrosome
The term centrosome was given by T. Bo\'eri in 1888, meaning central body. It is found only in animal cells and is generally absent in cells of plants. Each centrosome contains two rod-shaped granular structures called centrioles: It is not bounded by any membrane and are made up of microtubules. In plant cells, polar caps are present which function as centrioles. Functions Fig. 1.32 Centriole
(i) From the centrosome spindle fibres r~diate as an aster in animal cells and
lower plants. At the time of cell division, centrioles separate and migrate to opposite poles of the cell and then spindle is formed in between them, which help in cell division. (ii) In plant cells, polar caps are involved in the formation of spindle. Each cell, thus acquires its structure and ability to function because of the organization of its membrane and organelles in specific ways. As a result, each type of cell got a basic structural organization. This helps the cell to perform functions like respiration, obtaining nutrition and cleaning of waste material, or forming nerve proteins. Thus, the cell is the fundamental structural functional unit of life. This conclusion forms the essence of the cell theory. Table 1.4 Differences between Animal and Plant Cell Features
S.No.
I
Animal Cell
Plant Cell
l.
Size
Generally small
Larger thap animal cell
2.
Cell wall
Absent
Present
3.
Plastids
Absent
Present
4.
Vacuoles
Small, many and temporary Permanent and large, filled with cell sap occupying the centre of the cell.
5.
Golgi apparatus
Present near nucleus
6.
Centrioles
Present and called dictyosome.
I Present within centrosome
Absent. Polar caps are present.
FORMATIVE ASSESSMENT FA 1.11: Multip e Choice Questions Select the right choice 1. Which one of the following is called the 'digestive bag or suicidal bag'?
28
(a) Centromere
(b) Lysosome
(c) Nucleus
(d) Mitochondria The Fundamental Unit of Life
2. Which one of the following is not a function of vacuole? (a) Storage (b) Providing turgidity and rigidity to the cell (c) Locomotion (d) Waste excretion
3. The cell organelle involved in forming complex sugars from simple sugars are (a) endoplasmic reticulum
(b) ribosomes
(c) plastids
(d) golgi apparatus
4. The power house of a cell is (a) chloroplast
(b) nucleus
(c) mitochondria
(d) golgi apparatus
5. Which of the following statement is not related to endoplasmic reticulum? (a) It acts as a channel for the transport of materials between various regions of the cytoplasm. (b) It functions as a cytoplasmic framework providing a surface for some of
the biochemical activities of the cell. (c) Ribosomes are the sites of protein manufacture.
(d) It can be the site of energy generation.
FA 1.12: Complete the Data Complete the data given in the following table. Features
Cell wall
Animal cell
I
Plant cell
I
Present
Plastids Vacuoles
Small, many and temporary
Permanent, filled with of the cell. occupymg
Goigi apparatus
Present near
Present and called
Centrioles
Present within
Absent and
are present.
FA 1.13: Diagram-based Worksheet Give below are the figures representing plant and animal cells. Label any five organelles common in both plant and animal cells.
Tile Fundamental Unit of Life
29
FA 1.14: Mapping Type Worksheet
SUMMARY I I I
I
I
I I I I I I I
I I
30
Cell was first observed by Robert Hooke in a piece of cork in 1665. Anton von Leeuwenhoek discovered free bacteria and red blood cells and observed their inner organisation. Cell theory: Cell is a mass of protoplasm limited in space by a cell membrane and possessing a nucleus. Cell is the unit of life. Cell theory was discovered by Schleiden and Schwann. Cells originate from the pre-existing cell. Cell shape may be fixed like Paramecium or variable like Amoeba. A cell is bound by selectively permeable membrane, the plasma membrane and contains a nucleus and cytoplasm. Nucleus is also bounded by a nuclear membrane enclosing nucleoplasm. Cell membrane is selectively permeable allowing ions to move in and out. It is composed of double layers of lipids and proteins. In plants, cell wall lies outside the plasma membrane. It is composed of cellulose. Cell wall is lacking in animal cells. Cytoplasm contains a number of cellular organelles, such as nucleus, endoplasmic reticulum, ribosomes, Golgi complex, Iysosomes, peroxisomes, mitochondria, plastids, and centrosome. Nucleus is found in all cells and is bound by nuclear envelope (perforated) and encloses nuclear sap. Nucleus contains nucleolus and chromatin material (chromosomes). Endoplasmic reticulum is a branching tubular system found in cytoplasm and connected with nuclear envelope and plasma membrane. It functions as an intracellular transport system and synthesis of proteins on the RER. Ribosomes are the sites where protein synthesis occurs. Golgi apparatus originate from ER and contain various cellular secretions. Golgi apparatus in plant cells is called dictyosome. Lysosomes develop from Golgi apparatus and contain digestive enzymes. Mitochondria are the sites for cellular respiration. ATP is produced in them and hence is called the powerhouse of cells. Mitochondria are not found in prokaryotic cells and red blood cells. Plastids are found in plant cells. Chloroplasts, a type of plastid, help in photosynthesis. Plastids are of three types-chloroplasts (green), chromoplasts (coloured-other than green) and leucoplasts. Chloroplasts help in the photosynthesis. A chloroplast is formed of a number of grana. A granum is formed of a number of flattened discs arranged in a pile to form thylakoids. Thylakoids possess chlorophyll. Centrosomes are found only in animal cells. They initiate and regulate the chromosomal movement. Vacuoles are fluid-filled membrane bound structures, found in plant cells. Only protozoans (animals) possess temporary vacuoles. Vacuoles help in maintaining the osmotic pressure of cells. The Fundamental Unit of Life
FORMATIVE ASSESSMENT FOR PRACTICE FA 1. Wordplay Write the wordplay using the word below.
Awordplay is one where you choose a word or name and use each letter in the name as the beginning of a word or line that says something about that person or topic. Example: Awordplay using the word "SUN". Sometimes when we go to the beach, we get sunburnt. Usually, if I put sunblock on my skin, I do not get burnt. Noon is when I'm really prone to burn.
p-----------------------------
L
_
A
_
S
_ .,.---
T
_
1
_
D
_
S
_
FA 2. Young Scientist To prepare a temporary mount of onion peel You will need: Onion bulb, forceps, watch-glass with water, a glass slide, dropper, coverslip, safranine solution, microscope, etc. o Take a small piece of onion bulb. o
Peel off the skin from the concave side of the onion with the help of a pair offorceps.
o
Put the skin immediately in a watch-glass containing water to prevent it from getting folded or dry.
"'-I
o
Transfer the peel from watch-glass onto the glass slide.
o
Now, put a drop ofsafranine solution on this piece using a dropp,,/ollowed by coverslip.
o
Place the slide on the microscope stage for obseroation.
Results: o
You will obsen}e that the peel consists of
The Fundamental Unit of Life
_
31 _
FA 3. Flow-chart Based Worksheet Instructions: Given below is an incomplete flow-chart on cell organelles. • •
Some boxes/spaces in the flow-chart have been left blank. Complete the flow-chan adding terms/names/functions as and where required. Cell Organelles
Mitochondria
Endoplasmic Reticulum
Has ribosomes attached to membranes
No ribosomes attached to membranes
Plastids
Suicide bags
Packaging of products
of the cell
Not present in
Produce
AlP
Known as
Have their own
Produces
Storage sacs for solid or liquid contents
Produces
FA 4. Word Box Topic: Cell Directions: Complete the paragraph given below choosing appropriate words from the word box in the space provided. eukaryotes
Robert Hooke
plasma membrane
present
absent cork slice
Cells were first discovered by
selectively permeable prokaryotes In
observed the cells in a
1665. He
with the help ofa primitive
microscope. Organisms with cells in which the nuclear material is not bounded by a definite nuclear membrane are called
. While the advanced and complete cell in
which the nucleus has a definite nuclear membrane is called
_
In a prokaryotic cell, most of the other cytoplasmic organelles are
however they
are
in eukaryotic cells.
The outermost covering of the cell that separates the contents of the cell from its external environment is called
It prevents and allows
entry and exit of only limited materials In and out of the cell. Therefore, it is called __________________ membrane.
32
The Fundamental Unit of Life
FA 5. Seminar Topic: Nucleus Directions: The students may divide themselves into a group of eight to ten for a collective research/study on the given topic. The topic can be divided into following sub-topics for presentation. • • •
Discovery of nucleus StruclUre of nucleus Chromatin material
FA 6. True or False State whether the following statements are True or False. 1. Most malUre plant cells have a large central vacuole that helps to maintain the lUrgidity of the cell and stores important substances including wastes. 2. Plastids are present only in plant cells and also have their own Dl\A and ribosomes. 3. The smooth endoplasmic reticulum helps in the manufacture of fat molecules or lipids important for cell function. 4. Lysosome contains digestive enzymes for the digestion of foreign material and their own damaged cell. 5. Vacuoles are secretory organelles which secrete enzymes, mucous, pigments, etc. 6. Rough endoplasmic reticulum has smooth surface and is devoid of ribosomes. 7. Mitochondria are said to be the powerhouse of the cell as ATP is generated in them.
FA 7. Concept-based Worksheet The cytoplasm of a cell contains a variety of organelles having their permanent structures with definite function. These are membrane-bound, such as mitochondria, Iysosomes, peroxisomes, endoplasmic reticulum and vacuoles. Instructions: On the basis of above information provided in the book answer the following questions. 1. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?
2. 3. 4. 5. 6.
Describe the structure and function of Golgi apparalUs. Why are lysosomes also known as 'scavengers of the cells'? vVrite the site where ATP synthesis takes place in mitochondrion. Define chromoplasts, chloroplasts and leucoplasts. Write down the main functions of vacuoles.
FA 8. Multiple Choice Questions Select the right choice. 1. Which of the following can be made into crystal? (a) A Bacterium (b) An Amoeba (c) A Virus (eI) A Sperm
The Fundamental Unit of Life
33
2. A cell will swell up if (a) The concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding tnediurn (b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell (e) The concentration of water molecules is same in the cell and in the surrounding medium (d) Concentration of water molecules does not matter 3. Chromosomes are made up of (a) DNA (b) protein (e) D A and protein (d) R A 4. Which of these options are not a function of Ribosomes? (i) It helps in manufacture of protein molecules (ii) It helps in manufacture of enzymes (iii) It helps in manufacture of hormones (iv) It helps in manufacture of starch molecules (a) (i) and (ii) (b) (ii) and (iii) (e) (iii) and (iv) (d) (iv) and (i) 5. Which of these is not related to endoplasmic reticulum? (a) It behaves as transport channel for proteins between nucleus and cytoplasm (b) It transports materials between various regions in cytoplasm (e) It can be the site of energy generation (d) It can be the site for some biochemical activities of the cell 6. Following are a few definitions of osmosis Read carefully and select the correct definition (a) Movement of water molecules fi'om a region of higher concentration to a region of lower concentration through a semipermeable membrane. (b) Movement of solvent molecules from its higher concentration to lower concentration (e) Movement of solvent molecules fi'om higher concentration to lower concentration of solution through a permeable membrane. (d) Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane. 7. Plasmolysis in a plant cell is defined as (a) break down (lysis) of plasma membrane in hypotonic medium (b) shrinkage of cytoplasm in hypertonic medium (e) shrinkage of nucleoplasm (d) none of them 8. Which of the following are covered by a single membrane? (a) Mitochondira (b) Vacuole (e) Lysosome (d) Plastid 9. Find out the false sentences (a) Golgi apparatus is involved with the formation oflysosomes (b) Nucleus, mitochondria and plastic have DNA; hence they are able to make their own structural proteins. (e) Mitochondria is said to be the power house of the cell as ATP is generated in them. (d) Cytoplasm is called as protoplasm
34
The Fundamental Unit of life
,..
J,.,. ~.
10. The proteins and lipids, essential for building the cell membrane, are manufactured by (a) rough endoplasmic reticulum (b) golgi apparatus (e) plasma membrane (d) mitochondria 11. The undefined nuclear region ofprokaryotes are also known as (a) nucleus (b) nucleolus (e) nucleic acid (d) nucleoid
12. The cell organelle involved in fonning complex sugars from simple sugars are (a) endoplasmic reticulum (b) ribosomes (e) plastids (d) golgi apparatus 13. Which out of the following is not a function of vacuole? (a) Storage (b) Providing turgidity and rigidity to the cell (e) Waste excretion (d) Locomotion 14. Amoeba acquires its food through a process, termed (a) exocytose (b) endocytosis (e) plasmolysis (d) exocytosis and endocytosis both 15. Cell wall of which one of these is not made up of cellulose? (a) Bacteria (b) H)'drilla (e) Mango tree (d) Cactus 16. Silver nitrate solution is used to study (a) endoplasmic reticulum (b) golgi apparatus (e) nucleus (d) mitochondria 17. Organelle other than nucleus, containing DNA is (a) endoplasmic reticulum (b) golgi apparatus (e) mitochondria (d) lysosome 18. Kitchen of the cell is (a) mitochondria (b) endoplasmic reticulum (e) chloroplast (d) golgi apparatus 19. Cell arises from pre-existing cell was stated by (a) Haeckel (b) Virchow (e) Hooke (d) Schleiden 20. Cell theory was given by (a) Schleiden and Schwann (b) Virchow (e) Hooke (d) Haeckel 21. The only cell organelle seen in prokaryotic cell is (a) mitochondria (b) ribosomes (e) plastids (d) lysosomes 22. Organelle without a cell membrane is (a) ribosome (b) golgi apparatus (e) chloroplast (d) nucleus 23. l!.tm is (6,) 10-6 m (b) 10-9 ill (e) 10- 10 m
24. Living cells were discovered by (a) Robert Hooke (01) Leeuwenhoek The Fundamental Unit of Life
(d) 10-3 m (b) Purkinje (d) Robert Brown
35
VK Biology IX
Answers 1. (e)
2. (b)
3. (e)
4. (e)
5. (e)
6. (a)
7. (b)
8. (b)
9. (a)
10. (a)
11. (d)
12. (d)
13. (d)
14. (b)
15. (a)
16. (b)
17. (e)
18. (e)
19. (b)
20. (a)
21.(b)
22. (a)
23. (a)
24. (e)
FA 9. Oral Assessment Instructions: Give the answers carefully. 1. What is the function of the cell wallO
2. What will happen to a cell if its nucleus is removed? 3. Where are genes located? 4. What is plasmolysis? 5. Is the plant cell wall living or dead? 6. Do the plant cells contain centriole? 7. Which cell organelle is responsible for intracellular transport' 8. Which cell organelle is called the suicidal bag? 9. What are the main functions of vacuoles? 10. ""hat is the primary function of leucoplasts?
FA 10. Paper Pen Test 1.' Answer the following questions. (b) Do you agree that "A cell is a building unit of an organism"? (e) Why does the skin of your figures shrink when you wash clothes for a long time?
How are chromatin, chromatid and chromosomes related to each other? (e) How is bactirial cell different from an onion peel celIO if) What are consequences ofthe following conditions? (i) A cell containing higher water concentration than the surrounding medium. (ii) A cell having low water concentration an compared to its surrounding medium. (iii) A cell having equal water concentration to its surrounding medium. if) Name two organelles in the plant cell that contain their own genetic material and ribosomes.
(d)
2. Fill in the Blanks. (a) Cell theory was proposed by and _ (b) serves as channels for the transport of materials between vanous regious of the cytoplasm or between the cytoplasm and the nucleus. (e) are known as powerhouses of the cell. (d) lack any membranes and hence do not show characteristics of eye until they enter a living body and use its cell machinery to multiply. (e) is the packaging and despatching unit of the cell.
~--
36
The Fundamental Unit of Life
...
J1
.,'~
..-
,,~
3. Match the following. Column II
Column I
I
(a) Vacuoles
(i) Suicidal bags of a cell
(b) Nucleoid
(ii) Powerhouse of a cell
(c) Lysosomes
(iii) Bacteria
(d) Mitochondria
(iv) Storage sacs of a cell
(e) Food vacuole
(v) "ucleus
If) Chromatin material and nucleolus
(vi) Amoeba
4. True or False. (a) Lysosomes keep the cells clean by digesting foreign materials and worn out cell organelle. (b) Osmosis plays an important role in gaseous exchange between the cells as well as the cell and its external environment. (c) Prokaryotic cells have no membrane-bound organelles, their chromosomes are composed of only nucleic acids and they have only very small ribosome as organelle. (d) An undefined nuclear region containing only nucleic acids in eukaryotes is called a nucleoid. (e) Smooth endoplasmic reticulum detoxifies many poisons and drugs. 5. Multiple Choice Questions. (a) Lipid molecules in the cell are synthesised hy (i) smooth endoplasmic reticulum (ii) rough endoplasmic reticulum (iii) golgi apparatus (iv) plastids (a) Lysosomes arises from (i) endoplasmic reticulum (ii) golgi apparatus (iii) nucleus (iv) mitochondria (a) Select the odd one out. (i) The movement of water across a semipermeable membrane is affected by the amount of substances dissoh'ed in it. (ii) Membrane are made of organic molecules like proteins and lipids. (iii) Molecules soluble in organic solvents can easily pass through the membrane. (iv) Plasma membranes contain chitin sugar in plants. (a) Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell? (i) Golgi apparatus (ii) Lysosomes (iii) Smooth endoplasmic reticulum (iv) Vacuoles (a) Find out the correct sentence. (i) Enzymes packed in lysosomes are made through RER. (ii) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively. (iii) Endoplasmic reticulum is related to the destruction of plasma membrane. (iv) Nucleoid is present inside the nucleoplasm of eukaryotic nucleus.
The Fundamental Unit of Life
37
II'J!IiiiiIi I I Il"l
SUMMATlVE ASSESSMENT A. Textbook Questions 1. Who discovered cells and how? Ans. The cell was first discovered by Robert Hooke in 1665. He examined thin slices of cork under a self· made microscope and saw a multitude of tiny hollow spaces that he remarked looked like the walled compartments of a honeycomb. He termed these spaces as 'cell' meaning 'small room' in Latin. 2. Why is the cell called the structural and functional unit of life? Ans. All living organisms are made up of cells. This shows that the cell is the structural unit oflife. Each living cell has the capacity to perform certain basic functions that are characteristics of all living forms. For example, phagocytic cells eat or kill unwanted or foreign particles inside the body (e.g., WBCs) some cells, e.g., pancreatic cells, small intestine cells, liver cells secrete enzymes and hormones. That is why cell is called the structural and functional unit of life. 3. How do substance like CO 2 and water move in and out of the cell? Discuss Ans. Carbon dioxide and water move across a cell by the process of diffusion and osmosis respectively. When the concentration of CO 2 is low outside the cell as compared to inside, it moves out, i.e., from a region of high concentration to a region oflow concentration. Also, when concentration of water increases inside the cell as compared to its exterior, it moves across the plasma region from a region of its high concentration to its low concentration. 4. Why is plasma membrane called a selectively permeable membrane? Ans. Plasma membrane is called selectively permeable membrane because it allows the movement of only selected molecules across it. 5. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.
Eukaryotic cell
Prokaryotic cell I. Size: generally small (1-10 /Lm)
I/Lm
=
1. Size: generally large (5-100 /Lm)
10-6 III
2. Nuclearregion:
_
and known as
2. Nuclear region: Well-defined and surrounded
_
by a nuclear membrane.
3. Chromosome: single
3. More than one chromosome.
4. Membrane-bound cell organelles absent.
4.
_
Ans. Eukaryotic cell
Prokaryotic cell I. Size: generally small (1-10 /Lm) I /Lm = lO-6m
2. l\uclear region: Undefined due
I. Size: generally large (5-100 /Lm) to
the
absence of nuclear membrane and known as nucleoid.
2. "Juclear
regIon:
Well-defined
and
surrounded by a nuclear membrane.
3. Chromosome: single
3. More than one eh romosome.
4. Membrane-bound cell organelles absent.
4. \lembrane-bound cell organelles (e.g., chloroplasts, Golgi bodies, etc.) present.
38
The Fundamental Unit of Lrte
....-:h
.....
~
6. Can you name the two organelles we have studied that contain their own genetic material? Ans. Plastids and mitochondria. 7. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen? Ans. Cell organelles are responsible for the organisation and proper functioning of a cell, as each of them perform some specific functions. 'Iaturally, if any of these organelles are destroyed, the functions of the cell will be stopped and it may also result in the death of the celL 8. Why are lysosomes known as suicidal bags? Ans. Lysosomes are known as 'suicidal bags' because when cell gets damaged during the disturbance in cellular metabolism, lysosomes may burst and the digestive enzymes thus released digest thei r own celL 9. Where are proteins synthesised inside the cell? Ans. Ribosomes present in the cell synthesise proteins and are called protein factories of the celL These may be attached on the surface of rough endoplasmic reticulum or lie freely in the celL 10. Make a comparison and write down ways in which plant cells are different from animal cells. Ans. The differences between plant cells and animal cells are as follows: Plant cells
Animal cells
I. Plant cells are larger in size.
I. Animal cells are comparatively smaller in size.
2. They contain cell wall made of cellulose. which IS present outside the plasma membrane.
2. Cell wall is absent. Only plasma membrane is present.
3. They contain plastids. t.e., chloroplasts. leucoplasts and chromoplasts.
3. Plastids are absent.
4. Centrosome is absent.
4. Centrosome is present.
5. Larger vacuoles are present.
5. Vacuoles either absent or are very small in Size.
6. Food is stored in the form of starch.
6. Food is stored in the form of glycogen.
7. Lysosomes are either absent or are very few in number.
7. More number of prominent Iysosomes are present.
11. How is a prokaryotic cell different from a eukaryotic cell? Ans. Differences between prokaryotic cell and eukaryotic cell are as under: Prokaryotic cell
Eukaryotic cell
L Prokaryotic cells are generally small in size. (1-IO!-L m ).
L Eukaryotic cells are comparatively larger in size (5-100 !-Lm).
2. The nuclear material is undefined having no nuclear membrane and is called nucleoid.
2. A true nucleus having a nuclear membrane is present.
3. A single chromosome is present.
3. :\1ore than one chromosome is presenL
4. It does nm contain membrane-bound cell
4. It contains membrane-bound cell organelles like mitochondria, plastids. etc.
organelles. 5. Ribosome is of 70S type.
5. Ribosome is of 80S type.
6. Cell division takes place by fission or budding or fragmentation.
6. Cell division lakes place by mitosis or meiosis.
The Fundamenlal Unit of Lde
39
':.,'i>d
.~
.
'.._
,~:
T>k,
-
~
12. What would happen if the plasma membrane ruptures or breaks down? Ans. Plasma membrane is the selectively permeable membrane that surrounds the cell and allows the entry and exit of selected materials of the cello If it ruptures, the contents of the cell will come in direct contact with the surrounding medium and not only unwanted material will be able to enter freely into the cell, but useful material will also find its way out of the cell easily. This will seriously disrupt the various metabolic activities of the cell and will result in its eminent death, 13. What would happen to the life of a cell if there were no Colgi apparatus? Ans. If there were no Golgi apparatus, the material synthesised by endoplasmic reticulum would not be carried to the various parts inside and outside of the cello Also as the Golgi apparatus performs the function of storage and modification of the material synthesised in the cell, these materials could not be stored and modified further Moreover, there will be no production of lysosomes which will cause the accumulation of waste material, viz., worn out and dead cell organelles within the cell which will ultimately lead to cell death. 14. Which organelle is known as the powerhouse of the cell? Why? Ans. Mitochondria are known as powerhouse ofthe cell because these are the sites ofcellular respiration. They release energy in the form of ATP (Adenosine Triphosphate) oxidation of carbohydrates and fats. This energy is then utilised by the organelles to carry out their basic functions. 15. Where do the lipids and proteins constituting the cell membrane get synthesised? Ans. Lipids are synthesised in smooth endoplasmic reticulum from where they are transported to the cell membrane. Proteins are synthesised by the ribosomes in the cytoplasm. These are then transferred to Golgi complex and ER for further modifications from where they reach their destinations. 16. How does an Amoeba obtain its food? Ans. In Amoeba, the food particles get surrounded by a cell membrane invagination called pseudopodia. The pseudopodia d,en merge with each other forming a food vacuole which is engulfed into the body of Allweba. These vesicles are called phagosomes where the food is digested.
1
Amoeba
T
Food particle
• Pseudopodia Phagosome
17. What is osmosis? Ans. The diffusion of water or solvent through a semi-permeable membrane from a solution of lower concentration of solutes to a solution of higher concentration of solutes is called osmosis. 18. Carry out the following osmosis experiment: Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water.
Now, (a) Keep cup A empty
(b) Put one teaspoon sugar in cup B. (c) Put one teaspoon salt in cup C. (d) Put one teaspoon sugar in the boiled potato cup D. -----Ilfj~';JIil~
.... ,.
~
40
The Fundamental Unit of life
Keep these for two hours. Then observe the four potato cups and answer the following: (i) Explain why water gathers in the hollowed portion of Band C. (ii) Why is potato A necessary for this experiment? (iii) Explain why water does not gather in the hollowed out portions of A and D. Ans. (i) Water gathers in the hollowed portion of Band C because of the process of endosmosis (moving in ofthe solvent). The potato wall acts as a semi-permeable membrane. As the cups Band C are filled with sugar and salt respectively and their outer part is in contact with the water, the concentration of water outside the cups is higher than inside the cups. So, water l110ves fronl its higher concentration towards the lower concentration, i.e., inside the cup.
I
Fresh peeled
I~
-"" \
~j CupA
CupS
Sugar
CupC
Cup 0
(ii) Potato A acts as a control of the experiment. It is very necessary for comparing the results
of the experiment. It shows that if the concentration of water is same on both sides, there will be no movement of water. (iii) Water does not gather in the hollowed out portions of A as it does not contain hypertonic
solution so there is no concentration difference and hence no movement of solvent. Water does not gather in the cup D as the cells of boiled potato are dead and the potato wall is no longer semi-permeable. Hence, no osmosis occurs.
HOTS (Higher Order Thinking Skills) 1. If you are provided with some vegetables to cook, you generally add salt into the vegetables. After adding salt, vegetables release water. Why? Ans. When salt is added, a hypotonic medium is created, i.e., the concentration of salt molecules is more outside the vegetables than inside. Hence, due to osmosis water from the vegetables come out. 2. If cells of onion peel and RBC are separately kept in hypotonic solution, what will happen to each of them? Explain. Ans. When kept in a hypotonic solution, the onion cells will become turgid because the water will enter the cell due to osmosis. But the cell wall present outside the cell provides it rigidity and does not let any harm to occur. Whereas, in RBC the movement of water inside the cell due to osmosis will lead to bursting of the cell because it does not have a rigid cell wall. 3. How will absence of anyone of the cell organelles affect the cell's working? Ans. Functions of all the organelles are inter-linked to each other and ultimately to the working of the example cell. So, if even a single link is missing, the cell ultimately suffers and dies. For e.g., DNA from the nucleus passes the information for protein formation to the ribosomes which send the proteins to Golgi complex and ER for modification and transport.
The Fundamental Unit of Life
41
4. Where will you find more number of ribosomes-in cancer cells or in fat cells? Ans. Ribosomes are found in greater number in actively dividing cells which are the cancer cells as they need more amount of proteins for the formation of new cells. 5. A solution of 3% glucose and a solution of 8% glucose are kept in a trough separated by a semi-permeable memhrane. What will you observe after I hour? Ans. After I hour, the solutions on both the sides of the semi-permeable membrane will become isotonic because of the process of osmosis.
EXERCISES A. Very Short Answer Questions
(1 m.ark)
I. Who first discovered the cell?
2. 3. 4. 5. 6. 7. 8. 9. 10.
11. 12. 13. 14. 15. 16.
Who discovered the cytoplasm and nucleus' Which type of cell is found in bacteria and blue-green algae? Write down the names of cell organelles of eukaryotic cells. What is the main characteristic of prokaryotic cell? Write down the full form of ATP Write the names of cell organelles. What are the three major functional regions of the cell? Is the cell wall living or dead in plants? Write down one main function of the following cell organelles: (a) Plasma membrane (b) Chloroplasts (c) Nucleus (d) Mitochondria (e) Nucleolus (j) Chromosomes (g) Ribosomes (h) Lysosomes (i) Goigi apparatus !j) Peroxisomes Is chloroplast a non-living structure? Name the nucleic acids present in the nucleus of an animal cell. What is the function of mitochondria' Which cell organelle releases the energy in the form of ATP? j arne the chemical molecule which carries the hereditary characters from parent to offspring. Do the plant cells contain a centriole?
B. Short Answer Questions
(2,3 marks)
I. Who coined the word 'cell' and how'
2. What is the cell theory? 3. Write down the names of cell organelles and describe the functions of any two. 4. Differentiate between: (a) Ribosome and centrosome, (b) Chromatin and chromosome, (c) Nucleus and nucleolus, (d) Haploid and diploid cells.
Tenlal Unit of life
5. What is the difference between cell wall and cell membrane? 6. What is a cell? Describe its shape and size.
C. Long Answer Questions
(5 marks)
1. Why are mitochondria called the power-house of a cell? Describe the structure and functions
2. 3. 4. 5. 6. 7. 8. 9.
of mitochondria with the help of suitable diagrams. What are the major types ofplastids? Describe the green plastids involved in photosynthesis. Describe the structure and functions of Golgi apparatus. What is digestive bag? Describe its structure and functions. Write down the names of two nucleic acids. What are their functions? What is gene and where is it found? Give its functions. What will happen if we put a plant or animal cell in a (a) hypotonic solution (b) hypertonic solution (e) isotonic solution? What is diffusion? How is it useful in living beings? Draw diagrams of different kinds of cells present in human body.
10. Describe the main parts of a typical cell with various functions of the parts.
D. Practical-based Multiple Choice Questions 1. In order to observe a slide under high power, a particular sequence is to be followed after adjustment of light with the help of mirror and condenser. Identify the correct sequence. (i) Focus the slide with the help of coarse adjustment (ii) Focus with the help of fine adjustment (iii) Put the slide on stage (iv) Rotate the nose piece, to place the objective with high power on the slide (a) (ii), (iv), (iii), (i)
(b) (iii), (i), (iv), (ii)
(e) (iii), (i), (ii), (iv)
(d) (iii), (ii), (iv), (i)
2. Rima of Class IX was asked to prepare the slides of onion peel and cheek cells in the lab but she was highly confused to see five different types of stains on the shelf of chemicals. As a helpful classmate, what stains would you suggest her to use for different slides? (a) Methylene blue for onion peel & safranin for cheek cells (b) Acito carmine for onion peel & janus green for cheek cells (e) Leishman stain for onion peel & eosin for cheek cells (d) Safranin stain for onion peel & methylene blue for cheek cells 3. Four students . Sharukh, Amir, Salman and Sanjay were provided with microscopes having different eye pieces and objective lenses. They were told to fit the eye piece and objective lens to get the magnified view of the object. Who do you think got the maximum magnification? (a) Amir selected objective of value 45X and eyepiece of value 5X (b) Shahrukh selected objective of value lOX and eyepiece of value 20X (e) Salman selected objective of value 40X and eyepiece of value lOX (d) Sanjay selected objective of value 20X and eyepiece of value 15X 4. An over enthusiastic student scrapped the inner side of his cheek to get a few epithelial cells with the help of a dissecting needle. Without feeling any pain, he could take out the cells and also prepared an excellent slide which fetched him full marks in his exam. He developed infection in his mouth after some time because (a) he must be having the infection before The Fundamental Unit of Life
43
(b) may be he pricked very hard (c) the needle was not sterilised
(el) all of the above
5. Following diagrams show the temporary mount of onion peel prepared by different student (A, B, C, D) of St. John's school. Who do you think was the most attentive student of this class as he followed all the instructions given by his biology teacher?
I I (a)
(b)
...-~
I
(c)
Ln
(d)
6. Many inquisitive students of Class VIII prepared a temporary mount of onion peel to look for a centrally located nucleus in a cell. They were disappointed when they could not see it. Their mistake was (a) not adding safranin on the peel (b) they took the outer peel instead of inner peel (c) nucleus is visible only under high power and they observed it only under low power (el) peel must have got overlapped reducing the contrast 7. Given below are the steps for the preparation of a temporary mount of onion peel. The steps are however not arranged in an order. Arrange them in a correct sequence. (i) Examine the slide under the microscope (ii) Put a cover slip, press it gently and clean the slide. (iii) Remove a thin transparent peel from a piece of onion. (iv) Transfer the peel on a clean slide with the help of brush and needle. (v) Put few drops of safranin stain in the watch glass to stain the peel. The correct sequence would be (a) (iii), (v), (iv), (ii), (i) (b) (v), (iv), (ii), (iii), (i) (c) (i), (ii), (iii), (iv), (v)
(el) (ii), (iv), (v), (i), (iii)
8. Given below are four operations for preparing a temporary mount of human cheek cells. (i) Taking scraping from inner side of the cheek. (ii) Putting a drop of glycerine on the material. (iii) Adding two or three drops of methylene blue. (iv) Rinsing the mouth with fresh water and disinfectant solution. The correct sequence of these operations is (a) (i), (ii), (iii), (iv)
(b) (iv), (i), (iii), (ii) (c) (iv), (i), (ii), (iii) (d) (i), (iii), (ii), (iv)
44
The Fundamental Unit of Life
9. Which of the following is a correctly labelled cell of an onion peel? Nucleus --.
Cell membrane Cell wall Vacuole
......
,
'-~
-
/
=fis-.--~ '
.,:
Nucleus '-~
!
.'----..'.6 0
,
, !
'._. _.. '
-
,-Cellwall
~cell
:
membrane
'
Vacuole
(b)
(a) Nucleus--, Cell wall
Gell membrane
~'---'-.
'
:
'
'. -" --- .-'
Nudeus-,
J0
-Vacuole
~o
.
Vacuole
(c)
. . . . .iceRwaJl .
(d)
10. Arrange the following steps in correct sequence. (i) Putting a drop of glycerine on the cheek cells on a slide. (ii) Scrapping the inner side of cheek (iii) Adding methylene blue stain, and (iv) Placing the cover slip over the material. (a) (i), (ii), (iii), (iv)
(b) (ii), (i), (iv), (iii)
(e) (iv), (ii), (iii), (i)
(d) (ii), (iii), (i), (iv)
II. Nikita observed a slide of human cheek cells under a microscope in its (i) low magnifying power, (ii) high magnifying power settings. In the first setting, she must observed (a) fewer cells in a darker field of view (b) more cells in a brighter field of view (e) more cells in a darker field of view (d) fewer cells in a brighter field of view. 12. To observe cells in an onion peel, we must prepare the slide by mounting on it (a) crushed pulp of onion (b) dry scale leaf (e) green leaf of onion (spring onion) (d) thin layer of Oeshy leaf of onion. 13. Human cheek cells stained in methylene blue and mounted in glycerine were observed with the help of a compound microscope. The components of the cell which would be seen are (a) Cell wall, cytoplasm, nucleus (b) Plasma membrane, cytoplasm, nucleus (e) Plasma membrane, cytoplasm, nucleus, mitochondria (d) Plasma membrane, cytoplasm, nucleus, mitochondria, golgi body, lysosomes. 14. Trupti was observing an onion peel stained with safranin under a microscope. The colour of the cell wall appeared (a) deep blue. (b) black (r) pinkish red (d) "dim,'. 15. Nucleus in eukaryotic cells is centrally positioned because vI) it is lhe regulatioll
Cl'llIre
orlhe cell
n'\--"
(II)
it conlitins
(r)
it has to send the illii.JrIlI;tlioll L'qll~t1I~ ill all dinTlioll ... it rt'q(lirl'~ Illaxilllllill protcnioll duc 10 ih kL'\ fiIIH·li(JJl~
(rI)
The Fundamental Unit of Life
45
16. Excess of stain from the slide can be removed by (a) using a muslin cloth (b) using a blotting paper (e) using a polythene (d) using a handkerchief 17. Which of the following organelles is not visible in the slide of onion peel even under high power? (a) Cell membrane (b) Cytoplasm (e) Cell wall (d) Mitochondria 18. Maximum light passes through the microscope when (a) aperture is closed and objective is 40X (b) aperture is open and objective is 40X (e) aperture is open and objective is lOX (d) aperture is partially open objective is 40X 19. The scientist, who invented the first compound microscope was (a) Zacchrais Janssen (b) Leeuwenhoek (e) Knoll and Ruska (d) Robert Hook 20. If cheek cells are placed in 10% salt solution, they will (a) absorb water and salt and become bigger in size (b) no change will occur (e) shrink as the cells will lose water due to exosmosis (d) cells will die 21. Which of the following liquids is not used in the preparation of stained temporary mount of onion peel? (a) Water (b) Glycerine (e) Safranin (d) Methyl alcohol 22. Pick the odd one out. (a) Plastids (e) Cell wall
(b) Large vacuoles (d) Centrioles
Answers 1. (b)
2. (d)
3. (e)
4. (d)
5. (a)
6. (b)
7. (a)
8. (b)
9. (b)
10. (d)
11. (b)
12. (d)
13.(b)
14. (e)
15. (d)
16. (b)
17.(b)
18. (b)
19. (b)
20. (e)
21. (d)
22. (d)
III
The Fundamental Unit of LITe
Chapter: Two
UDs)s)lliJ~s)
In the earlier chapter, it has been described that all living organisms are made of cells. A unicellular organism, such as Amoeba, Pammeciurn, has a single cell in its body. The single cell performs all the life activities, e.g., movement, intake of food, digestion, respiration, reproduction and excretion, etc. But in multicellular organisms there are millions of cells. Most of these cells are specialised to carry out a few functions. Each specialised function is taken up by a different group of cells. These cells function very efficiently. Thus, cells of multicellular organisms show division of labour. For example, in human beings, muscle· cells contract and relax to cause movement. Nerve cells carry messages. Blood cells carry oxygen and CO 2 , In plants, vascular tissues (xylem and phloem) conduct water and food. So, we see that cells, that are specialised in one function, are grouped to form a tissue. Blood, muscles, xylem and phloem are all examples of tissues.
• A tissue is a group
of cells having a common ongm,
similar structure
and specialised to perform a common
function.
A tissue is defined as a group of cells of common origin having similar structure and specialised for performing a common function. In the beginning, all the cells are alike but as development proceeds, a change occurs in their size, structure and functions; this differentiation of cells is followed by the formation of different kinds of tissues. Thus, a tissue is a cluster of cells at a definite place in the body performing a special function. A group of tissues of different types work in harmony to form organs.
I
Are Plants and Animals Made of Same Type of Tissues?
Plants and animals are two different organisms. Plants are autotrophic organisms, i.e., they prepare their own food by the process of photosynthesis. Moreover, plants are stationary or fixed, i.e., they do not move about except for a few unicellular algae. Hence, they do not consume or need much energy, therefore, most of the tissues of plants are supportive, that provide them with structural strength. Most ofthese tissues like xylem, phloem, sclerenchyma and cork are dead, i.e., they do not contain living protoplasm. On the other hand, animals are heterotrophic organisms. They move from place to place in search oHood, mate and shelter. Therefore, they need more energy as compared to plants. Most animal tissues contain living cells. There are some tissues in plants that divide throughout their life. Tissues divide for the growth hand reproduction of plants. Such tissues are localised in certain regions. Based on the dividing capacity of the tissue, the various plant tissues can he classified as meristematic tissue and permanent tissue. On the other hand, there is no such distinct region in animals. Cell growth in animals is more uniform. So, there is no such demarcation of dividing and non-dividing regions in animals.
Tissues
47
Plant Tissues Plant tissues have been classified into two main groups: growing or me.ristematic tissues and permanent tissues. Growth in plants is restricted to certain regions. " Classification of Plant Tissues
I
t
\
l
Permanent Tissues (Mature cells incapable of cell diVision)
Meristematic Tissues (Cells are capable of cell division and have totipotency·)
l
f Apical (Tips of root \ and stem)
I
./
Lateral (Below bark, cambium. in dicot roots \ and stems)
t Intercalary (Internodes of stem) J
l
f Simple (Protective and supporting tissues composed of similar type of cells)
Complex (Conducting tissue composed of more than one type of cells)
I
Phloem 1. Sieve lubes 2. Companion cells
Parenchyma
Collenchyma ·Totipol~t I'G'riOIl$
I
ulh an fiJjJGbf~ of rrins:
uU t'ftWs
ris~ 10
Xylem 1. Xylem vessels 2. Tracheids
0.8 Ih
of th~ body':! an f1rgQ~~s~"---
-.
oJ
Sclerenchyma
A. Meristematic Tissues
These are found in the growing regions of the plant, e.g., shoot tip, root tip and cambium. Their cells are immature and are capable of undergoing repeated division throughout their life. These cells are spherical, oval, polygonal or rectangular in shape. Their cytoplasm is dense, cell ,,·all is thin, nucleus is single and large, and vacuoles (single or few or no vacuoles) if present are smaller. I ntercellular spaces are lacking. This tissue continuously forms a number of new cells. Classification: According to their position on the plant body, they are of the following types: (a) Apical meristem,
(b) Lateral meristem, (e) Intercalary meristem. Apical meristem
(a) Apical meristem: It is found at the growing tips of stems (shoot) and
Ir.tercalary meristem
roots. Its cells are roughly spherical, alike and divide continuously to form new cells which later differentiate into epidermal tissue, ground tissue (cortex) and vascular tissue (vascular bundles). Thus, the root and stem of a plant grow in length (primary growth). Root tip is protected by a root cap formed of a layer of cells. It protects the root tip from IIlJury.
lateral meristem
(aJ (b) Fig. 22 Seeuun through (a, stem ape) ar.d b!
root lip showing rnerislemallc
JSSlM
Fig.2.1 Menstems based On poslbon
iiiIIillI
48
Tissues
(b)
- - Dermatogem (epidermis)
Plerome ·--';---'----.!-(vascular bundles)
Cellwal
-F--Periblem (cortex)
FIg. 2.4 1.5. of the growing tip of root
Fig. 2.3 L.S. of stem tip
(c) Intercalary meristem: It is a part of the apical meristem, which is separated
from the apex during the growth. It is found at the base of the leaves or internodes (on either side of the node on twigs). In grass and bamboo, they are found near the nodes. They increase the length of the organ.
activity 1 • • • • • •
Take two glass jars, A and B, fill thern with water. Take two onion bulbs and place one onion bulb on the rnouth ofeach jar (as shown in Fig. 2.5). Obseroe the gTOwth of roots in both the onion bulbs for a few days. Measure the length of roots on day 1, 2 and 3. On day 4, cut the tips (about 1 crn part) of roots in one bulb ofjar A. Again obseroe the growth of roots in both the jars and rneasuTe thei,· lengths each day for five lIlore days and record yOUT observation in the following table: Length of root
Day 1
Day 2
Day 3
Day 4
Day 5
I. Jar A
2. Jar B
JarA
Fig. 2.5 Growth of roots in
onion bulbs
• PrOlll the above observation, answer the following questions: (i) Which of the jars has longer roots? Why? (ii) Do the roots continue l5'·owing even when you have Temoved theiT tips? (iii) Why do the TOot tips stop growing in jaT A after you have cut them? • Roots of onion bulbs in jaT B will continuously grow and will become 10ngeT because they have dividing cells at the TOot tip. In jar A, theTe will be no growth in onion bulb roots, since they lack the dividing cells. Cut TOots stop l5'·owing in jar A since thel"/! is no dividing tissue p,·esent. What happens to the cells formed by the meristematic tissue? They take up a specific role and lose the ability to divide. Thus, they form a type of permanent tissue. This process of taking up a permanent shape, size and function is called differentiation. In this way, the cells of meristematic tissue differentiate to form different types of permanent tissues. To understand the structure and function of various types of permanent plant tissues, YOil have to study the anatomy (Greek; ana = up; ternnein = to cut) of plant organs like roots, stem, leaves, flowers, etc. Tissues
Jar8
49
-.---.--~J11
activity 2 • • • • • • •
Take a small po,-tion of a sunfloweT stem. Keep it in wate,- in a watch glass. Cut its very thin sections with the help of mzo,- 0,- blade. Now, stain the slices with safranin. Tmnsfe,- one neatly cut section on a slide, and put a d,-op ofglycerine. COVeT it with a cover-slip and obseroe under a micTOscope. You will obseroe diffe,-ent kinds of cells and thei,' m-mngement. Compa,-e it with Fig. 2.6. Trichome Mucilaginous canal ~---
Cuticle
Epidermis
~;:::::= Hypodermis ~ Cortex
--'
I±!!L---_ Endodermis Pericycle--~
Fig. 2.6 Section of a stem
On the basis ofyour observation, try to find out the answer to the following questions: (i) Are all cells similar in structure?
(ii) How many types of cells can be seen? (iii) Can you think of reasons why there would be so many types of cells? You will find that the section of sunflower stem contains seven different types of cells and all these cells perform different functions such as, xylem (conducting water), phloem (transport of food), epidermis (protection), collenchyma, sclerenchyma (support), parenchyma (food storage), and cambium (growth). Thus, from the above activity, you have learned that different groups of cells of tissues present in a plant organ help to perform different functions. You can also try to cut sections of stems and roots of different plants and study them.
I B. Permanent Tissues These are derived from the meristematic tissues. Cells formed from the division of meristematic tissues, after maturity form permanent tissue. Their cells do not divide further. They gradually become specialised. They have a definite shape and may be living or dead and thin or thick walled. Their cytoplasm is vacuolated. Permanent tissues are of two types: simple tissue and complex tissue.
.---_....._--. Permanent Tissue
Simple
Complex
..
Parenchyma
IIL3
'-
-'v
VK Biology IX
50
Collenchyma
..
.J-....~ Sclerenchyma
Xylem
Phloem
Tissues
1. Simple Tissues These are ofthree types: (a) parenchyma, (b)collenchyma and (c) sclerenchyma. (a) Parenchyma (Gr., pam, beside + enchyma, in-filling). Parenchyma is generally found in all plants. Its cells are living. Each cell has a thin cell wall of cellulose and encloses a dense cytoplasm +--- Cytoplasm Intercellular spaces which contains a small nucleus f - - - Nucleus and surrounds a large central vacuole. are Generally its cells rounded, oval, polygonal or spherical in shape. The cells have intercellular spaces filled • -=+--Vacuole with air. These cells are found in epidermis, cortex, pith, ~~~-"rt----lntercellular space pericycle, elc., of stems, roots, • • Primary cell wall leaves, flowers and fruits (in pulp). It is also found in xylem (b) (a> and phloem. FI9 2.7 I.a) 1S. of Parend1yma (b) L.S. of Parenchyma Functions (i) They function as a packing tissue, filling the spaces between other tissues. They maintain the shape and firmness of the plant due to turgidity (provide mechanical strength to the plant). (ii) Their cells store food materials such as starch stored in the parenchyma cortex of potato tuber. (iii) Parenchyma cells store excretory products such as gum, tannin, resins, crystals of inorganic waste, etc. (iv) Parenchyma in xylem and phloem conducts water and food material respectively. (v) Some parenchyma cells have the power to divide and form secondary meristems. (vi) Parenchyma called aerencl1\'ma in aquatic plants helps in aeration of tissues and in aquatic plant it also provides buoyancy to help them float. (vii) They also contain chloroplasts called chlorenclnma which are responsible for photosynthesis (formation of starch). (b) Callenchyma (Gr., Kalla, glue). Cells are oval or polygonal in shape and generally found below the epidermis of the dicotyledon stem and petiole (leaf stalk). They are closely packed together and hence, no intercellular spaces. Their cell walls are ---Endwall - - - Cytoplasm much thickened at the corners Primary celt wall (due to cellulose and pectin) (thickened at where a number of cells join corners) Nucleus together. The cells are living I Nucleus and vacuolated. Cell wall is -----L- Vacuole irregularly thickened due to which the plant becomes firm Chloroplast and elastic. Sometimes these cells contain chloroplasts. In ~i""~-~~---lntercel1ular herbaceous plants, it acts as a $;;'--- Cell wall space permanent mechanical tissue. It is absent in monocot stems, (al (b) roots and leaves. Fig. 2.8 la) TS. of Collenchyma Ib) L.S of Collenchyma
]f-------
L
J
t:--iI-_T.:;:iS:::.SU::::8.::..S ••• 1. . . . .- - .
..::51:..-';;;;;;;;;::=:":"mi'l
Functions: (i) Being flexible in nature, it provides tensile strengtb to the plant body. (ii) It provides mechanical support to the leaf where it occurs on both sides of
vascular bundles or as isolated patches. (iii) It renders suppleness to the various parts of the plant (leaf, stem). (iv) When chloroplasts are present it takes part in photosynthesis.
(c) Sclerenchyma: It is also a simple permanent tissue and provides mechanical In'l---Narrow lumen support to the plant. Lignified thick wall These are considerably thick-walled and lignified Simple with simple or bordered pit pair pits in their walls and are characterised by the absence of living protoplasts. On the basis of (a) (b) variation in form. structure, Fig. 2.9 :a'i IS. of ScIerenchyma (b) loS. of ScIerenchyma origin and development, these may be either fibres or sclereids (see Fig. 2.9). Fibres: They exist as long, narrow and pointed cells. They occur in groups, as sheets or as cylinders in various parts of tbe plant body in and around the vascular tissue, and may also develop below the epidermis a cylinder of supporting tissues in some older stems. Sclereids: Sclereids are very thick walled, hard and strongly lignified. They are mostly isodiametric, polyhedral, short and cylindrical. These are dead cells with very narrow cell cavities (lumen) due to excessive thickness of the cell wall. Sclereids may occur singly or in groups in stems, leaves, fruits and seeds. Fibres and sclereids are tbick-walled. The 'cells' consist of walls alone, for the cell contents die when the walls become thickened and impermeable, cutting off nutrients and water. The walls are composed oflayers of cellulose impregnated with lignin (a chemical substance which acts as cement and hardens them). Lignin, when combined with cellulose, resists stretching (has high tensile strength) and buckling (has high compressional strength). Often these walls are so thick that there is no internal space inside the cell. Function: (i) Protects the plant from stress and strain ofenvironmental forces like strong winds. (ii) Provides mechanical strengtb and rigidity to the plant.
(iii) Sclereids provide grittiness to the pulp of fruits.
Table 2. I Comparison of Collenchyma and Sclerenchyma Collenchyma
Scelerenchyma
I. Living cells.
\. Non-living cells.
2. Cytoplasm is present in the cells.
2. Cell's cytoplasm dries up on maturity.
3. Cell walls are formed of cellulose.
3. Cell's walls are lignified.
4. Cell wall thickening is not uniform, much 4. Cell wall thickening is uniform. thickened at corners. 5. Cell lumen is wide.
5. Cell lumen is narrow due to thickening of cell wall.
6. Gives mechanical support and elasticity to 6. Gives only mechanical support. the plant.
52
Tissues
activity 3 • • • • • • •
Take a freshly plucked leaf of Rhoeo plant. Stnitch its upper side and break it with applying pTeSsure. When breaking it, stretch gently so that some peel or skin projects out. Keep this peel in a pelridish filled with water. Add a few drops of safranin stain to it. After a few minutes transfer it onto a clean slide. Cover it with a cover-slip and obse11Je it under the micTOscope.
You will observe that this outermost layer of cells in leaves is a single layer. These form the peel of an organ, the epidermis. Ruptured epidermis Cork cells Protective Tissues L ~ l-' These tissues are usually present in the outermost layer of -----l J" J I ::'>. the plant body. This layer is one cell thick, covered with cutin. ~-z,. ] 1 k These tissues protect the inner tissue of the plant body. Example is i--<. ~ epidermis and cork (or phellem). J (a) Epidermis: It is present on the external surface on all the plant organs (e.g., leaves, flowers, stem and roots) in the form FIQ 2.10 Protective bssue of a layer. It is a protective layer. Its cells are like parenchyma and lack intercellular spaces. The epidermis is usually one cell thick but it is multilayered in some plants, like Ficus, NeTium and orchids. Some plants possess hypodermis below the epidermis. On the outer surface of epidermis, a waxy layer of cutin is present. It is called cuticle. It minimizes or checks Fig.2.11 Cuticle and few cells of epidermis the loss of water from the internal tissues and also protects the mechanical injury and invasion by parasitic fungi. It is not found in aquatic plants. Each cell possesses peripheral protoplasm, a nucleus and a large central vacuole. Their shape is variable. They are living cells like parenchyma. Stomata: In between the epidermal cells are present minute (~I~S~~) apertures, called the stomata. Each stoma (singular) is guarded -l. by two kidney-shaped cells called the guard cells. Guard Epidermal cells are the only epidermal cells which contain chloroplast, cell the rest being colourless. The expansion and contraction of the guard cells regulate the opening and closing of stoma. Stomata are necessary for exchange of gases (02 and CO 2) with the atmosphere. It allows gaseous exchange to occur during photosynthesis and respiration. During transpiration too, water vapour also escapes through stomata. During Fig. 2,12 A stoma (open and closed} and guard ceDs the process of photosynthesis, CO 2 is taken by the stomata from the atmosphere and O 2 is released as a byproduct. While during the respiration of plant, 02 is taken and CO 2 released via stomata. Photosynthesis occurs in day time (in the presence of light), but respiration occurs both in day and night time. . Cork cambium Cor\< The process of transpiration helfls the xylem tissue conduct (phellem) (phellagen) water and dissolved mineral salts by mass flow mechanism. -.J (b) Cork (or Phellem): Due to gradual thickness in diameter ..... of dicot stem and root, the outer peripheral cells form the .:.0 _.":.-. -::. -:.cork cells or phellem. These cells are arranged in radial rows. The cork cells have no intercellular spaces. These cells after Fig. 213 Co", or Phellum (IS.)
Tissues
53
.. ,
~~--~~---~~----~",,"
differentiation become dead. A fatty substance, suberin is deposited in the cell walls, due to which their walls become thickened. These cells are impermeable to water and gases. The cork cells also do not have protoplasm and nucleus and are filled with resin or tannin. Their function is to prevent loss of water from the internal tissues. After the formation of cork tissues, the cortical region (i.e., cortex) is not able to get water and nutrients, consequently its layers dry up and fall down. In onion bulb, the skin of onion becomes thick and water-proof due to deposition of suberin. 2. Complex Permanent Tissues • Xylem tracheUls, tracheae and xylem fibre are elongated and dead.
They are permanent tissues which contain more than one type of cells. All these cells coordinate to perform a common function. XYlem and Phloepl are examples of such complex tissues. Xylem and phloem are both conducting tissues and are known as vascular tissues: together both & of them constitute the vascular bundle. Vascular or conductive tissue is a distinctive feature of the complex plants, one that has made possible their survival in the terrestrial environment. The function of vascular bundles is to conduct water, mineral salts and soluble food materials to the different parts of the plant body. (i) Xylem: It is a complex tissue that forms a part of vascular bundle. It is mainly
Fog. 214
Xy~m
• Xylem cells conduct water and salls from roots to leaves.
54
concerned with the conduction of water and minerals and also provides mechanical support to the plant. As a conducting strand, xylem forms a continuous channel through the roots, stem, leaves, flowers and fruits. It consists of four different types of cells, both living and non-living. The four component of xylem are: (a) Tracheids (b) Vessels (tracheae) (c) Xylem parenchyma (d) Xylem fibre (sclerenchyma) (a) Tracheids: These cells are elongated with pointed chisel-like ends. Their walls are thick and lignified. They conduct water and is" '. dissolved substances from I the roots to the leaves. 1+-- Nucleus (b) Vessels (tracheae): These cells are also elongated I tube-like, and placed end to end. Their partition I walls are either perforated Cytoplasm or completely disappear I forming an elongated tube. The main function of these o vessels is the conduction (a) Tracheids (b) Vessels (c) Xylem parenchyma of water and minerals like Fig. 2.15 tracheids. (c) Xylem parenchyma: Their cells are living and thin or tluck due to the deposition oflignin. Their function is to store reserved food (starch) and help in the sidewise conduction of water upward mrough tracheids and vessels. (d) Xylem fibre (sclerenchyma): These are elongated and pointed at both me ends. Their walls are also thickened due to deposition of lignin. Except xylem parenchyma, the other three types of cells are dead and their walls are pitted. Function of xylem fibre is to giYe mechanical support to the xylem tissue. Tissues
.
Table 2.2 Differences between Tracheids and Vessels Vessels These arise from a number of cells.
2.
Tracheids These arise from a single cell. Their ends are tapering or oblique.
3.
The lumen is narrow.
The lumen is wide.
4.
Their walls are more thickened.
Their walls are less thickened.
S.No. I.
The ends are rounded or transverse.
(ii) Phloem: Phloem is another type of complex tissue. It
Companion cell
aids in the conduction of food such as amino acids and carbohydrates from the leaves down the stem, trunk, roots and other parts of the plant body. It is also called bast. It is composed of four types of cells (see figure): (a) Sieve tubes k '" ~ Parenchyma cell '.:n-.:;::.-, Nucleus of (b) Companion cells parenchyma cell (e) Phloem parenchyma i Sieve tube (d) Phloem fibres or bast-fibres , (a) Sieve tubes: The sieve tubes are composed of living, . Sieve plate . With sIeve pores slender and elongated tube-hke cells placed end to Fig, 2.16 T.S. of a phloem tissue end. The cell walls are thin and made up of cellulose. The transverse walls are obliquely placed and perforated by a number of pores called sieve plates. Due to these perforations between adjacent • Phloem conducts cells, dissolved food materials move from one cell to the other. The food food materials from leaves to different manufactured by leaves is transported to food storage organs (cortex) of parts of the plant. the plants. Their cells have a parietal layers of cytoplasm and are without nucleus. In the centre of each cell a large vacuole is present. (b) Companion cells: Long narrow, living, elongated cells are usually -'-'-' 0 . 0 Sieve plate attached with the lateral side of sieve tubes called companion I Sieve tube cell. Their lateral walls are thin and pitted and through these pits the cytoplasmic connection between sieve tubes and companion cells is established. The companion cells have t \1 I , Phloem cytoplasm and a large nucleus. Companion cells are supposed to help in the transport of food along with the sieve tubes. (c) Phloem parenchyma: These cells are like ordinary parenchyma II , Companion cell the cells are living. They are intermingled with sieve tube. Their function is to store food material and help in the transport of food. (el) Phloem fibres: These are sclerenchymatous cells. These '<:le>O cells are elongated, pointed, lignified and dead. They give Section of Phloem Fig. 2.17 T.S. of a phloem tissue mechanical support to the plant. They are used for making ropes and rough cloth.
00'--'001&tj
11-
~
Table 2.3 Comparison of Xylem and Phloem S.No. I. 2.
3.
Phloem It is a complex tissue. It is a complex tissue. Except xylem parenchyma, all other Except for phloem fibres, phloem xylem elements (sciereids, tracheae and cells are living. xylem fibres) are dead. Conducts water and minerals from Transports manufactured food from Xylem
fOOts
to leaves, etc.
leaves to storage organs and growing
parts of the plant body. Tissues
55
iUii@
Table 2.4 : Comparison of Meristematic and Permanent Tissues Meristematic tissues
S.No.
Permanent tissues
I.
Simple tissue.
Simple or complex tissue.
2.
Cells divide repeatedly.
Cells are derived from meristematic tissue and do not divide.
3.
All cells are alike (undifferentiated).
Cells are differentiated into vanous types.
4. 5.
Cells are isodiametric, i.e., all sides are Cells are of various shapes and sizes. equal. Intercellular spaces are lacking. Intercellular spaces are present.
6.
Cell walls are thin.
Cell walls may be thin or thick
7.
Vacuoles are not found
Vacuoles present in mature cells.
8.
Metabolically very active
Metabolically not active.
FORMATIVE ASSESSMENT FA 2.1: Match the Following Match the terms given in column I to their meaning in column II. Column I
Column II (i) Permanent tissue which makes the
(a) Collenchyma
plant hard and stiff (b) Chlorenchyma
(ii) Large air spaces or cavities present in
parenchyma tissues
to
give buoyancy
to the plants
(c) Aerenchyma (d)
(iii) Permanent
tissue that flexibility to the plant
Sclerenchyma
(iv) Chlorophyll-containing
provides
parenchyma
cells. (e)
Apical meristem
(v) Xylem and phloem
if) Lateral meristem
(vi) Increases length of the stems and the
roots (g) Complex tissues
(vii) Increases the girth of the stem or root
FA 2.2: Flow Chart-based Worksheet Fill in the blanks given below to complete the classification table. Classification of Plant Tissues
"
/
Meristematic Tissues
.--!----,. Apical
56
Intercalary
Permanent Tissues
FA 2.3: True or False State whether the following statements are True or False. 1. Meristematic tissue is the dividing tissue present in the growing regions of the plant. 2. Permanent tissues are derived from meristematic tissue once they lose the ability to divide. 3. Parenchyma tissue is a type of permanent tissue that consists of relatively unspecialised cells with thin cell walls. 4. Xylem transports food from leaves to other parts of the plant. 5. Stomata present in the epidermis of the leaf are necessary for the exchange of gases with the atmosphere. 6. Parenchyma are permanent live cells with thin cell walls. 7. Collenchymatous tissue consists of long and narrow dead cells with thick cell wall due to lignin.
FA 2.4: Concept-based Worksheet 'N is a permanent (plant) tissue with following characteristics: 1. It consists of relatively unspecalised cells with thin cell walls.
2. It is live, usually loosely packed. 3. It provides support to the plant and also stores food. Identify 'N and answer the following questions. (a) Write different types of 'A: tissue.
(b) Name the following: (i) Tissue that contains chlorophyll and performs photosynthesis (ii) Tissue with large air cavities that provide buoyancy to the plant (iii) Tissue that allows easy bending of various plant parts' without breaking (iv) Husk ofa coconut is made of which tissue?
•
FA 2.5: Diagram-based Worksheet Identify and name the following tissues. (a)
(b)
(c)
Tissues
57
FA 2.6 Group Discussion Divide the class in small groups. Discuss various plant tissues among each group. Now, on the basis of your discussion, discuss the following questions in your groups. 1. Where is meristematic tissue found in plants? 2. What are the various types of tissues in plants? 3. What is the difference between parenchyma and collenchyma tissues? 4. Write the difference between xylem and pWoem. 5. Name the different components of xylem and phloem.
Animal Tissues Breathing is one of the most vital activities of humans. When we breathe we can feel the movement of the chest. How do these body organs move? For this you have specialised cells in your body called muscles cells. The contraction and relaxation of these cells result in movement of your chest. During breathing you inhale 02. Where does this O 2 go? It goes to our lungs and then is transported to all the body cells through blood. Can you think why would cells need 02? You studied about mitochondria in the earlier chapter which is present in each and every cell of your body. They utilised O 2 and released energy in the form of ATP molecule. These ATP molecules provide energy to all work performed by our body cells. Blood is also a fluid connective tissue. It follows and carries various substances from one part of the body to the other. For example, it carries 02 and food to all cells. Blood also collects wastes from all parts of the body and carries them to the liver or kidneys for removal. Thus, muscles and blood, both are examples of tissues. There are four major types of tissues on the basis of their functions in multicellular animals, including man. (1) Epithelial tissue: Protective and covering tissue. (2) Muscular tissue: Contracting and relaxing tissues carryIng movements of vanous organs. (3) Connective tissue: Connecting, packing and supporting tissues. (4) Nervous tissue: Conducting impulses between central nervous system (brain and spinal cord) and other organs. These tissues are further differentiated as shown below: Animal Tissues
1. Epithelial
a. Squamous
2. Muscular
C.
(Flattened)
Columnar (Tall)
e. Glandular (Secretory)
a. Striated
3. Connective
b. Unstriated (Visceral
muscle) b. Cuboidal (Cubelike)
4. Nervous
c. Cardiac (Heart muscle)
d. Ciliated
a. Areolar
(i) Tendon
b.Adipose
(ii) Ugarnent
C.
Skeletal
(i) Cartilage
(il) Bone
(i) Blood
-----
.~ •.
58
d. Fluid
(ii) Lymph
Tissues
Epithelial Tissue or Epithelium (Epi
= upon, thelio = to grow)
It is the simplest tissue. This tissue covers the entire body externally as well as 'TTlally. It is the protective tissue of the animal body. The cells of the tissue are ~_t1y packed and form a continuous sheet. These are without intracellular spaces intracellular matrix. These rest upon a non-cellular layer known as basement mbrane which contains a special form of matrix protein, called collagen. ,ithelium covers most organs and cavities within the body. It also forms a barrier keep different body systems separate. The skin, the lining of mouth, the lining blood vessels, lungs, alveoli and kidney tubules are all made of epithelial tissue. _pithelial tissue may be simple, i.e., composed of a single layer or stratified, i.e., de up of several layers of cells. clions (i) The entire body is covered by epidermis (outermost layer of skin), which
protects the body from drying, injury and chemical effects and infections. (ii) Some epithelial cells secrete enzymes and hormones (e.g., glandular epithelium). (iii) Certain epithelial cells filter waste products from the blood such as urine, sweat and carbon dioxide. (iv) Epithelial cells absorb water and nutrients in the intestine (e.g., columnar epithelium). (v) Certain epithelial cells receive various stimuli, e.g., olfactory epithelium, epithelium of internal ear. (vi) Certain epithelial cells secrete mucous which lubricate the surface ofthe epithelium. Types of simple epithelial tissue: On the basis of shape and functions of cells, epithelial tissue is classified as follows: (a) Squamous epithelium (b) Cuboidal epithelium (c) Columnar epithelium (d) Ciliated epithelium (e) Glandular epithelium
I
(a) Squamous Epithelium
Nature: It is composed of a single layer of thin and flat, plate-like cells. They are united with each other to form a sheet. These cells form a sheet-like structure with mosaic appearance. Occurrence: It is found on the surface of skin, e.g., (epidermis), lining of body cavities like mouth, oesophagus, lining of blood and lymph vessels, ducts of glands, etc. Functions (i) It protects the underlying parts of the organ from injury, drying, entry of
germs, etc. (ii) These epithelia serve for easy exchange of materials by diffusion across them, for instance, in blood vessels and alveoli. Free surface
.~;; ~
Basement membrane
FIg. 2.18 Squamous epithelium
Tissues
Keratinised Stratified Squamous Epithelium
/
It is found in the skin and covers the external dry surface of the skin. It consists of several layers of cells. The cells of the deepest layer are cuboidal but those of the outer or surface layer vary in nature. In the outer few layers, the cells become hard and deposit a waterproof keratin or corny substance. This is called keratinisation or cornification. These layers consist of flat, dead cells and are referred as stratum corneum or horny layer (see Fig. 2.19).
Q~~~~~~~~~~-,Stratum spinosum c:~-- Stratum
basale
It is shed at intervals due to friction as small pieces. It forms the epidermis of the skin in terrestrial vertebrates. It prevents loss of water and mechanical injury.
F~219
Nucleus
Cytoplasm
• Cement
substance Fig. 2.20 Cuboidal epithehum
Columnar cell
Nucleus
Fig. 2.21 Columnar epithelium
Nucleus
Cilia
/
Basement membrane
..
F.g 222 C a ec columnar epithelium
60
I
(c) Columnar Epithelium
Nature: This epithelium consists of cells which are much longer than broad (i.e., pillar like). Nuclei are placed near the base at the same level. Often their free borders bear microvilli. Occurrence: It forms the lining of the alimentary canal from stomach to rectum, gall bladder, bronchioles of lungs, uterine tube and uterus. Functions: It helps in absorption of nutrients in stomach and intestine, and secretion of mucous from mucous secretory glands. called goblet glands.
Basement membrane
Columnar cell
(b) Cuboidal Epithelium
Nature: Its cells are cube-shaped, isodiametric and closely fitted together. They appear square-shaped in section and their free surface appears to be hexagonal. Occurrence: It is found in some parts of kidney tubules and ducts of salivary glands, thyroid gland, sweat gland and exocrine glands like pancreas. It also forms the ovaries and lines the germ-producing tubules of the testis, here, it is known as germinal epithelium. Functions: (i) It helps in absorption, secretion and excretion. (ii) It provides mechanical support.
• Basement membrane
I
I
(d) Ciliated Epithelium
Nature: It consists of columnar or cubical cells, has numerous, thin, delicate, hair like projections called cilia arising from the outer free surface of the cells. Occurrence: This is found in the trachea (wind pipe), bronchi (in lungs) and bronchioles (branches of wind pipe), kidney tubules, sperm ducts and fallopian tubes (oviducts). Functions: Cilia beat only in one direction and thus, expel mucus and dust, etc., from the lungs to the exterior. Similarly sperms and ova descend downward.
Issues
I
(e) Glandular Epithelium
Goblet cell
Some ofthe columnar epithelial cells of the epithelium change into glandular cells. Often a portion of the epithelial tissue folds inward and a multicellular gland is formed. This is glandular epithelium. It is found in the skin, lining of alimentary canal, pancreas, etc., secreting mucous, enzymes and hormones. Their main function is secretion.
\.
........
J
a~M~'
Remember Fig. 223 Glandular epithelium showing goblet cells in intestine
Epithelial tissue is found on the body surface and the covering of external and internal surface of organs. Epithelial cells are closely placed with each other and also placed on non-cellular basement membrane. Their function is protection, absorption, secretion and excretion.
illII , ----Columnar
,
Ciliated epithelium is found in trachea, bronchi and bronchioles, kidney tubules, sperm ducts and fallopian tube.
Mucous-secreting 'goblet' cell
Glandular epithelium is found in glands.
~
2. Muscle Tissues (or Muscular Tissues) The movement of internal organ such as heart and alimentary canal are caused by these tissues. Muscle cells are typically arranged in parallel arrangement allowing them to work together effectively. Muscles are responsible for all outward manifestations of life. The muscular tissue is formed of greatly elongated and ltighly contractile tissues and muscles cells which are called muscle fibres. These are placed together in the connective tissue to form bundles.
Functions (i) Movement of organ (ii) Locomotion (iii) Opening and closing of apertures (iv) Increasing and decreasing size of cavities or lumen of hollow organs
(v) Providing the proper shape of the body (vi) Beating of heart
Muscles are classified into (a) striated muscles (skeletal muscles), (b) unstriated muscles (smooth muscles) and (e) cardiac muscles.
(a) Striated Muscles These muscles are also known as striped, skeletal or voluntary muscles. Nature: These muscle fibres or cells show transverse dark and '.ght striations or bands due to which these are called striated or striped uscles. Since these muscles are attached to the bones in different parts f the body and hence are responsible for body movement, they are 'Ca1Ied skeletal muscles. These muscles work according to our will; they e also called \'oluntan muscles. Each striated muscle cell or fibre is long cylindrical, non-tapering, nbranched and multinucleated (having many nuclei), It consists of thin outer limiting membrane, called sarcolemma, which encloses coenocytic plasma, known as sarcoplasm. The nuclei are many d peripheral. In the sarcoplasm (cytoplasm) of the muscle cell are bedded a large number of contractile elements, called mYofibrils or rcostyles running parallel to one another lengthwise, :i...les
Sarcolemma Dark bands Nucleus
Myofibn
Sarcoplasm
Fig. 2.25 Striated muscle fibre
61
Occurrence: These are found in muscles of limbs (e.g., bicep and tricep' muscle of arms) in the form of bundles. These are also present in the abdominal wall in the form of sheets, diaphragm, tongue, pharynx and these are called yiscera striated muscles since these are found in internal (visceral) organs. Functions (i) These muscles are strong and powerful and undergo rapid contraction and
expansion. These muscles become tired due to continuous use for a long time and so they need rest. (ii) These muscles provide force for locomotion and all other voluntary movements of the body parts.
I
(b) Unstriated Muscles
Nature: These are also called smooth, yisceral or involuntary muscles. The cell structure is relatively simple. The cells or fibres are elongated and spindleshaped (pointed at both ends). These are held together by loose connective tissues. Each muscle cell is enclosed in a delicate and transparent plasma membrane. It consists of a long cigar-shaped nucleus in the centre of cytoplasm or sarcoplasm. The sarcoplasm contains fine longitudinal contractile thread called Nucleus Spindle shaped myofibrils. The fibres have no striations or bands across muscles hence, /\ ; ; : C l e ce~s :a ;& ~s-= are called smooth or unstriated muscles.
=
--=-.~
....
Occurrence: These are found in the wall of visceral organs except that of heart, that is why they are called visceral muscles:
- ==-===-
Fig, 2.26 Smooth muscle cells (fibres)
Thus, they occur in this wall of stomach, intestine and rectum, walls of arteries and veins, urinary and genital ducts, bronchioles, muscles of iris and ciliary body, etc.
Functions (i) The unstriated muscles are never under the control of our will, hence, they are also known as involuntary muscles. Movement of food in the alimentary canal or opening and closing of cavity are involuntary movements. (ii) These are independent of voluntary control except the ciliary muscle of the eye. (iii) They show slow and sustained contraction and relaxation (i.e., peristaltic movements which push the food onward) movements in the intestine.
I
(e) Cardiac Muscles Nature: These muscles resemble striated muscles but, functioning independendy of the conscious control of brain, these are involuntary like the smooth muscles. Cardiac muscles are composed of branched fibres, the branches join to form a network (see Fig. 2.27). Each fibre is surrounded by very thin sarcolemma and has cytoplasm (sarcoplasm) with longitudinal myofibrils and centrally located nucleus (i.e., each cell is uninucleated). The intracellular spaces of cardiac muscles are Space between fibres filled with abundant loose connective tissues richly supplied with blood filled with capillaries capillaries. and connectIVe tissue
Intercalated disk Myofibris
Fig. 2.27 Cardiac muscles
VK Biology IX
62
The fibres are joined end-to-end and are interconnected by oblique bridges. The ends of these fibres have zig-zagjunctions, called intercalated disc. These act as boosters for the wave of muscle contractions. These are regions of interdigitation of sarcolemmas of adjacent muscles or fibres (i.e., each fibre of cardiac muscles is formed due to joining of individual uninucleated muscle cells to one another in a linear arrangement). Occurrence: These muscles are present in the walls of heart. Tissues
Functions (i) Cardiac muscles contract and relax rhythmically throughout life without
showing any fatigue. (ii) Rhythmic contraction and relaxation of cardiac muscles maintain the flow of blood in the heart and blood vessels. Table 2.5 Comparison of Muscular Tissues S.No. J. 2.
Striated Muscles Voluntary or skeletal.
Unstriated Muscles
Cardiac Muscles
lnvoluntary, smooth or
Heart.
Sarcolemma present.
plain. Sarcolemma delicate and
Sarcolemma present.
transparent.
Myofibrils in sarcoplasm
Myofibrils indistinct and
distinct and cross striated.
not cross striated.
Myofibrils distinct and faintly striated.
Fibres or cells unbranched.
Unbranched.
Fibres branched.
5.
Nucleus, many in each
Single nueleus.
Single nueleus.
6.
cell. Intercalated discs absent.
Intercalated discs absent.
3.
4.
Intercalated discs present.
7.
Contraction rapid
Contraction slow and
Contraction moderate
powerful.
rhythmic.
and rhythmic.
3. Connective Tissue The name connective tissue is derived from its property to connect and bind different tissues or organs. It also provides the structural framework and mechanical support to the body. It also plays a role in body defence. tissue repair, fat storage, etc. It is composed of two basic components, namely, cells and their surrounding extracellular matrix. The cells are loosely arranged and lie embedded in the matrix, which consist of protein fibres, amorphous ground substance and tissue fluid. The matrix may be jelly like, fluid, dense Or rigid. The nature of matrix differs in concordance with the function of particular connective tissue. Types of connective tissue: In animals, connective tissue is of the following types: (a) Areolar (or loose) connective tissue; (e) Dense regular connective tissue; (e) Fluid connective tissue.
I
(b) Adipose tissue; (d) Skeletal tissue; Reticular fibre
Fibroblast
(a) Areolar (or Loose) Connective Tissue
Nature: It is also known as loose fibrous connective tissue or spongy fibrous tissue. It consists of a transparent jelly-like sticky matrix having different types of cells and fibres and lot of mucin. Its matrix consists of two types of fibres. (i) White collagen fibres that change into gelatin on boiling in
water. (ii) Yellow elastic fibres: Also scattered in matrix are several kinds of irregular cells (e.g., fibroblast). Some of these can engulf bacteria and prevent infection. Tissues
Collage'n fibre Mast cell FIg_ 2.28 Areolar connective tissue
63
Plasma
VK Biology IX
~~~----------------------_.--_
..... _--------_.~----..
Occurrence: Areolar tissues are the most typical types of connective tissues, having a very widespread distribution. These tissues are found between the skin and muscles, around blood vessels and nerves and in the bone marrow. Functions (i) It gives support to various organs and acts as a packing material between
various structures of the body. utritional exchanges occur through matrix. (ii) Injured tissues are repaired by the fibroblasts by producing collagen fibres. (iii) It defends the body against bacteria, microorganisms and other foreign bodies.
I
(b) Adipose Tissue (Fatty tissue)
Nature: It is a modified form of connective tissue. The fibres in adipose tissue are scanty. The matrix of adipose tissue is packed with large, spherical or oval fat cells or adipocqes. These store fat in the form of a large fat globule, which squeeze the cytoplasm to the periphery and nucleus to one side. Occurrence: The adipose tissues are present beneath the skin, around kidneys and in mesentry and bone marrow. Nucleus
Functions (i) It forms soft elastic pads between organs and parts. It maintains the
Fig. 2.29 Adipose tissue
I
kidney, its position and eye balls in the bony orbits and forms shockabsorbing cushions around both. (ii) It acts as a shock absorber, found beneath the skin, sole of foot and in the palm. (iii) It stores fat. (iv) It also gives shape to the body and hmbs. (v) It prevents the loss of body heat, thus, acts as an insulating blanket. Thus, it regulates the body temperature. (c) Dense Regular Connective Tissue
Nature: Dense regular connective tissue is a fibrous connective tissue. It is characterised by ordered and densely packed collection of fibres and cells. It is the principal component of tendons and hgaments. (i) Tendons: It is a dense, strong fibrous connective tissue with thick parallel
~tit:=::~E:
f
Fibroblasts Collagen fibres
Fig. 2.30 Dense regular connective tissue
64
bundles of collagen fibres (matrix). It has cord-like strong inelastic structure. It connects muscles to bones. It has great strength but limited flexibility. The collagen fibres are present in rows of fibroblast and are bounded by areolar connecting tissues. (ii) Ligaments: It is also a dense Tendon fibrous connective tissue. Its ground substance or matrix is Muscle densely crowded with yellow elastin fibres branched m different directions. A few elongated fIat cells (fibroblasts) lie scattered between the fibres. J-~~---- Bone The ligament connects bones --'-''-----'---- Ligament at the joints arid hold them in position-thus, enables us to Fig. 2.31 Attachment of tendons and ligaments move and rotate our neck, limbs, fingers, etc., comfortably. Tissues
Table 2.6 Comparison of Tendons and Ligaments S.No. 1.
Ligaments Tendons It is a thick, tough and non-elastic It is a strong but elastic bond of connective connective tissue.
tissue.
2.
It connects muscles to a bone.
It connects two bones.
3.
It is formed of wrute fibrous tissues.
4.
5.
It is formed of yellow elastic fibrous tissues. Fibres are white and formed of Fibres are yellow and formed of protein elastin. collagen protein. It helps in movement ofbone. It restricts or limits the movement ofbones.
c~hndrocyte ~
(d) Skeletal Tissue
The skeletal tissue forms a strong framework. It supports the body, protects vital organs and provides hard surface for the insertion of muscles. It occurs in two forms: Cartilage and bone.
Hyaline malnx
~
y~
/'
Fig. 232 Hyaline cartilage
(1) Cartilage
Nature: It is solid but semi-rigid and flexible connective tissue. The matrix of cartilage is called chondrion. It is tough, transparent and homogeneous, formed of a special glycoprotein chindromucoid. It is secreted by cartilage cells or condrocytes. These are enclosed in fluid filled spaces, called lacunae. The cartilage is bounded externally by white fibrous connective tissue perichondrium. The blood vessels are present in the perichondrium but not the matrix. The food and oxygen diffuse through matrix to reach the condrocytes. The cartilage increase in size by the addition of new layers of matrix below the perichondrium, by the division of chondrocytes (intestitial growth) and by the addition of chondroblasts from the perichondrial fibroblasts.
Perichondrium
ChondrrlaSI
I ~_1
Lacunae---.;J~:,'-~
.;;\~
.•
'
':"""''''. S Fig. 2.33 Section of cartilage
Occurrence: Cartilage is found in nose tips, ear pinna, ring of trachea (windpipe), end of long bones, lower ends of ribs, and epiglottis. Function: It provides support and flexibility to the vertebrate body parts. (2) Bone Nature: Bone is a solid, rigid and strong connective tissue. Its matrix is hard being formed of ossein. Matrix of bone is rich in phosphate, sulphate, carbonate and fluoride salts of calcium and magnesium. The bone cells are called osteocytes. These are stellate cells and each of them is enclosed in a small cavity, the lacuna. These are connected together by several fine and branched canaliculi. Fine processes of osteocytes extend through these conaliculi and are connected with the processes ofother osteocytes.
-=
~~~~~~ "" AlOOlL....
l~jJncanal
\'~~L Fig. 234 Compact bone
Haversian canal
Nucleus Bone lamellae
Protoplasm
Process
~ Lacunae
Canaliculi Osteoblast
Transverse section of bone
Single bone-secreting osteoblast
Fig. 235 SeclJon of bone (a part)
Tissues
65
-VK Biology
IX '
....
Functions (i) It forms the framework that supports the body. (ii) It protects vital body organs like brain, lungs, etc.
(iii) It anchors the muscles. (iv) It provides shape to the body.
Table 2.7 Difference between Cartilage and Bone Cartilage
S.No. I.
Matrix is composed ofa firm, but flexible Matrix is composed of tough inflexible material, called chondrion.
material, called ossein.
2.
Cartilage is surrounded by a firm sheath Bone is surrounded by a tough sheath, called perichondrium. called periosteum.
3.
Blood vessels absent.
4.
Cartilage cells (choridroucytes) lie singly Bone cells (osteocytes) lie in lacunae or in groups of two or four.
5.
I
Bone
Blood vessels present.
singly.
Chondrocytes are oval and devoid of Osteocytes are irregular and gIve off processes. branching processes.
(e) Fluid Connective Tissue
It is also called vascular tissue and is a special connective tissue that differs from a typical connective tissue in the following respects: (i) The matrix is in the form of a fluid and fibre free. (ii) Matrix is not secreted by the cells.
(iii) The cells lack power of division. Vascular tissue circulates in the body and helps in the transportation of materials from one part of the body to other part. It also plays an important role in the defence mechanism of the body.
Types of Vascular Tissue Vascular tissues are of two types: (a) Blood and (b) Lymph. (A) Blood Blood is a fluid connective tissue. It is salty in taste and slightly alkaline in nature. In human beings, it forms 7-8% ofthe body weight (about 5litres). Blood is a complex transport medium. It performs vital pick up and delivery services for the body. It contains two components: (I) Plasma and (2) Blood cells (corpuscles) (I) Plasma: It is a straw-coloured fluid, and makes up about 60% of the total blood volume or about 5.0% of the body weight. Plasma is a complex fluid and includes in it inorganic salts and organic compounds. Organic substances of plasma are soluble. Proteins like albumins (which maintain the pressure of blood); Globulin (some act as antibodies); and fibrinogen (blood clotting); and glucose, amino acids, lipids, vitamins, enzymes, hormones, etc. Supply blood to all cells of the body and waste materials (urea, uric acid) are transported to kidneys for excretion.
VK Biology IX
(2) Blood Cells: It is of three types: (i) Red Blood Cells (RBCs) or erythrocytes (ii) White Blood Cells (WBCs) or leucocytes (iii) Platelets (i) Red Blood Corpuscles (RBCs): The unique feature of RBCs is the presence of a red, oxygen-carrying pigment, the haemoglobin, in their cytoplasm. The shape and size of RBCs vary in different animals. The cells may be uninucleated or non-nucleated. In almost all the vertebrates, except mammals, these are nucleated, oval and biconvex. In mammals these are non-nucleated, bioconcave and circular. Actually, the nucleus is present in the RBCs of mammals initially but when these cells are finally differentiated and mature, the nucleus, mitochondria and endoplasmic reticululTI are degenerated. Such cells accommodate more haemoglobin for transportation of 02' (ii) White Blood Cells (WBCs): These are colourless, nucleated and motile (amoeboid) cells of blood, much larger than RBCs, but less in number. All leucocytes are capable of amoeboid movement. These are of two main kinds; phagocytes and immunocytes. Phagocytes are capable of phagocytosis and they carry out the function of body defence by engulfing bacteria and other foreign substances. These are of two types: (a) Granulocytes: They have irregular-shaped nuclei and cytoplasmic granules with specific staining properties. They include eosinophils, basophils and neutrophils. (b) Agranulocytes: These are nongranular leucocytes, having a roughly round or indented nucleus and clear cytoplasm. They include monocytes. They ultimately migrate to body tissue and transform into macrophages and histocytes, (c) Immunocytes: They produce antibodies and are involved in immune response. They include lymphocytes that contain central, spherical nucleus and a little cytoplasm with no granules and produce antibodies. (iii) Blood platelets or thrombocytes: These are minute, highly contractile, round or oval, biconvex discs with granular cytoplasm, but without nucleus. As is recently discovered, the platelets are fragments which form as buds and pinch off from certain large cells (megakaryocytes) in bone marrow. They help in the clotting of blood in the site of injury to a blood vessel, so as to prevent further loss of blood. Occurrence: It occurs in blood vessels called arteries, veins and capillaries that are connected together to form the circulatory system. The highly branching network of vessels enables blood to reach every part of the body. Functions: Blood is an important tissue since it performs many important functions in the body. (i) It transports oxygen from respiratory organs to various body tissues. (ii) It carries carbon dioxide from body tissues to respiratory surfaces like lungs,
skin, etc. (iii) Digested food absorbed from the intestine is carried to different parts of the body. (iv) It carries excretory wastes produced in the body to kidneys for elimination. (v) It maintains the body temperature.
67
(B) Lymph Nature: It is also a fluid connective tissue flowing in definite lymph vessels. Lymph is colourless since it has no red blood cells, but it contains more WBCs than the blood has. It also contains glucose, amino acids, vitamins, salts and urea. Functions (i) It transports the nutrients (02 and glucose) which may have filtered out of
the blood capillaries back into the heart to be recirculated in the body but has failed to return into various capillaries. (ii) The WBCs of the lymph are the same as those of blood and have the same function of defence and of assistance in tissue repair and healing. (iii) It brings carbon dioxide and nitrogenous wastes from tissue fluid to blood. Table 2.8 Comparison of Blood and Lymph Blood
S.No.
Lymph
1.
Red cells present.
These are absent.
2.
Amount of nutrients and 02
Amount of nutrients and O 2
comparatively more.
comparatively less.
3.
Amount of CO 2 and metabolic wastes less.
Amount of these wastes are much more.
4.
White cells fewer.
White cells more.
5.
Nutrophils most numerous.
Lymphocytes most numerous.
6.
Soluble proteins more than insoluble
Insoluble proteins more than soluble
proteins.
proteins.
4. Nervous Tissue Nature: A tissue which is specialised for receiving and transmitting messages in our body is nervous tissue. The brain, spinal cord and nerves are all formed of nervous tissues. The nervous tissue is composed of specialised cells or neurons, which receive the stimuli from within and outside the body and send impulses (signals) to various parts of the body. The signals or impulses travel from one neuron to the other. Dendrites
~'-~
Nucleus . , Myelin sheath
Axon
/
I
Structure of Neuron A neuron or nerve cell consists of three parts (Fig. 2.36): (a) Cell body or cyton is bounded by a thin cell membrane, enclosing the cytoplasm,
called neuroplasm. A large central nucleus is found in the neuroplasm. (b) Dendrons or dendrites are short processes arising from the cyton. They conduct impulses into the cyton from the receptor organs. (e) Axon is single, thick and large. It arises from the cyton and terminally it is branched. Axon is also known as nen'e fibre. Axons carry nerve impulses away from the cyton, i.e., to effector organs (muscles). Function Dendrons of the nerve cell receive impulses from receptor organs, carry to the cyton and axon transmits them away from the cyton to another neuron or effector organ.
Terminal branches
Fig. 2.36 ANeuron
68
Tissues
FORMATIVE ASSESSMENT FA 2.7 Diagram-based Worksheet Study the diagram and answer the questions that follow. A.
3
I. 2. 4. 5.
Complete the diagram by drawing the missing parts. Identify the parts numbered 1,2 and 3. What is the term given to the gap between two nerve cells? Name the part of the neuron from which the nerve impulse is transferred to the second neurons.
B. Given below are the pictures of different types of epithelial tissues. Mention the name of correct epithelial tissue under their respective pictures.
.
'
FA 2.8 Mapping-type Worksheet Complete the following map.
Tissues
69
FA 2.9: Match the following Match the terms given in column I to their meanings in column II. Column I (a)
Blood
(b) Involuntary movements
(c)
Column I (i) Smoothens bone surfaces at joints
Cartilage
(ii) Fluid connective tissue
(iii) Movement of food in alimentary
canal or contraction and relaxation of blood vessels (d) Cuboidal epithelium
(iv) Forms oesophagus and the lining
of the mouth (e)
Columnar epithelium
(j) Simple squamous epithelium
(v)
Forms the lining of kidney tubules and ducts of salivary glands
(vi) Forms
the Inner lining of the intestine
FA 2.10 True or False State whether the following statements are True or False. l. A neuron consists of a cell body with a nucleus and cytoplasm from which long
2. 3. 4. 5. 6. 7. 8.
thin hair-like parts arise. The movements of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements. The areolar connective tissue is found in the nose, ear, trachea and larynx. Bone is a connective tissue which forms the framework that supports the body. In the respiratory tract, the cuboidal epithelium tissue also has cilia, which are hair-like projections on the outer surfaces of epithelial cells. The skin lining of the mouth, lining of blood vessels, lung alveoli and kidney tubules are all made of connective tissue. Muscular tissue consists of striated, unstriated and cardiac tissues. The muscles of the heart showing rhythmic contraction and relaxation are called cardiac muscles.
FA 2.11: If I was A ... ? Worksheet Pretend that you are an animal tissue for the remaining questions. l. Name the different types of tissues found in you.
2. Name the tissue which is found on the surface of yOUT skin and is composed of a single layer of thin and flat, plate-like cells. 3. Where is cuboidal epithelium found in yOUT body? 4. Which ofyour connective tissues helps in forming the framework that supports the body? 5. What are the functions of voluntary and involuntary muscles in yOUT body? 6. Which of your tissues transmits stimulus very rapidly within the body? Name the parts composed of such tissues.
70
.,
Tissues
SUMMARY I Epithelial tissue covers the external and internal surfaces of the body and various I I I I I I
I I
I I I I I I I I I I I I
I
organs. Epidermis of skin is formed of stratified epithelium. Glands are formed of glandular epithelium secreting mucous and enzymes, etc. Goblet cells are glandular epithelial cells that secrete mucous. Areolar or loose connective tissue is formed of various types of cells, unbranched collagen and branched elastin fibres scattered in a large intercellular space or matrix. Cells are fibroblasts secreting fibres, macrophages or histiocytes engulfing bacteria, etc., mast cells secreting heparin, histamine and serotonin, adipose cells storing fat, etc. Adipose cells store fat in their vacuoles and also have fibres in between cells. Dense connective tissue forms ligaments and tendons. Tendons are formed of collagen fibres and in between them are fibroblasts. Tendons connect muscles to bones. Ligaments have collagen and elastin fibres and squeezed fibroblasts. They connect bone to bone. Striated muscle fibres have cross-striated myofilaments in sarcoplasm. Each fibre is multinucleated. Non-striated muscle fibres have no cross banded myofilaments. Each fibre has a single nucleus. Cardiac muscle fibre is uninucleated and branched. Myofilaments have faint cross striations. Sarcoplasm is the cytoplasm of muscle fibres. Sarcolemma is the limiting membrane of muscle fibre. Intercalated disc is the thick transverse band between two adjacent cardiac cells. Myofilaments are present in the muscle fibres in sarcoplasm. In striated muscle fibres thick and thin myofilaments are present. Cyton is the cell body of neuron or nerve cell. Dendrons or dendrites are short processes of cyton. Axon is a single long process of cyton. Synapse is the junction or union between the branches of two neurons. Tissue is a group of cells of common origin, having similar structure and function. Plant tissues are of two types: meristematic and permanent. 1. Meristematic tissues are present in growing regions of plants. Its cells continuously multiply so that the region grows in length and breadth. This tissue is of three types: (i) Apical meristem found at the apex of shoots and roots. Root tip is covered by root cap. (ii) Lateral meristem is found on lateral sides of stem and root, e.g., cork cambium and cambium of vascular bundles. (iii) Intercalary meristem is a part of apical meristem which separates off laterally from the apical meristem. 2. Permanent tissues arise from meristematic tissues, cells of which after maturity form permanent tissues. It is of two types: simple tissues and complex tissues. Simple tissues are of three types: (i) Parenchyma cells are living and cytoplasm is vacuolated and possess intercellular spaces, cell wall is thin. (ii) Collenchyma cells are living and contain chloroplasts. Hence, they are capable of
Tissues
71
synthesising starch and sugar. Being elastic, it gives tensile strengths to the stem. No intercellular spaces.
I
I
I I I
I I I I
I I
I
I I
I I I
I
72
(iii) Sclerenchyma fibres or cells are long, narrow and pointed. On maturity, protoplasm dries off. Sclereids or stone cells or grit cells are of irregular shape. Cells lumen is narrow and gives strong support to the stem. Protective tissues are epidermis of leaves possessing stomata for exchange of gases. Cork is found on the outermost side of stem. Its cells are dead. Complex tissues are xylem and phloem. Xylem forms the woody part of stem. Xylem and phloem forms the vascular bundle. Xylem is constituted by four types of cells (e.g., sclereids, tracheae and xylem fibre or sclerenchyma are dead and xylem parenchyma is living) and it conducts water and nutrients from soil through roots to the leaves. Phloem is also formed of 4 types of cells: sieve tubes, companion cells, phloem fibres and phloem parenchyma. Sieve tubes and companion cells transport manufactured food from leaves to other parts of plants. Phloem fibres and sieve tubes are dead. Animal tissues include epithelial, connective, muscular and nervous tissues. Epithelial tissue is found on the surface of the body and various organs, lining the cavities of tubular organs. Its cells are of various shapes and are held together with a small amount of intercellular substance, matrix. Epithelium is of two types: simple formed of a single layer of cells and stratified formed of a number of cell layers. Simple epithelial is squamous, cubOidal, columnar, glandular and ciliated. Stratified epithelium cells are arranged in layers, like epidermis of skin. Muscular tissue includes striped, unstriped and cardiac muscles. Their cells or fibres are long and nucleated. Striped muscle fibres or cells are multinucleated and show alternate dark and light bands, due to which they are called striped. Muscles of legs and hands are of striped type. Each muscle fibre contains a number of thin and thick myofilaments within sarcoplasm. Non-striped or visceral muscle fibres are also long, cylindrical and uninucleated. Each fibre also contains numerous lengthwise arranged myofilaments in sarcoplasm. These muscles are found in the walls of internal organs of the body. Cardiac muscle fibres or cells are branched and uninucleated. The sarcoplasm of these cells also contains myofilaments showing faint cross striations. Branch of a cell joins the branch of adjoining cell. At the junction of adjacent cell is present a transverse intercalated disc. In between adjacent cells are present intercellular spaces having loose connective tissue. It is found in heart due to which it contracts rhythmically. Connective tissue connects and anchors various organs of the body and gives support to the organs. It contains an abundant jelly-like intercellular medium (matrix), fibres (white and yellow) and various types of cells, e.g., fibroblasts, macrophages, mast cells, adipose cells and immunocytes. Connective tissues are areolar (loose), dense and adipose tissues. Tendons join muscles to bones and ligaments join bone to bone, and both are dense connective tissues. Adipose tissue cells store fat globules. Cytoplasm with nucleus is peripheral. Blood and lymph are fluid connective tissues. Lymph is colourless and has plasma minus red blood cells and certain proteins. Cartilages and bones are skeletal connective tissues. Nervous tissue is formed of neurons. A neuron has a cell body, the cyton, a few small branches of cyton, the dendrons or dendrites and a single long branch is called axon. Axon carries away impulses from cyton and transmits them to another, whereas dendrons receive impulses and transmit them to cyton. Tissues
FORMATIVE ASSESSMENT FOR PRACTICE FA 1. Wordplay A wordplay is one where you choose a word or name and use each letter in the name as the beginning of a word or line that says something about that person or topic. Example: As given in Chapter 1. Write the wordplay using the word below:
p-----------------------------
A
_
R
_
E
_
c
_
H
_
y-----------------------------
M
_
A
_
FA 2. Young Scientist To show how apical meristem increases length of the stem and the root You will need: Two glass jars, water, two onion bulbs, scissors and record book. • Take two glass jars, fill bOlh oflimn wilh waler. • Label one as ll' and another as 'B'. Now, take two onion bulbs and place them on tlze mouth ofjar. • Observe the growtlz of the roots in both tlze jan, i.e., ll' and 'B', for few days. • Measu1"f tlze length of roots on day 1, day 2 and day 3 in both tlze jars.
• Document your observation in your notebook.
L
• On day 4, take out the onion bulb fmmjm' 'B' and cut tlze Toot tips. • Now, again observe the gmwtlz of TOOts in botlz tlze jars, i.e., ll' and 'B'. • Afterfew days observe tlze changes and document Jour observations.
Jar A
Jar B
Results From the above observation, fiU in the blanks: Jar
Tissues
has longer roots because
_
73
FA 3. Multiple Choice Questions Select the right choice 1. Which of the following tissues has dead cells? (a) Parenchyma (b) Sclerenchyma (c) Collenchyma (d) Epithelial tissue 2. Girth of stem increases due to (a) apical meristem (b) lateral meristem (c) intercalary meristem (d) vertical meristem 3. A person met with an accident in which two long bones of hand were dislocated. Which among the following may be the possible reason? (a) Tendon break (b) Break of skeletal muscle (c) Ligament break (d) Areolar tissue break 4. While doing work and running, you move your organs like hands, legs, etc. Which among the following is correct? (a) Smooth muscles contract and pull the ligament to move the bones (b) Smooth muscles contract and pull the tendons to move the bones (c) Skeletal muscles contract and pull the ligament to move the bones (d) Skeletal muscles contract and pull the tendon to move the bones 5. Which muscles act involuntarily? (i) Striated muscles (ii) Smooth muscles (iii) Cardiac muscles (iv) Skeletal muscles (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) 6. Which is not a function of epidermis? (a) Protection from adverse condition (b) Caseous exchange (c) Conduction of water (d) Transpiration 7. Select the incorrect sentence (a) Blood has matrix containing proteins, salts and hormones (b) Two bones are connected with ligament (c) Tendons are non-fibrous tissue and fragile (d) Cartiage is a form of connective tissue 8. Cartilage is not found in (a) nose (b) ear (c) kidney (d) larynx 9. Bone matrix is rich in (a) fluoride and calcium (b) calcium and phosphorus (c) calcium and potassium (d) phosphorus and potassium 10. Contractile proteins are found in (a) bones (b) blood (c) muscles (d) cartilage 11. Nervous tissue is not found in (a) brain (b) spinal cord (d) nerves (c) tendons 12. Nerve cell does not contain (b) nerve endings (a) axon
,.
.. VK Biology ~ IX
--~
74
Tissues
(e) tendons (d) dendrites 13. The muscular tissue which function throughout the life continuously without fatigue is (a) skeletal muscle
(b) cardiac muscle
(e) smooth muscle (d) voluntary muscle 14. Which of the following cells is found in the cartilaginous tissue of the body? (a) Mast cells (b) Basophils (e) Osteocytes (d) Chondrocytes 15. The dead element present in the phloem is (a) companion cells (b) phloem fibres (e) phloem parenchyma (d) sieve tubes 16. Which of the following does not lose their nucleus at maturity? (a) Companion cells (b) Red blood cells (e) Vessel (d) Sieve tube cells 17. In desert plants, rate of water loss gets reduced due to the presence of (a) cuticle (b) stomata (e) lignin (d) suberin 18. A long tree has several branches. The tissue that helps in the side ways conductions of water in the branches is (a) collenchyma (b) xylem parenchyma (e) parench yma (d) xylem vessels 19. If the tip of sugarcane plant is removed from the field, even then it keeps on growing in length. It is due to the presence of (a) cambium (b) apical meristem (e) lateral meristem (d) intercalary meristem 20. A nail is inserted in the trunk of a tree at a height of 1 metre from the ground level. After 3 years, the nail will (a) move downwards (b) move upwards (e) remain at the same position (d) move sideways 21. Parenchyma cells are (a) relatively unspecified and thin walled (b) thick walled and specialized (c) lignified (d) none of these 22. Flexibility in plants is due to (a) collenchyma (b) sclerenchyma (e) parenchyma (d) chlorenchyma 23. Cork cells are made impervious to water and gases by the presence of (a) cellulose (b) lipids (e) suberin (d) lignin 24. Survival of plants in terrestrial environment has been made possible by the presence of (a) intercalary meristem (b) conducting tissue (e) apical meristem (d) parenchymatous tissue 25. Choose the wrong statement (a) The nature of matrix differs according to the function of the tissue. (b) Fats are stored below the skin and in between the internal organs (c) Epithelial tissues have intercellular spaces between them (d) Cells of striated muscles are multinucleate and unbranched
Tissues
75
• • • •
Apical, lateral and intercalary meristem Permanent tissues: Simple and complex tissues Parenchyma, collenchyma and sclerenchyma Phloem and xylem
FA 8. Oral Assessment Answer the following questions carefully. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. II. 12. 13. 14. 15.
What are the various types of tissues in plants? State the functions of parenchyma. What are the functions of xylem and phloem) Where is meristematic tissue found in plants? What is the difference between striated and non-striated muscles? Where is columnar epithelium found? Give the functions of sclerenchyma. What is the function of neuron? Write the names of cells found in the matrix of connective tissue. What are tracheids and vessels? What is connective tissue? Name the tissue associated with the conduction ohvater in plants. Name the elements found in phloem. What is the specific function of the cardiac muscle? Write two characteristics of a nerve cell.
FA 9. Paper Pen Test 1. Answer the following questions (a) Why are xylem and phloem called complex tissues? How are they different from one another? (b) Describe the structure and function of different types of epithelial tissues. (c) Why is epidermis important for the plants? (d) Give reasons for the following (i) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole. (ii) Intercellular spaces are absent in sclerenchymatous tissue. (iii) We get a crunchy and granular feeling when we chew pear fruit. (iv) Branches of a tree move and bend freely in high wind velocity. (v) It is different to pull out the husk of coconut. (e) Differentiate between scelerenchyma and parenchyma tissues.
2. Fill in the blanks (a) Cork cells possess
on their walls that makes them impervious to gases and
water. (b) have tabular cells with perforated walls and living in nature. (c) Bene possesses a hard matrix composed of and _
and are forms of complex tissues. (e) have guard cells. (j) Husk of coconut is made of tissue. (g) Xylem transports and from soil.
(d)
: - - - - i - 78
Tissues
L..-J
3. Multiple Choice Questions (i) Find out incorrect sentence (a) Parenchymatous tissues have intercellular spaces. (b) Collenchymatous tissues are irregularly thickened at corners. (e) Apical and intercalary meristems are permanent tissues. (d) Meristematic tissues, in its early stage, lack vacuoles. (ii) Which cell does not have perforated cell wall? (a) Trachieds (b) Companion cell (e) siseve cells (d) Vessels (iii) Intestine absorbs the digested food materials. What type of epithelial cells are responsible for that? (a) Stratified squamous epithelium (b) Columnar epithelium (e) Spindle fibres (d) Cuboidal epithelium (iv) Meristematic tissues in plants are (a) Localised and Permanent (b) not limited to certain regions (e) Localised and dividing cells (d) growing in volume (v) Fats are stored in human body as (a) cuboidal epithelium (b) adipose tissue (e) bones (d) cartilage (vi) Voluntary muscles are found in (a) Alimentary canal (b) Limbs (e) Iris of the eye (d) Bronchi of lungs (vii) Which of the following helps in repair of tissue and fills up the space inside the organ? (a) Tendon
(b) Adipose tissue
(e) Arelor
(d) Cartilage
4. Match the Following. Column II
Column I (a)
Filling of space inside the organs
(b) Striated muscle (c)
Adipose tissue
(d) Surface ofjoints (e)
Stratified squamous epithelium
(i) Skin (ii) Cartilage (iii) Alveolar tissue (iv) Subentaneous layer (v) Skeletal muscle
if) Permanent tissue
(vi) Cocalised thickening
if) Cellenchyma
(vii) Sclerechyma
5. True or False. (a) Epithelial tissue is protective tissue in animal body. (b) The lining ofblood vessels, long alveoli and kidney tubules are all made up ofepithelial tissue. (e) Epithelial cells have a lot of intercellular spaces. (d) Cells of cork are dead, suberised and compactly arranged. (e) Voluntary muscles control the movement of iris of eye.
Tissues
79
SUMMATlVE ASSESSMENT Textbook Questions 1. What is a tissue? Ans. Tissue is a group of similar cells which perform the same function and have a common Origin.
2. What is the utility of tissues in multicellular organisms? Ans. Tissues are made up of group of cells carrying a specialised function. Each specialised function is taken up by a different tissue. Since these cells ofa tissue carry out only a particular function, they do it very efficiently. For example, in human beings, muscle cells contract or relax to cause movement, nerve cells carry messages, and blood flows to transport gases, food, hormones and wastes materials and so on. Likewise, in plants, vascular tissues (xylem, phloem) conduct water and food from one part of the plant to other parts. So, multicellular organisms show division of labour through tissues. 3. Name the types of simple tissues. Ans. There are 3 types of simple tissues: (i) Parenchyma (ii) Collenchyma (iii) Sclerenchyma 4. Ans. 5. Ans. 6. Ans.
Where is apical meristem found? Apical meristem is found in shoot apex and root apex of plants. Which tissue makes up the husk of coconut? Sclerenchyma tissue. What are the constituents of phloem? Phloem is made up offour types of elements: (i) Sieve tubes (ii) Companion cells (iii) Phloem fibres (iv) PWoem parenchyma
7. Ans. 8. Ans.
Name the tissue responsible for movement in our body. Muscular tissue. What does a neuron look like? A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise called dendrites. Each neuron has a single long part called the axon. 9. Give three features of the cardiac muscle. Ans. (i) Cardiac muscles are involuntary. (ii) Cardiac muscle cells are cylindrical, branched and uninucleate. (iii) Cardiac muscles show rhythmic contraction and relaxation. 10. What are the functions of areolar tissue? Ans. Areolar tissue is a connective tissue. It fills the space inside tile organs, supports internal organs and helps in repair of tissues. 11. Define the term 'tissue'. Ans. A group of cells that are similar in structure and work together to achieve a particular function is called tissue.
80
Tissues
12. How many types of elements together make up the xylem tissue? Name them. Ans. Four types of elements make up the xylem tissue. They are: (i) Tracheids (ii) Vessels (iii) Xylem parenchyma. and (iv) Xylem fibres
13. How are simple tissues different from complex tissues in plants? Ans. A simple tissue is made up of only one type of cell whereas a complex tissue is made up of different types of cells. 14. Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall. Ans. The differences between cell walls of parenchyma, collenchyma and sclerenchyma are: Parenchyma Cell wall is primary.
Sclerenchyma
Collenchyma Cell wall is primary.
Cell wall is secondary.
Cell wall is thin and made up of Cell wall has irregular thickening Cell wall is uniformly thick due of cellulose. to deposition of lignin. very less cellulose. 15. What are the functions of the stomata? Ans. The important functions of the stomata are: (il Exchange of gases with atmosphere. (ii) Transpiration, i.e., loss of water in the form of water vapour.
16. Diagrammatically, show the difference in three types of muscle fibres. Ans. Intercalated disk Striations
Nucleus
Spindle-shaped
NUCleus~; ? S C l e c~lIs
~~~rm~Trf1iili~~~:5 ~ ~ - s::
Cardiac muscle fibre
....
- =====-
~
ITTlTl111IillJI
Smooth muscle fibre
Striated muscle fibre
17. What is the specific function of the cardiac muscle? Ans. Cardiac muscles occur in the heart and bring about the rhythmic contraction and relaxation of the heart throughout life. 18. Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body. Ans. Differences between striated, unstriated and cardiac muscles are as follows: Striated Muscle Structure
Location
Unstriated Muscle
Cardiac Muscle
The cells of striated muscles are long, cylindrical, unbranched
The cells of unstriated
The cells of cardiac
muscles are long with
muscles are cylindrical, branched and uninucleate.
and multinucleated.
uninucleate.
pointed ends and
These muscles are attached These muscles are present to the bones.
in the alimentary canal,
Cardiac muscles are present in the heart.
blood vessel iris of the eye, ureter and bronchi.
Tissues
81
19. Draw a labelled diagram of a neuron. Ans. Nucleus
Nodeof-__ ranvier
Axon
• ---Schwann cells
~
roc
E
2 c
I . Myelin sheath
""
o
:<
20. Name the following: (a) Tissue that forms inner lining of our mouth. (b) Tissue that connects muscle to bone in humans. (c) Tissue that transports food in plants. (tf) Tissue that stores fat in our body. (e) Connective tissue with a fluid matrix. if) Tissue present in the brain. Ans. (a) Simple squamous epithelium (b) Tendon (c) Phloem (d) Adipose tissue (e) Blood . if) Nervous tissue 21. Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle. Ans. Skin: Epithelial tissue (Squamous epithelium) Bark of tree: Cork (protective tissue) Bone: Skeletal tissue (connective tissue) Lining of kidney tubules: Cuboidal epithelial tissue Vascular bundle: Complex permanent tissue-xylem and phloem 22. Name the regions in which parenchyma tissue is present. Ans. Parenchyma is a simple permanent tissue present in the cortex and pith of stem and roots. It is also present in the mesophyll ofleaves. 23. What is the role of epidermis in plants? Ans. Epidermis is a protective tissue of plants. It provides protection to underlying tissues. Epidermis forms the outer covering of the entire plant surface. Epidermal cells on the aerial parts of the plant often secrete a waxy, water-resistant layer on their outer surface, which provides protection against loss of water, mechanical injury and invasion of parasitic fungi. In the roots, they help in the absorption of water. 24. How does the cork act as a protective tissue? Ans. The cork cells are dead and do not have any intercellular spaces. The cell walls of the cork cells are coated with suberin (a waxy substance). Suberin makes these cells impermeable to water and gases. Thus, it protects underlying tissues from desiccation (loss of water from plant body), infection and mechanical injury.
l:·----..u
82
HOTS (Higher Order Thinking Skills) 1. Animals of colder region and fishes of cold water have thicker layer of subcutaneous fat. Describe why? Ans. Fat-storing adipose tissue is found below the skin of animals of colder region and fishes of cold water. Storage of fats acts as an'insulator and prevents the body of animals in colder environment. 2. If a potted plant is covered with a glass jar, water vapours appear on the wall of glass jar? Explain why? :\ns. The potted plant release water in the form of water vapours from aerial parts of the plant. However, when a potted plant is placed inside a glass jar, water vapours remained inside and thus appears on the wall of the glass jar. 3. Water hyacinth floats on water surface. Explain. Ans. Water hyacinth is an aquatic plant in which large air cavities are present in parenchyma to give buoyancy to the plants to help them float. Such a parenchyma type is called aerenchyma. 4. Which structure protects the plant body against the invasion of parasites? :\ns. Epidermis, the enter protective layer of the plant body do not allow parasites to enter the body due to (i) secretion of waxy, water-resistant layer on their outer surface, this aids in protection against loss of water, mechanical injury and invasion of parasitic fungi. (ii) absence of intercellular spaces. (iii) thicker enter walls.
EXERCISES A. Very Short Answer Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. Tissues
(1 mark)
What is a tissue? What are the different types of plant tissues? Define simple tissues. What are tracheids and vessels? What is the function of sieve tubes and companion cells? Give the names of elements found in phloem. Which tissue of leaves has chloroplasts? Write the names of living tissues of plants. Write the names of animal tissues. Give the functions of epithelial tissues. What is the function of ciliated epithelium? Where is squamous epithelium found? What is connective tissue? What are the two main types of fibres of connective tissue;> Write the names of cells found in the matrix of connective tissue. How many types of muscles are found in animals? What is the function of neuron? Which of the muscle cells is uninucleated-smooth muscle or cardiac muscle? Which cells are thick at the corners-parenchyma or collenchyma? Name the tissue associated with the conduction of water in plants. 83
21. What is the position of meristematic tissue in plants? 22. What is the main difference between meristematic and permanent tissues?
B. Short Answer Questions
(2,3 marks)
1. Give two points of differences between striated and non-striated muscular tissues. 2. Differentiate between the following structures: (i) Trachied and vessel. (ii) Sieve tube and companion cell. (iii) Tendon and ligament. (iv) Collenchyma and sclerenchyma. (v) Areolar connective tissue and dense connective tissue. (vi) Parenchyma and collenchyma. 3. Write short notes on any four of the following: Collenchyma, sclerenchyma, glandular epithelium, connective tissue, cardiac muscle. 4. Write notes on: Sieve tubes and Trachieds. 5. Write two characteristics of nerve cell. 6. How many types of elements are present in the phloem? Write their functions. 7. How many types of elements are found in the xylem' Give their functions. 8. What is the specific function of cardiac muscle?
C. Long Answer Questions 1. 2. 3. 4.
(5 marks)
What is the function of erythrocytes (RBCs) and leucocytes (WBCs) in the human blood? What is tissue' Give a brief account of the chief types of tissues in plants. Describe structure and various functions of connective tissues. Give a brief account of chief types of the tissues in animals.
D. Practical-based Multiple Choice Questions 1. Neha offered a plate of mixed salad consisting of boiled potatoes grated cucumber slices of raw tomatoes, very small pieces of an apple and slice of guava to her 70 years old grand mother who refused to eat the salad because one of the ingredients of the salad contained lots of sclereids and made it hard for her to chew. Identify it. (a) Guava (b) Tomato (e) Cucumber (d) Apple 2. Cross section of a plant part shows the following cells. Identify them. (a) Sclerenchyma (b) Parenchyma (e) Collenchyma (d) T.S. of phloem tissue 3. Prerna of Class IX got a scolding from an external examiner, when she wrote the following statements as identifying features of cardiac muscles after observing the slide even under high magnification power in a compound microscope. Which of the statement was wrong? (a) Always present in heart (b) Presence of intercalated discs (e) Faint striations (d) Fewer mitochondria as compared to smooth muscles
l·----.-u
84
Tissues
4. The animal known as 'Ship of the desert' has hump made up of specific tissue which provides water at the time of scarcity. Identify the tissue. (a) Skeletal (b) Muscular (e) Nervous
(d) Adipose
5. A naughty student of class IX was pricking the live animals present in an aquarium in Kerala. His prick led to the movement of animals away from him. Only one of the animals did not feel the pain due to the absence of nerve cells. It was (a) hydra (b) starfish (e) crab
(d) ponges
6. Identify the incorrect pair from the following set. (a) Nervous tissue - Excitability and conductivity (b) Muscular tissue - Contractility (e) Cardiac muscles - Self excitatory (d) Smooth muscles - Self excitatory
7. Deepika Padukone, the famous Indian model was selected by Hemant Trivedi for a fashion show to display his summer collection. The show was held in Toronto, Canada in an open ground. As soon as Deepika reached the ramp, her body started shivering. This happened in order to (a) check the dispersion of body heat due to low temperature (b) increased flow of blood towards skin (e) increased heat production by muscles function
(d) increased heat production by muscles contraction
8. Rohit was aspiring to become Mr. India, so he joined a gym to build his body muscles. On day one, he exercised for about an hour continuously. Next day, he was in a bad state and found it difficult to move his legs and arms due to cramps. The cause was (a) cardiac muscles got tired due to constantly pumping 02 to the muskes (b) pyruvic acid was accumulated in all three types of muscles which led to pain (e) lactic acid was accumulated in striated muscles (d) ethanol was accumulated in striated muscles due to anaerobic respiration by the cells
9. During an entrance exam for Agriculture Research Services, the name of the tissue that gives rises to jute fibres was asked. Only one out of four candidates gave the correct answer. Identify the person. (a) Amit wrote that xylem fibres give rise to jute fibres (b) Ajita write that phloem fibres (e) Alpana sclereids (d) Rachit sieve tubes 10. You are shown two slides of plant tissues: parenchyma and sclerenchyma. You can identify the sclerenchyma by the (a) location of nucleus (b) thickness of cell wall (e) size of cells (d) position of vacuoles. 11. Label 'N and 'B' correctly in the following diagram. (a) A - Nucleus, B - Dendrite (b) A - Dendrite, B - Axon (e) A - Axon, B - Dendrite (d) A - Dendrite, B - Nucleus Tissues
/L<~<---A
I+---B 85
12. Four slides were observed under the microscope for spot test as shown below. The correct identification of the four spots is
[C]
[B]
[A]
[D]
(a)
A: onion peel
B: cheek cells
C: sclerenchyma
D: parenchyma
(b)
A: cheek cells
B: parenchyma
C: sclerenchyma
D: onion peel
(c)
A: parenchyma
B: cheek cells
C: onion peel
D: sclerenchyma
(d)
A: sclerenchyma
B: onion peel
C: parenchyma
D: cheek cells
13. Raj observed nerve cells under the microscope, and made the following sketch. The mistake in his drawing is the cyton with (a) cilia
(b) dendrites
(c) nudeus
(d) cytoplasm.
14. Observe the location and shape of the nuclei in the four drawings of the striated muscle fibres given below. The drawing that most resembles the slide of striated muscle fibre under the microscope is
[C]
[B]
[A]
(a) A
(b) B
(c) C
(d) D
[D]
Answers 1. (a)
2. (c)
3. (d)
4. (b)
5. (d)
6. (d)
7. (d)
8. (c)
9. (b)
10. (b)
11. (b)
12. (d)
13.(a)
14. (c)
III
,,~._---
86
Tissues
Chapter: Three
~M~[f@\Yl®M®mJ1t DmJ [P@@cQJ [ffi®~@lliJ [f~®~ FOOD RESOURCES: PLANTS Can you stay a single day without food? You may, but at the end of the day you will feel weak, giddy and might as well fall ill. Food is essential for all living beings. Food contains carbohydrates, fats, proteins, vitamins and minerals. We require these for our body growth and development, maintaining a good health and getting energy for work. Plants make their own food from air, water, sunlight and a green pigment present in them-chJorophyll, through a process called photosynthesis. That is why they are called autotrophs. However, animals including man cannot make their own food. They depend on plants and other animals for food. So they are called heterotrophs. The main source of man's food has been plants-cereals, pulses, vegetables, fruits, etc. are provided to man by plants. Products like milk, honey, eggs and meat are yielded from animals. Since time immemorial, man has been growing crops in the fields and rearing animals to obtaiu food and satisfy his hunger. Man has been continuously trying to produce more and more food of better and still better quality. ow with the growth of population it has become all the more important to increase its quantity and improve its quality. Our country is the most densely populated country of the world with a population of 1.04 billion people. According to estimates, India's population will stand at 1.34 billion by the year 2020. To support such a huge population we will require at least 240 million tonnes of grain production every year. Our scientists like Kurien and Swami nathan have put a lot of efforts to increase the food production of our country and make it self-sufficient and have also achieved some success in this regard. We have had the green revolution in late 1960s which contributed to increased food grain production, followed by the white revolution, which led to increased milk production, the blue revolution, the yellow revolution and the golden revolution. (see Table 3.1).
M.S. Swaminathan
• The founder of the green 1'evolution was M.S. Swa11linallzan.
"10 matter how much success we have had in this regard, but in this process
we have exploited the environment so much that it has led to its degradation. ow it has become important that we take care of the environment too, while we exploit its resources to satisfy our needs. Efforts are afoot in this regard also. Chemical fertilisers like urea have been replaced by organic manures. Use of pesticides like DDT, etc. which are known to affect the health ofmen and animals drastically, have been minimised and replaced by biological means. Organic farming is practised nowadays. Also, by increasing the production oHood, we cannot do away with the problem of hunger and malnutrition in our country, for, people should have money to have Improvement in Food Resources
87
:'i::;,=,=::;1;m)1-__":j
~mg;:.j an access to it. Hence people should be given employment and made self-sullici to earn their own living. Otherwise, grains would be simply stored in warehouse the businessmen. Table 3.1: Programmes for increasing food production in our country Food Resources
Programmes
Foodgrains Milk Pulses Oil Fish
Green Revolution
White Revolution Golden Revolution Yellow Revolution Blue Revolution
Crop Production
• Crops m'e agricultural plnnts g;rown in community
in large areas.
Agriculture is a profession of a large number of human population. Our economy is based on agriculture. Most of our people live in villages and are busy in agriculture. In the recent decades, agricultural production has increased manifold due to the development of new high yielding varieties of seeds and crop plants (Green revolution). Food grain production has been four times from 1960 to 2004 with just 25% increase in cultivable level area. Prof. M.S. Swaminathan was the architect of green revolution in India which occurred in late 1960s. He had been Director ofIA.R.i., and Director General ofI.C.AR. New Delhi and Director General of International Rice Research Institute, Manila. He also established M.S. Swami nathan Research Foundation in Chennai. He recognised the value of Mexican dwarf wheat variety and introduced that in India. Its yield was better than the early varieties. But it needed more irrigation and fertilisers. In green revolution, use of pesticides and weedicides were also increased. Swaminathan was called the fathe' of economic ecology by L.'\. Em'ironment programme. He got world Food Prize for the contribution he made against hunger in India. Table 3.2 Food Production in India in 1999 Food products 1. Cereals (wheat, rice)
Million tonnes
Animal products L
203.0
Million tonnes
~1eat
4.7
2. Pulses
16.1
2. Poultry meat
3. Vegetables
59.4
3. Fish
3.2
4. Roots and tubers
29.7
4. Milk
5. Fruits
38.6
5. Aquaculture
77.2 2.0
6. Edible oil Total
0.55
9.1 355.9
I
I
87 .65
The production of cereals is more in comparison to meat production. In India, vegetarian population is greater than that of non-vegetarians. Non-vegetarians also need cereals since they are not 100 per cent non-vegetarians. Cereal crops such as wheat, rice, maize, sorghum, etc., are seasonal crops. These are harvested in a season of about five months. Cereals were domesticated earlier than any other group of useful plants of today. Beside cereals, pulses and oil seeds were also discovered. • Cultivation is growing of crops from seeds.
.~,~
88
The wheat, rice, maize, sorghum, pulses (umd, arizaI', moong, etc.), oil seeds (mustard, soyabean, sunflower), vegetables and fruits are obtained from plant sources.
Improvement in Food Resources
Food giving plants are thus, as follows: (i) Cereals, e.g., wheat, rice, maize, jowar, bajra, etc. Wheat is mostly consumed in Punjab, Haryana, Uttar Pradesh and Madhya Pradesh. Rice eating people belong to the states of Bihar, West Bengal, Assam, Orissa and the southern states of India. Jowar and bajra are mostly used in Rajasthan and Gujarat. (ii) Pulses, e.g., arhar, gram, peanuts, 1IIoong. (iii) Oil seeds, e.g., mustard, cotton seeds, groundnuts, sunflower, soyabean, coconuts. (iv) Vegetables, e.g., potato, onion, brinjal, cabbage, carrot, cauliflower, lady's finger, gourd, etc. (v) Fruits, e.g., banana, mango, orange, apple, pineapple, lemon, peach, etc.
Table 3.3 Some Food Items Carbohydrates \. Wheat
\. Groundnuts
\.
2. Rice
2. Vegetable oil from
2. Eggs
Fats
Proteins
Milk
Minerals \. Green leafy vegetables 2. Beans
sunflower, soyabean, mustard, ground nuts.
3. Jowar 4. Bajra
3. Animal fat from meat 3. Meat and fish 4. Fish
3. Ragi 4. Dry fruit (almonds, etc.) sea weeds
5. Potato 6. Tubers and rhizomes
5. Bean 6. Pulses
7. Beet root
7. Grounclnuts
8. Vegetables
8. Peas
5. Liver 6. Eggs 7. Sea foods
Cereals (wheat, rice, maize, millets and sorghum) provide us carbohydrates, which is the main source of body energy. Calorific value of carbohydrate is 4.1 kcal. We get protein from pulses like gram, pea, black gram (urad), green gram (1Iloong) , pigeon pea (m'har) and lentil (nzassur). Calorific value of protein is 5.65 kcal. Proteins are used up in the body for making muscles etc. Thus, proteins are 'building materials' of the body. Oil seeds like soyabean, groundnut, sesame, castor, mustard, linseed and sunflower provide us with necessary fats. One gram of fat produces about 9.45 kcal of energy. Thus, fats provide more energy than carbohydrates and proteins. Spices, vegetables and fruits provide vitamins and minerals besides small amount of carbohydrate, protein and fat. Fodder crops are used as food for the cattles.
Crop Seasons The various types of crops (cereals, pulses, etc.) need different climatic conditions, temperature and photoperiods (duration of sunlight) for their growth and fruiting. On the basis of season, crops are of two types: kharif and rabi crops. Kharif Crops like rice, maize, jowar and bajra belong to cereals, and pulses like urad, arhar, and 1Iloong are grown in June after the first rains of the rainy season. Rainy season is from June to October. Rabi Crops are wheat (cereal) and pulses like gram and pea and oil producing plants like mustard and linseed are grown in November. Rabi season is from November to April. Improvement in Food Resources
89
VK Biology IX
----,.
There are certain crops which are grown between March and June and a: known as Zaid crops.
Improvement in Yields Agricultural practices can happen in three stages: 1. Crop variety improvement: This stage includes selecting ofseeds, hybridisati
and genetic engineering to get an improved variety of crops. 2. Crop production management: The second stage is nurturing of the cro plants through nutrients management, irrigation, cropping patterns, etc. 3. Crop protection management: The third and the final stage includ protection of the growing and harvested crops from damage. This is donte through proper storage, pest control and disease control.
activity 1 • Visit the llem-by agriculture fann in both seasons (kharif and mbi season) and find which CTOPS are sown. Ask the farmer which manure or fertiliser is being applied.
OW
Crop Variety Improvement Crop variety improvement is done for: 1. improving the productivity of crops. 2. improving the quality of yields. 3. developing crop varieties that are resistant to drought, water logging, heat and cold. 4. develop crop varieties that are resistant to diseases. This involves improvement in genetic makeup of a plant in relation to its economic use. This involves (i) selection of an improved variety of seed for planting. (ii) hybridisation of genetically dissimilar plants to produce a new kind, better in quality.
I Plant Breeding Crop improvement mostly involves plant breeding. The knowledge of genetics is essential for plant breeding. The aim of plant breeding is to produce a superior quality of plant and it should be adaptable to that environment, where it will be grown. The common methods of plant breeding are: 1. Selection
3. Induced mutations
2. Hybridisation.
4. Genetic engineering.
1. Selection
It is the process of choosing the plants with desirable characters. The plants with useful and desirable characters are chosen and maintained. The plants which are not useful and have undesirable characters are neglected and eliminated. The present day crop plants are being thus evolved due to continued selection of natural varieties of useful plants, over a long period of time_ The selection is continued with each generation during which some characters are lost naturally while others become stable. Such plants look totally different from their wild ancestors. This is the process by which wheat and maize plants were selected. In the past, man had
....
_-- VK Biology
IX
90
Improvement in Food Resources
selected a wild wheat having an inflorescence axis with intact floral stalks. Similarly maize variety having seeds embedded tightly were selected. These were continuously bred, and undesirable plants amongst them were discarded. Thus, the present day wheat and maize were produced. There are two methods of selection: (i) Mass selection, and (ii) Pure line selection. (i) Mass selection: It is the oldest and commonest method of breeding crop
plants. In this method, large number of plants having similar characters are selected and their seeds are mixed and grown together. Out of these plants which have desirable characters like height, disease resistance, growth rate, grain characters, etc., are selected and their seeds are again grown. From these plants, again undesirable plants are eliminated. This procedure is repeated till the desired plants and their seeds are obtained. This is the oldest and most common method of breeding crop plants. It is also known as the "German method of crop breeding". By self-pollination or self-fertilisation process, plants are multiplied and seeds are obtained. But it has a limited use for self pollinated plants. It is important for cross pollinated plants. (ii) Pure line selection: Pure line is a progeny of a single self-pollinated (selffertilised) individuals having same type of genetic characters. In this method also desirable plants are collected from a large different genetic type of population. These selected plants are self-pollinated for a few generations till a true breed or pure line progeny is obtained. Nter obtaining a true breed, these plants are multiplied on a commercial scale. Pure lines are specially important in the improvement of self pollinated crops. Most of the improved varieties of wheat, rice, pulses, oil seeds, etc., have been developed by this process. Concept of pure line and pure line selection was given by Wilhelm L. Johannsen (a Danish geneticist). 2_ Hybridisation It is a process in which two genetically dissimilar plants (two different varieties or between two different species ofsame genus or inter generic, i.e., between different genera) having desired characters are crossed or mated and brought together into one individual. This individual having known desired characters is called hybrid. It involves following steps: (i) Selection of parents: Plants selected for hybridisation should have desired
characters. One should be well adapted to that area and the other should have desired characters which are not found in the first chosen type. (ii) Emasculation: It is the removal of anthers or stamens or killing of pollen grains of a flower without damaging the female reproductive organs. Thus, self pollination and self-fertilisation is avoided. In bisexual plants, the male flowers or inflorescences are removed to prevent self pollination. In unisexual species, male plants are removed. (iii) Bagging: Nter emasculation, the flowers on inflorescence are enclosed in polythene bags or butter paper bags to prevent random cross pollination. (iv) Cross pollination: In crossing, mature, fertile and viable pollens from a desired male plant are collected and then placed or dusted on the stigma of the other female plant. Nter dusting, the female plant is bagged. Thus, natural fertilisation occurs which results in the formation of seeds. Mature seeds of F 1 generation are harvested, dried and stored. Later these seeds are grown, which give F I hybrids. Improvement in Food Resources
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VK Biology IX
Hybrid Vigour or Heterosis This F 1 hybrid is superior to the two genetically dissimilar parents. Ter heterosis was proposed by George H. Shull. Heterosis is measured in terms of siz growth rate, yield, etc. These cross pollinated species are heterozygous, i.e., differe from both the parents. Heterosis produces useful characters, like increased siz vigour, resistance to diseases and pests, and yield, etc. It is important in crops lik maize, wheat, sorghum, bajra, rice, cotton, sugar-beets, sunflower, tomato, brinj onion, etc. Hybrid vigour is lost by continuous inbreeding and hence parental line are to be maintained, for producing seeds. Hybrid vigour is the best maintained in vegetatively reproducing crops, like mango, guava, apple, chrysanthemum, dahlia. etc.
activity
2
• Students should visit nearby agricultuml fields and observe diffeTences of the same crop grown in different fields. Students may ask the fanners why there is diffeTence ofsame crop. Note down the factors for the difference. Advantages of H ybridisation (i) More vigorous and well adapted varieties can be produced. (ii) Hybrid possesses new genotypes.
(iii) Variety produced has superior characters. (iv) Hybrids mature early and need better fertilisers. (v) Hybrid crop yield will also be more. 3. Induced Mutations Sudden heritable changes are called mutations. Mutations could be natural (spontaneous) or artificial (induced). Induced mutations can be done by chemical and physical agents. These are of great importance in crop imp!·ovement. For induced mutations irradiations is commonly used. C0 60 or Cs' , are used for producing gamma rays. This facility exists in Nuclear Research Laboratory, IARI, New Delhi. Sharbati sonara wheat variety was produced by irradiation of Sonara 64 with gamma rays. Similarly Pusa lerma was produced from Lerma rojo 64. Wheat NP 836 is also produced by the same method. Improved varieties of rice, pea, cotton, etc., are also produced by induced mutations. 4. Genetic Engineering For crop improvement, manipulation of gene (Dl A) instead of complete chromosome set is done. In it a specific segment of DNA from living organisms is isolated and purified. DJ A sequence is broken off at two desired places to separate specific part of DNA. This part is later inserted into the DNA of the bacterial plasmid at a desired place. This DNA, thus obtained is called recombinant DNA. The method used is called genetic engineering. By this method one can add, or remove or repair part of genetic material and thus can change the qualities of an organism. Objectives of Varietal Improvement
..
-
--- VK Biology
"' -
(1) Improvement of yield: The aim is to develop high yielding varieties (HYV) of crops that will be economically beneficial. resistant, i.e., (2) Development of disease resistant crop. Crop should be db drought, water-logging, salinity, heat, cold, frost, etc., and also biotic resistant, i.e., disease resistant. Such a crop gives a good yield.
IX
92
Improvemex'
r
(3) Better quality of crop: As regards economic value, protein quality of pulses, oil quality in oil seeds and preservity of vegetables and fruits, are taken into consideration to estimate better quality of crops. (4) Photo-insensitivity and thermo-insensitivity of the crops: This helps in crossing the cultivation boundaries, e.g., high yielding wheat variety and MACS 2469 are able to tolerate high temperature, and are insensitive to light. (5) Early and uniform maturity: In some of the long duration crops, their ear" maturing varieties will be beneficial for harvesting the double and multiplecropping systems. It also reduces the cost of crop production. C niform maturit) makes the harvesting easy and reduces the loss of produce during harvesting. (6) Wider adaptability: Varieties which have wider adaptabilities should be developed. These varieties may be developed under different environmental conditions. Example is ICPH 8 hybrid pigeon pea which matures in a short time and is disease resistant against fusarium wilt and sterility mosaic. Its yield is also 30% to 40% more than the popular breed. It may be produced in drought conditions as well as high-moisture conditions. (7) Desirable agronomic traits: Desired agronomic traits give higher produce, such as high tillering, tall, profusely branching characters of fodder crops, and dwarf character of cereals. High yielding variety of wheat are Sonara 64, Hira, Moti, Kalyan sona and Sharbati sonara. HYV of Paddy are Pusa 205, IR 8, Padma and Jaya. High yielding varieties of cereals, fodder crops, oil seed crops, fruits, etc., can thus be developed by breeding and hybridization processes.
Crop Production Management Input and yield have a correlation. Better the input, better is the yield and for improving the input a systematic approach of management is required. This involves (i) supplying proper nutrients to the crops for its nurturing, (ii) ensuring that crops get water at the right stage during their growing season. (iii) use of different ways of growing crops to give the maximum output.
I
Nutrition Management
Plant Nutrition Plants need many inorganic and organic substances (nutrients) for their growth and reproduction. All these substances which plants take from outside constitute their food or nutrition. On the basis of their nutritional need, plants are classified into autotrophs and heterotrophs. Autotrophs are self-nourishing, they manufacture their own organic food and require only inorganic substances from outside. All green plants and photosynthetic bacteria are autotrophs. They obtain their nutrition mainly from soil in the form of inorganic ions. Heterotrophs need both organic and inorganic substances from outside. Saprophytes Putrefying bacteria like Bacillus and fungi [all fungi lack chlorophyll, (e.g., Mucor] and parasitic bacteria and fungi are heterotrophs. They do not manufacture their own food; they obtain it from other organisms. Plant nutrients are the mineral elements needed by the plants for their growth, development and maintenance. The nutrients taken by the plants from the soil are many more in number (13) than those taken from Improvement in Food Resources
93
VK Biology IX
water and air (3). Nutrients taken from air and water are more important, since they constitute about 97 to 99.5% of total plant tissue. Though, plants absorb a large number of elements from the environment but only the following sixteen elements are found to be essential nutrients for the plant nutrition: 1. Carbon 5. Phosphorus 9. Sulphur 13. Zinc Macronutrients
2. 6. 10. 14.
Oxygen Potassium Iron Copper
3. 7. 11. 15.
Hydrogen 4. Nitrogen Calcium 8. Magnesium Manganese 12. Boron Molybdenum 16. Chlorine
Plants require ten elements in relatively large amounts, carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulphur, calcium, magnesium and iron. These are called macronutrients. Out of these, last seven, P, K, N, S, Ca, Fe and Mg are present in the soil and are called mineral elements. Oxygen, hydrogen and carbon are provided to the plant by oxygen gas, water and carbon dioxide respectively. Micronutrients These are also essential for higher plants, but are required in very small amounts. Hence, these are called micronutrients or trace elements. These are copper, zinc, boron, molybdenum, chlorine, etc. Table 3.4 Sources of Plant Nutrients Nutrients
Air Water Oxygen and Hydrogen
Nitrogen, phosphorus, potassium, calcium,
carbon
sulphur, iron, magnesium, manganese, boron,
Soil
zinc, copper, molybdenum and chlorine. Carbon, hydrogen and oxygen are indispensible for plant growth. They constitute about 94 per cent of the total dry weight ofthe plant. Carbon is essen' for the synthesis of carbohydrates and fats. Oxygen and hydrogen are obtained fro water absorbed from the soil. Some oxygen is also absorbed from the atmosphere. • Hydrogen, Oxygen and Carbm fOTln 94% of the total plant tissue.
Nitrogen is absorbed from the soil in the form of nitrate ions (nitrates ofcalcium, potassium, ammonium and sodium). Its deficiency in plants causes chlorosis. Leaves become pale or yellow. Formation of red and purple patches or streaks in stems, leaf veins and petioles. Sulphur is absorbed by the plants as sulphate ions. Its deficiency also causes chlorosis in young leaves. Table 3,5 Differences between Macronutrients and Micronutrients S.No. I.
2.
• Mojo>' SOU1"CeS of plant nutrients are manures and fertilisers.
VK Biology IX
94
I
Macronutrients
Micronutrients
Found in plants in large quantities. Found in plants in traces. Concentration is more than 1 mg per g Concentration is less than 1 mg per g of dry weight of plant. dry weight of plant.
3.
Not toxic even if present
4.
quantity. quantity. Examples: Carbon, Hydrogen, Examples: Zinc, Manganese, Copper, Oxygen, Nitrogen, Calcium, Potassium, Chlorine, Boron, Molybdenum, etc. Phosphorus, Magnesium, Sulphur, Iron.
In
excess Toxic if present in more than required
Use of Manures and Fertilisers
Manures and fertilisers increase the fertility of the soil of crop fields. They also remove the deficiency of plant nutrients of the soil. They are used to increase the crop production. Improvement in Food Resources
1. Manures
Manures are natural fertilisers which are being used since ancient days. ~anures add small quantities of nutrients and large quantities of organic matter m the soil and make the soil soft for the better growth of root system and in turn plant growth. Capacity of holding water in the soil, etc., also increases. The microorganisms of the soil, beneficial to the soil and crop also get food. Manures are required in bulk quantities in comparison to chemical fertilisers. Large quantities of organic matter in clayey soils help in drainage of water and also avoid water logging. Types of Manures Manures are of three types: (I) Farm Yard Manure (2) Compost (3) Green Manure
• Manw-es are used in
bulk before sowing seeds (croP).
(1) Farm yard manure (FYM): It is the decomposed matter of cattle dung
(faecal matter), urine and litter, i.e., bedding material used in winter months at night under cattles. It also includes the leftover fodder in their manures. These materials are dumped daily in especially constructed pit away from the cattle shed. Action of microbes (e.g., bacteria, fungi, etc.) developed in this excreta, converts (decompose) it into manure, which is ready to spread in the crop fields. Farmyard manure is used in field before the sowing of crop, i.e., in October and in May/June in northern India. FYM is rich in potassium, phosphorus and nitrogen. It contains about 0.5 per cent potassium oxide, 0.15 per cent phosphorus pentoxide and 0.5 per cent nitrogen. (2) Compost: It includes farm and town refuge (e.g., vegetable matter, animal refuge such as excreta of domestic animals and stray animals, human faecal matter (sewage, etc.) stored in open fields beyond the limits of town (human population). Like FYM, it is also a biological process in which aerobic and anaerobic microorganisms decompose the town and city garbage and sewage waste into compost. Decomposition occurs between 3 to 6 months. Compost from town refuge contains about 1.4 per cent nitrogen, 1.0 percent phosphorus pentoxide and 1.4 per cent potassium oxide. While farm compost contains 0.5% nitrogen, 0.15% P205 and 0.5% K20. Method of preparing compost: For making compost, a trench or pit of 4 to 5 m long, 1.5 to 1.8 m broad and I to 1.8 m deep is dug. In it a layer of mixed refuse is spread. It should be about 30 cm in thickness. This is moistened with water and cattle dung or water and earth. Over it again mixed refuse is added which rises to a height of 45 to 60 cm above the ground level. ow the top is covered with a thin layer of earth. This is kept as such for 3 months, then it is taken out of the trench and formed into a conical heap. Again moisten it if necessary and cover it with earth. Leave it again for one or two months. Now the compost is ready to use in the fields. Town sewage is also recycled mechanically in activated sludge system in which solid wastes settle down at the bottom of the plant. It is called sludge. The upper clear water (sewage water) is being used in irrigation purposes and the organic waste is dried and used as manure. (3) Green manure: In green manure, generally leguminous as well as nonleguminous herbaceous plant seeds are sown in summers before the rainy season for about 6 to 8 weeks. These are sunhemp (Crotalaria juneea) , berseem (Egyptian clover-Trifolium alexandrium) , sesbania or dhaincha (Sesbania aeuleata) and guar or cluster bean (Cyamopsis tetragonoloba), cowpea (lobia), lentils (massur) , etc. These plants near the onset of monsoon are ploughed and buried in the field at a tender stage, i.e., at flowering stage. In the rainy rovement in Food Resources
• Composting is a biological process in which both aeTobie and anaerobic rmcroorganzsms decompose organic
"//Illtler in 3-6 months.
95
VK Biology IX
--'",
season these plants get decomposed with the help of decomposers. Then the new cereal crop is sown. Green manure adds nitrogen and organic matter in the soil. This adds to the fertility of the soil. It forms a protective soil cover and thus checks soil erosion and leaching. It increases the crop yield by 30 to 50 per cent. Green manure is used in this region by some large farmers. l:.artll\mrms in the soil especially after rains turn down the soil. They feed on soil containing organic matter and their casting is also rich in organic matter. They make the soil porous and increase the soil fertility. This type of composting is called \<,rmie 'llpostin;.,. • Ft1tilisers are c01nmercially prepared and richer in nutrients than manures.
• Fertilisers are used in small quantities in lhe field.
I 2. Fertilisers These are chemical fertilisers, manufactured commercially. They are richer in nitrogen, sulphur, phosphorus and potassium. They are better than the manures as regards nutrients and are thus used in small quantities. Fertiliser is a chemical compound, either inorganic or organic, containing one or more essential plant nutrients. Fertilisers, thus, increase the temporary fertility of soil and crop yield. In every crop, every time the crop is sown, these fertilisers are added to the soil. The various types offertilisers are: nitrogenous, phosphatic and complex. It is suggested to the farmers that before the application of these fertilisers, one should get the soil tested, if the soil needs nitrogen or phosphorus or potassium or all the three elements. Types of Fertilisers (i) Nitrogenous fertilisers: These are rich in nitrogen element. These are
urea, sodium nitrate, ammonium sulphate, ammonium nitrate and calcium ammonium nitrate. These are better for vegetative growth. (ii) Phosphatic fertilisers: These are rich in phosphorus. These are phosphates and superphosphates. Phosphatic fertilisers are good for better fruit production. (iii) Potassic fertilisers: These are rich in potassium, a micronutrient of plants. These are potassium chloride, potassium sulphate and potassium nitrate. (iv) Complex fertilisers: These contain two or three elements-nitrogen, phosphorous and potassium. These are urea, ammonium phosphate, nitro phosphate, and diammonium phosphate. Chemical fertilisers should be used judiciously and carefully. Heavy dose of nitrogenous fertilisers destroy the crop. Testing of soil before the application of fertilisers is essential. On the basis of the deficient element in the soil, fertiliser should be used. Overuse offertiJisers decreases the fertility ofthe soil. Heavy doses of chemical fertilisers get washed off through irrigation through drainage and enter rivers, lakes, streams, etc. and pollute them. This disturbs the natural ecosystem. Table 3.6 Comparison of Manure and Fertiliser S.No.
.......
VK Biology IX 96
Manure
Fertiliser
I.
It is a natural, organic decomposed It IS a commercially prepared animal waste (dung) and vegetative inorganic or organic compound. ,vaste.
2.
It contains small amounts ofnitrogen, It is rich in nitrogen, phosphorus and phosphorus and potassium. potassium.
3.
It increases the humus in the soil It does not add humus in the soil. due to great amount of the organic matter.
Improvement in food Resources
Manure is not nutrient specific. It Fertilisers are nutrient specific. contains all the nutrients in small i.e., contain nitrogen, phosphorus,
4.
amounts absorbed by the plants potassium. These are absorbed by the slowly from organic matter.
plant roots, being soluble in \vater.
Manure is cheap and is prepared by fertilisers are costly because they are
5.
every farmer in villages.
• Themost imporlant sources of biofeTtilisers is through Ihe use of legume-Rhizobium bacteria.
prepared in factories and also bear Government tax.
I
Manure is applied to the crop fields It is applied to the crop fields after in bulk before the sowing season. germination or at the time of sowing in a very minute amount.
6.
,'j Biofertilisers: These are biologically active products of bacteria, algae and
fungi. They enrich the soil nutrients especially nitrogen. These include nitrogen-fixing microorganisms. Biofertilisers are used for specific crops such as legumes (pulses), oil seeds and rice. They provide nitrogen to the crop plants. They are not used as an alternative to the chemical fertilisers, but play a supplementary role of providing nitrogen to the nitrogen deficient soil and crop plants. Some of the biofertilisers used in India are legume Rhizobium sJlllbiosis, Azolla algae (Anabaena sYlllbiosis), free-living bacteria (Awlobacler and Bacillus PO(\"III)"XI.l) living in the soil and fix atmospheric nitrogen. Cyanobacteria or blue-green algae are also nitrogen fixers and Mycorrhiza is in symbiotic association of fungi with roots of certain seed-bearing plants. Fungus absorbs nutrients from the soil and provides them to the host cells. Rhizobium has symbiotic relationship with roots of leguminous plants. Root nodules are formed due to fixation of atmospheric nitrogen by bacteria. They also leave large amounts of nitrogen in the soil which is useful for the next crop.
FORMATIVE ASSESSMENT F"
the
'l.ks
1. The crops which are grown in the rainy season are called crops. 2. The crops which are grown in the winter season are called _ crops. 3. Hybridisation of crops refers to crossing between genetically _ plants. 4. Wheat, gram, peas, mustard and linseed are crops. 5. required by plants include nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. 6. The process in which farm waste materials like livestock excreta, vegetable waste, sewage waste, straw eradicated weeds, etc. are decomposed in pits is known as - - - - 7. Fertilisers are washed away due to excessive irrigation and are not fully absorbed by the plants which leads to _ 8. is a farming system with minimal use or no use of chemicals as fertilisers, herbicides, pesticides, etc. and with a maximum input of organic manures, recycled farm wastes and bio-agents with healthy cropping system. 9. On the basis of the kind of biological material used, manure can be classified _ as
10. Abiotic streeses in crop production include
provement in Food Resources
and
97
4. "Vater also serves as a medium where enzymatic reactions occur. 5. Besides, the seed coat becomes soft after absorbing water and allows the developing embryo to come out of seed. 6. Too much water in the field inhibits aeration of the soil. 7. Irrigation after germination of seeds and some growth is essential for the proper growth of root systems and aerial branches (tillers). If the soil lacks moisture, the crop plants become pale and finally dry up. 8. Water is essential for the solubility of nutrient elements. The soil nutrients get dissolved in water and are absorbed by the plant's root systems. Chemical manures are also applied to the crop fields before irrigation. Mter application of fertilisers, crops are irrigated. 9. Except paddy crop, no crop needs standing water, which causes wilting of plants. 10. Water logging in the field causes salinity ofthe soil. It reduces the fertility of soil. Water needs for different crops is different. Therefore, it should be used judiciously.
I
Irrigational Requirements of Various Crops
Each crop needs a specific quantity of water at various stages of growth and fruiting. Some crops like paddy (rice) require more water. Plantation of paddy seedlings is done in water-filled fields. For their growth and development continuous irrigation is required. Paddy fields should be well watered. Therefore, this crop is sown In raIny season. Maize, jowar and bajra need very less water, though sown in rainy season starting from June. Wheat, gram, pea also require less water. These are winter season crops. Pulses also require less water. Type of crop: Timing of irrigation for various crops is also essential for a good yield. At the time of sowing, soil should contain enough moisture for germination. Irrigation ofa wheat seedling is required after it attains about 6 inches size. Wheat at the time of maturity needs no irrigation. If any how rainfall occurs at this time, the plants bend or fall in the field affecting the yield of crop. Nature of soil and their need of water: Various types of soils have different requirements of water. Sand,' soil is porous. Its particle size is relatively larger. Water easily percolates down and hence its water retention capability is very poor. Sandy soil, thus, needs frequent irrigation, so that plants may get enough water for their growth and fruiting. Example is Rajasthan where soil is sandy. There crops like jOWal~ bajra and maize are sown, which need very less water. They mostly depend on rains because facilities of irrigation are not proper. Clayey soil particles are relatively small and have very less permeability. It is capable of retaining water for a long time. Hence, frequency of irrigation is comparatively less and the crop plants get water for a long time. Thus, proper management of irrigation for various crops is essential for getting good crop yield.
I
Irrigation System
The common method ofirrigation in India are wells, tube wells, pumps, canals, tanks, river-valley system and river-lift systems. Irrigation is essential at various levels of crop production, such is sowing, tilling, flowering and fruiting. Some well known inigation systems are given as follows:
.-:.---
100
Improvement in Food Resources
1. Wells: Wells are bored at such places where there is enough ground water is enough. These are of two types: (i) Dug wells, and (ii) Tube wells. (i) Dug wells have their bottom surface below the ground water table. Water accumulates here from surroundings. Water is lifted for irrigation by mechanical means, Persian wheels operated by bullocks, horses and camels. (ii) Tube wells are dug very deep. Water is lifted from these wells by diesel or electricity run pun1ps.
F~
~
M,,}"
2. Tanks: These are small storage reservoirs. They store run-off water from the surrounding catchment areas. Small dams are constructed below the catchment areas to regulate the flow of water for agriculture. 3. Canal sy'tem' Canals get water mostly from large rivers. Doors are fitted at the mouth of canal joining the river to regulate the flow of water. A canal is distributed into branch canals, distributaries or fleld channels. These field channels irrigate the fields. For irrigation ofvat"ious fields, a rotation system is followed so that each and every farmer may irrigate his field. 4. River valley system: In the western ghat mountains of South India are present many steep and narrow riverine valleys. In this region, rainfall is very heavy during June to September and again in November and December. On the slopes and in the valleys, perennial crops [coconuts, supm"i (Areca nuts), coffee, rubber, tapioca, etc.] are cultivated. Rice crop is also grown in the bottom lands of tbe valleys. 5. River lift system: Water is lifted directly from the river for the irrigation of nearby fields. It is done due to inadequate flow of water in canal or due to insufficient release of water from the river reservoir. 6. Sprinkler irrigation system: It is introduced in canal irrigated areas of Haryana, Rajasthan and Madhya Pradesb. Drip irrigation system is in use in Maharasbtra, Karnataka, Andhra Pradesh, Odisba and Tamil Nadu. It is in practice with the help of Israel technical knowhow in Indian Agricultural Research Institute, ]\ew Delhi. They are also providing training to the people of various states. Here they are cultivating different varieties of roses, tomatoes, capsicum of yellow and red colour, gourd, etc.
ropping Patterns Mixed Cropping The practice of growing two or more crops multaneously at tbe same time is called mixed cropping ·ig. 3.2). Cropping activities go on all the year round in :ndia, if water is available for crops. In nortbern India, ere are two distinct seasons kharif Ouly to October) and hi (October to March). Crops grown between March and ne are called zaid. In some parts of the cou ntry, there FiQ 3.2 Mixed cropping
_.;;-..;,v. ;,e. ;,m. ;,en..;,l. ;,in..;,F,;.:oo..;,d. ;,R,;.:es;;;,ou;;;,r,;.:ce;;;,s
1..;,0. ;,.1 _iiii;n;;;;;liil
are no such distinct seasons. Crops are grown sale or mixed (mixed-cropping), or in a definite sequence (rotational cropping). The land may be occupied by one crop during one season (mono-cropping) or by two crops (double cropping) which may be grown in a year in sequence. More than two crops are also grown in a year . (multiple cropping). These are intensive cropping. Kharifcrops include rice, sorghum (kharif), bajra, maize, ragi, groundnut and cotton. Rabi crops are wheat, sorghum (rabi) gram and pea. Mixed cropping: Crop mixtures are widely grown, especially during kharif season. For example, Maize + uradbean; soyabean + pigeon pea (arhar); sorghum + pigeon pea, pigeon pea + mungbean, cotton + mungbean and groundnut + sunflower. During rabi season, especially in unirrigated area, wheat and barley, and wheat and gram, or wheat + barley + gram are the mixtures of grain crops. Brassica (mustard) and safflower are grown mixed with gram or even with wheat. Mixed cropping is an efficient way of using land. Breeders are developing plant types in pulses and oil seeds, with good compatibility with row crops. Choosing a mix crop: In mixed cropping, the following factors are to be kept in mind: 1. Nutritional demand should be different for both the crops. In case of wheat + gram, the latter provides nitrogen to the soil. 2. Water requirement of both the crops should be different. One needs more water than the other. 3. Duration of both the crops should be different, one of long duration and the other of short duration. 4. Root growth of both the crops should be different, one deep-rooted and the other not, so that they may get water and nutrients from different levels. 5. Size of the plants should also be different. If one crop is tall, the other should be dwarf. In this way, both the crops will get proper light, water and nutrients.
Advantages of Mixed Cropping 1. No crop failure: If one grows two crops at the same time in a field, having different requirements of nutrients and water, then harvesting of both the crops cannot be damaged or failed due to uncertain monsoon. One will definitely give a good yield. 2. Improves soil fertility: Usually cereal crops and leguminous crops are grown in mixed cropping. Leguminous crops provide nitrogen to the soil because their roots possess nitrogen fixing bacteria, while cereal crop depletes more nutrients. Thus, soil fertility is improved in mixed cropping. 3. Increase crop yield: Due to increased soil fertility, yield of both the crops is also increased. 4. Variety of produce is also increased due to mixed cropping. One gets fodder, pulses, vegetables and fruits in practising mixed cropping. It is beneficial to the family economonically and also to the farm animals. 5. Optimum utilisation of the field also takes place. 6. Minimize pest damage to the crops: In mixed cropping, one crop may be prone to a particular type of pest, weed or insect. But the other may not be susceptible to that pest. Thus, in mixed cropping chances of infestations are reduced. ow there is a need of increasing productivity per unit area and time. Thus, traditional mixed cropping has been retailored and system of intercropping has been introduced. 102
Improvement in Food Resources
I Intercropping
I .
It is different from the mixed cropping pattern, but here also two or more crops are grown together. Two or more crops are grown in the field in definite separate rows (Fig. 3.3). The combination of crops is like that of mixed cropping. Here row pattern of crops is definite, with one row of main crop, one, two or three rows of intercrops are grown (I : I; I : 2; I : 3 or I : 4). In intercropping, with wide-rowed slow-growing crops, companion crops may be grown in rows. In case of plantation crops, intercropping with pulses and fodder crops is common. Chillies are rotated withjowar, whereas onion, coriander, turmeric and ginger are grown as mixed crops with other seasonal crops.
7
...
........
,
~
Fig. 3.3 Inlercropping pattern
Table 3.7 Comparison between Mixed Cropping and Intercropping S.No. ' Mixed cropping Intercropping I. I It minimizes the risk of failure of Increases productivity per unit area of both the crops. the field. 2. Seeds of both the crops are mixed Seeds of two crops are not mixed. before sowing. 3. 4.
5. 6. 7.
I
Fertiliser to individual crop cannot Fertiliser can be applied according to the need of crops sown in rows.
be applied. No definite pattern of crop rows.
There is a definite pattern of rows of crops. Use of pesticides for pest control to Use of pesticide to an individual crop an individual crop is not possible. is possible. Harvesting of both crops separately Harvesting of both crops at different is not possible. times is possible. Marketing and consumption of both Marketing and consumption of the crops can be done at a time. crops can be done independently.
Fig. 3.4 InlercroDping of grOlmdnulsunnower
Multiple Cropping
Multiple cropping is getting more than two crops in a year in the same field. These intensive croppings (mixed cropping, intercropping and multiple cropping) may be done either in sequence or even there may be relay cropping-one crop undersown in a standing crop. Multiple cropping helps in the improvement of soil fertility. In mixed cropping, better crops having fertility in short duration are to be selected. This practice saves the time and labour of the farmers, cotton crop and groundnut crop are grown at the same time. Proper irrigation is also required in multiple cropping. Future of cropping pattern: With the increase in population, the irrigated area is incr!,asing and with advances in agricultural science, most of the extensive cropping patterns are giving way to intensive cropping. The development in minor irrigation works has especially provided the farmers with opportunities to crop their land all the year round with high-yielding varieties. This intensive cropping will require an easy and ready availability of balanced fertilisers and plant protection chemicals. There should be an appropriate price policy for inputs and agricultural produce. In India the size of the land holdings will diminish further in future due to population increase. Hence, the country has to produce enough for its people without deteriorating the quality of the environment. provemenl in Food Resources
103
1i'1:ffi11ti1J 'J 11'l"I~
Crop Rotation
F19 35 Crop
I
Crops are grown in a definite sequence in a year, such as cereal (wheat, barley) crop, and legume (pulse) crop alternately. Roots of the leguminous plants possess nodules in which nitrogen-fixing bacteria Rhizobiulll lives. They fix the atmospheric nitrogen and thus, maintain the soil fertility. It increases the crop yield and also helps to control diseases. Nitrogen is essential for the plant growth. Hence, the leguminous crops are sown in the field every year. This practice of growing two different crops in a field in a year in succession is very common among Indian farmers. For example, pulses, beans and groundnuts are alternately grown between wheat, maize, bajra crops. Peas and grams are grown along with wheat in the same season. Alier harvesting peas and grams, maize or bajra are sown. Pea and gram crop enrich the soil nitrogen. This agricultural practice helps in more yield of dle crops. Nitrogenous fertilisers are thus, less used.
-
Rotation of Crops 1. Rabi wheat is followed by crops such as maize, jowar, bajra, cotton and arhar.
Sometimes, some of the green manure crops such as sanai, 1IZoong, guaT, lobia are sown immediately after kharif to enrich the soil. Gram, linseed, barley and mustard are also included in rotations. 2. Maize (kharif crop) is a short duration crop. It is rotated with wheat, potato, barley, etc., in a one year rotation. In two years rotation, it is grown in rotation with cotton and sugarcane. 3. Groundnut (kharifcrop) is grown year after year. In certain places, it is rotated· with wheat,jowar, bajra, gram, paddy and cotton. Groundnut in certain places is grown mixed with jowar and bajra. Table 3.8 Three Types of Crop Rot"tion on the b<.sis " uration Types of crop rotation l. One year rotation
Crops in Rotation I. Maize (khari!) - Wheat (rabi). 2. Maize - mustard. 3. Rice - wheat.
2. Two years rotation
1. Maize - mustard - sugarcane - 11lelhi (Fenugreek). 2. Maize - potato - sugarcane - peas. 3. Rice - pea - rice - gram.
3. Three years rotation
1. Rice - wheat - mustard - muong - sugarcane - berseem.
2. Cotton - oat - sugarcane - pea - maize - wheat. I 3. Maize - potato - sugarcane - green manure.
Selection of Crops for Rotation For selecting the crops for rotation, the following points are
to
be considered:
1. Availability of soil moisture: It may be through rain, or through irrigation. For example: Rice is an ideal crop for areas likely to be flooded heavily by rains or by seasonally flowing river water. Wheat is grown in rabi season when the amount of rainfall is low, and it is necessary to irrigate the crop for getting a good yield. Dwarfvarieties of wheat need more water (irrigation) than the tall varieties. Barley is similar to wheat but it can withstand more draught because
._-
....,'oJ.,
104
Improvement in Food Resources
of its deeper and well-proliferated root system. Maize is very sensitive to excess water. Submergence of soil for 3 to 4 days during vegetative or flowering period can reduce the yield up to 50 per cent. Millets (sorghum, etc.) are the hardest among cereals. They are grown in rain fed conditions. Crop should be irrigated at least at the critical stages to maintain optimum moisture in the root zone during dry spells. Pulses are also grown under rainfed conditions and rarely receive irrigation. Oil seeds like groundnut, sesamum and niger (kharif crop), and samowel~ mustard, castor and linseed (rabi crop) are generally grown in rainfed conditions. Kharif seeds need one or two irrigations but rabi seeds require more irrigations during the growth period, cotton also needs less irrigation. _ Nutrient status oflhe soil: Crops of the same family should not be repeatedly grown in the same field year after year. It reduces some particular soil nutrients, thus depleting the soil fertility. This will also encourage the build up of diseases and insect pests. ~ v..i1abi.. nputs: Inputs are fertiliser and manures pesticides, implements and manpower, etc. More than twO crops should be grown in a year in a particular field. It will not deplete the soil nutrient, instead will add some nutrients to the soil. High input crops like sugarcane, potato, maize, wheat and rice may be grown before low input crop. This will maintain the fertility of the land. 4. Crops of short and long duration should be selected. 5. Marketing of produce: Farmer of the nearby town should grow seasonal flower and early vegetable for getting a good price of their product. Old traditional farming is less productive. Processinv 0 lrod"ce is more beneficial than the traditional marketing of produce. Assessment of Crop Rotation Selection of crops for rotation can be determined by comparing the productivity of crops, which use similar resources (fertilisers, manures and water) and give similar produce. For example, if we grow only cereals like wheat and rice or only pulses like umd, bean, aT/wI", lIloong and gram (chick pea), and use same inputs like fertilisers, water, pesticides, etc., the assessment can be done on the basis of the total produce and the amount of used inputs. But, if crop rotation system is followed, different crops are grown in the same field in a year, then the assessment will be different. It will be as follows: Cropping index: It is represented in percentage. Cropping index
=
Number of crops Number of years
x 100
Monetary input and output relationship: Efficiency of crop rotation described as an output per unit of input. Efficiency
IS
Output in terms of money
=
Input in terms of money
Cost-benefit ratio: Return per rupee invested =
Gross return fl.. Test cost 0 cu tlvauon
Net returns: The monetary difference of input and output value is expressed as: Net returns provement in Food Resources
=
Monetary gross return - Total cost of cultivation. 105
~!.r-,'"
Advantages of Crop Rotation 1. It improve the fertility of the soil. In crop rotation, cereals like wheat, maize, bajra, jowar are alternately grown with legume crops (pulses, peas, grams, beans, groundnuts, etc.), non-leguminous crops alternate with leguminous crops in the same field. Cereal crops utilise soil nitrogen for their growth, making the soil nitrogen deficient. When leguminous crops are sown in the same field they enrich the soil with nitrogen by fixing atmospheric nitrogen. Thus, the deficient soil from nitrogen again becomes enriched with nitrogen. This cycle goes on. This increase the productivity of the crop. 2. Productivity of foodgrains thus increases. 3. Saving of nitrogenous fertilisers, because nitrogen is provided by the leguminous crops. 4. It also helps in controlling weeds and pests.
Crop Protection • Animals, especinlly i'nsects, that cause
damage to crops are called pests.
Fields are infested with a variety of organisms that destroy the crops and cause great economic loss. These are called pests. They include weeds, microbes, fungi, insects, rodents, etc. Crops have to be protected from pests by using pesticides and herbicides. Crops also need to be saved from diseases by treating them with medicines. Even after harvesting, the seeds need to be stored properly and protected from damage. Crop protection deals with all this. Crop protection is a technique of protecting and growing crops and preserving agricultural products from natural enemies like insects and weeds, etc. A number of animals are attracted towards crop plants for food, shelter and breeding and cause harm to them. These animals are called pests. Pests are destructive organisms causing great harm to the standing crop in the field and also in storage. These pests are insects, mites, nematodes, rodents, birds, bacteria, viruses and fungi. The association of pests to the crops, plants, etc., is very intimate. It is not possible to eliminate these enemies completely, but we can minimise their effect to a greater extent by using pesticides (biocides). Crop protection is also called pest control. Pests cause direct damage to the plants.
• The chemicals which
au used to kill insects are called insecticides.
Loss offoodgrains due to pests is about 30 per cent throughout the world. In India, the damage to the crop yield due to pests and diseases is about 20 per cent. Insects destroy annually about 15 per cent ofthe food produced in India. Pesticides used to control or eliminate the pests include insecticide for killing insects, weedicides for eliminating the weeds and fungicides for killing the fungi. Pesticides are either sprayed on crop plants or used for treating seeds and soil. These pesticides on the other hand cause pollution of air and water if used in excess. It is easier and more effective to prevent a pest invasion by suitable preventive measures than to cure it, when it has attacked on the crop. The preventive measures against the pests are: (i) Use of resistant varieties of crop plants. (ii) Treatment of plants with a chemical, capable of protecting them from attacks. (iii) Control of parasites on seed and in soil before planting. (iv) Treatment of vectors of infection. (v) Control by altering agricultural practices, viz., crop rotation, deep ploughing,
changing cultivation seasons, etc. These are curative methods. (vi) Biological control of the pests by organisms is dangerous to the concerned pest. Such organisms are called parasites. ..... /.--......,
.
"
106
Improvemenl in Food Resources
Warm and humid climate is supposed to be more favourable for infestation of insect pests. For example, maize, jowar, bajra, cotton, etc. are grown before the rainy season in June and hence are more prone to insect pests and diseases than the wheat, gram, pea, etc.
1. Insect Pest Control A number of insects are serious pests of crop plants. They do harm the plants at all stages, all parts and products of plants. They cut roots, stems and leaves; suck cell sap from various parts of plants and bore into stem and fruits. They cause heavy economic loss to the farmers. Insects causing direct loss to plant are:
~~Q Sugarcane stem-borer
Sugarcane top-borer
.---
I Gundhi bug
Mustard aphid
Painted bug
Pyrilla (sugarcane leaf hopper)
Fig, 3.6 A few common Insect pests of crop plants
(1) Leaf eaters (defoliators): These insects possess biting and chewing type of mouth parts. They sometimes cause serious damage to the crop, e.g., grasshoppers, locusts, beetles, weevils and larval stages (caterpillars) or butterflies and moths. (2) Leaf miners: They live in between the upper and lower epidermis of leaves and eat the green parts of leaves, e.g., citrus leaf miner. (3) Leaf rollers: Caterpillars feed upon the leaves and roll up the leaves. These leaves later shrivel and fall off, e.g., cotton leaf roller. (4) Stem and root borers: Caterpillars of some insect pests bore the stems and roots of various crop plants and cause serious damages. They cause stunted growth and infested plants also dry up, e.g., rice stem borers and sugarcane borers. (5) Sap suckers: Some insect pests have piercing and sucking type of mouth parts. They suck the juice of plants. The extraction of sap or juice of plants cause severe damage to plants. Leaves become brown and fall. off, e.g., rice gundhi bug, mustard aphids, etc. (6) Bark and wood feeders: Beetles and weevils make tunnels in the bark and wood of trees and shrubs, e.g., bark eating caterpillar and termites. (7) Fruitdestroyers: They attack fruits, making them unfit for human consumption and seed purposes, e.g., fruit flies attack fruits of cucumbers, mango, guava, etc. (8) Seed feeders (storage insects): Certain insects like rice weevil, rice and flour moth, potato tuber moth, etc., damage the stored grains, etc. rovement in Food Resources
107
Insects causing indirect losses to plants: Most aphids and leaf-hoppers secrete honey dew on their host leaves, It causes the development of sooty moulds which checks the growth and development of plants, Blight, mould and wilt diseases are caused by fungus, bacteria and virus, These diseases are transmitted by sap sucking insects, Viral diseases of potato, tobacco, peach, etc., are transmitted by leafhoppers, aphids, etc. Control of Various Insect Pests (i) Control of root cutting types of insects is done by mixing insecticides in soil,
e.g" chlorop\Tiphos, (ii) Control of leaf and stem cutting and boring type of insects is done by spraying
or dusting the contact insecticides. These penetrate the exoskeleton of insects and kill them, e,g" lindane, thiodon and malathion. (iii) Control of sap-SUCking insects (e,g., aphids) is done by spraying of dimethoate, metasystox, etc. These are systemic insecticides, absorbed into the' tissues of plants, and when an insect sucks the sap, it enters its digestive system, killing the insect pests, Such insecticides are required in less amounts for sprayll1g, Pathogens are always present in the environment and when they get favourable conditions for their growth, they infect the plants, These pathogens are transmitted through the soil and seed, water and air. Soil, water and seed borne diseases mostly infect roots and stems, whereas air borne diseases attack the aerial parts of plants, Soil and seed borne diseases can be controlled by treating soil and seed, Air borne diseases are controlled by spraying fungicide solution on infested parts of plants. Precautions All pesticides should be used according to the recommended dose, At the time of use, instructions written on the packet should strictly be followed. It may cause harm to the human beings and livestock, Pesticides should be kept well packed and away from the reach of children, Person spraying pesticides on crops should keep his mouth and nose covered, Avoid direct contact with pesticides; it may be harmful to human beings.
I
2. Biological Methods of Pest Control
It includes deliberate introduction of living material (parasite, predator or pathogen or an animal pest) into the environment of the pest so that its population density may be reduced or damaged. The living material is a natural enemy of the pest. For example, ladybird beetles and praying mantis devour the scale insects and aphids, feeding on plant sap, Insect pests are also controlled by bacteria called Bacillus lhuringiensis, These bacteria enter the body of insect pest, multiply and kill them, Fig. 3.8 Rust disease of wheat
- --
~""./',,-
108
Improvement in food Resources
Table 3.9 Control Measures of Insect Pests of Major Crops S. No. I.
I
Name of insect pests
Name
of the crop
I
Common
name
Rice (Oryza I. 1. Gundhi sativa) bug
Scientific name
Leplocorisa vancorrus
Nature of damage
I
!
INymphs
Control measures
and adults suck II. the sap of tender grains. Affected earheads stand erect like normal ones, 2. but without any grain formation. Attack is during post-flowering time.
Plough the land immediately after hanest and destroy stubble. Spray with Manacrataphas at the rate of 0.5 kg/hectare or 0.04% Diazinon or Phosphamidon or Fcnitrothion.
2.
2. Leaf hopper
TeUigella spectra
Both nymphs and adults Spray ~10nocrotophosat the rate suck sap from young leaves. of 0.5 kg/hectare or Spray 0.4% Infested leaves turn yellow. Phosphamidon or Diazinon.
I. Gujhia weevil
Tanynecus
indicus
Grubs feed on roots and adults cut the growing points.
Mix 5%, Aldrin dust in the soil before sowing at the rate of 20 kg/ hectare. For adults, dust 5% BHC.
Maggots attack seedlings and kill the central shoots, causing dead hearts.
Application of 10% Phoratc or Disulfoton (5%) to the soil at the
TfJporhyza nivella
Larvae bore into the midrib of leaves, make tunnels enter into the growing point and damage it.
Apply I kg of Phorate granules at the rate of 20 kg/ hectare at the base of shoot in June. Also spray 0.05% \lonocrotophos.
Chilo infuscatellus
Larvae bore into the central Apply Lindane 51 kg/hectare in shoot and make tunnel 800-1000 litre water in furrows downward. Larvae feed before planting. inside on the soft tissues.
3. Leaf hoppers (pyrilla)
Pyrilla perpusilla
Both nymphs and adults suck sap from underside of leaf.
Spray Endosulphan 35G at the rate of 1.251 kg/hectare. Dust 5% BHC or spray 0.03% \lonocrotophos.
Pod borer
Heliothis Sps.
Larvae first feed on tender leaves. Later on, they make holes in pods and feed the developing grain.
Spray Carbanl at the rate of 1.5 kg/hectare.
Groundnut White grub
Laclmosterna
consangumea
Grubs feed on roots and kill plants.
Apply 10% Ph orate granules.
(Amchis hypogaea)
Adult beetles feed on leaves.
Application of Thimet 10 G granules at the rate of 20 kg per hectare before sowing.
Nymphs and adults suck sap from the leaves and other tender parts of plants.
Spray 0.5% Lindane, or 0.02% Phosphamidon or Spray metas\Stox 25 EC at the rate of 11 kglhectare in 1000 litre water.
Affected leaves get curled and plants wither and die.
Dusting with 5% Malathion at the rate of 20 kg! hectare, or Dust 5-10% BHC or 4% Carbaryl.
Wheat
(Triticum aesitivu:m) I
2. Shoot fly
I
3.
Sugarcane
(Saccharum officinarum)
I. Top
borer
2. Shoot borer
4.
5.
Chickpea (gram)
Atherigona naqvn
I
6.
,
~1ustard
(Brassica campestris)
\1ustard aphid
Painted bug i I
.' _'ovement in Food Resources
Lipaphis e'JSl11u
Bagmda cnlciferarum
time of sowing.
Both nymphs and adults suck the sap of leaves at the seedling stage and devitalize plants.
109
~
/ .•
Crop Diseases Diseases produce disorders in the body due to harmful physiological changes. The causative agents like bacteria, virus and fungus change the normal physiological process. Thus, certain distinct symptoms appear. Diseases cause the loss of amount of plant products in the field and also in store. Plant diseases have been classified into the following three categories: (1) Soil borne diseases: Their pathogens are found in the soil and under favourable conditions the pathogens infect the roots either at a seedling or an adult stage of the plant. Examples are smut of bajra, tikka of groundnut. (Fig. 3.9). (2) Air-borne diseases: Their pathogens (fungi) are found in the air. They infect the aerial parts ofthe plants, e.g., shooLS, leaf, flower and fruits. Examples are rust of wheat, rust of gram, blast of rice, mildews, etc. (3) Seed-borne diseases: Some pathogens (fungi) live dormant in the seeds and other propagative organs of the host plants. These dormant pathogens become active when infected seeds germinate and cause infection, e.g., ergot of bajra (pearl millet), leaf spot of rice, loose smut of wheal, covered smut of barley. (4) Water-borne diseases are transmitted through water, e.g., blight of rice (bacterial).
Fog 3.9 Tikka disease of groundnut
I
Control of Plant Diseases
Control of plant diseases is necessary to prevent the quality and quantity of yield. Import only disease free seeds and propagative parts. Many pathogenic fungi complete their life cycles in two hosts. Alternate host provides shelter to the pathogen under unfavourable conditions, destroy this alternate host so that the pathogen's life cycle does not complete. By crop rotation pathogens can also be minimised or destroyed because then they will not get an alternate host for completing their life cycle. Compounds of sulphur, mercury, arsenic, zinc and copper are also used to control plant diseases. Table 3.10 Important Diseases of Major Crops and their Control Measures Name of the crop Rice (Oryw sativa)
Diseases Common name
Blast
j
Symptoms
Causative organism
Piricu/o,ri orywe
Control measures
Brown boat-shaped lesions on Treat seed with thiram solution in water (2.5 g/kg seed ). Spray Bavistin (l gil water) at 10 days
leaves, stem and grains.
interval. Treat seeds with Agrosan
G'\ (2.5 g/kg) before sowing. Bacterial
Xanthomonas
blast
orywe
Watery yellow lesions with brown margins on leaves.
Later the whole plant may appear blighted. Wheat
Rust
Puccinia
grmmmntS
(Triticum aestivum)
Brown rust-colour elongated SpOLS on leaves and stem. Grains develop black powdery
Grow tolerant varieties of rice
like IR-20 and Pusa 2-21. Treat seed with mixed solution of Streplocycline (0.015%) and wettable ceresan (0.05 %). Spray Dithane M45 at 2g/1 water at 10 days intervals.
smut in them.
Sugarcane
Red rot
(Saccharum officinarum)
./.~--
Colletotrichwn falcatU1n
Small red spots on leaf mid Grow resistant varieties. Treat rib appear. Leaves wither. Pith seeds with Areton or Agallo (0.25%) for 5 min before sowing. of sugarcane turns reddish. Improvement in Food Resources
110
"
L"--
_
Gra"y shoot
I Chickpea (gram)
Wilt
Pigeon pea
Stem rot
Mycoplasma
1'roduction of many thin tillers from the base. Sprouting of lateral buds.
Treat seeds with hot air at 54'C for S hours. Use healthy seeds.
Fusarium
Leaves become yellow and dry up. Roots turn black and decompose.
Deep sowing at 8-10 em depth in the light soil.
Development of dark brown
Mixed cropping of sorghum and chickpea. Avoid water logging.
oxysponL1n Diplodia cajani
lesions on stem near the soil
surface. Girdling of stem leading to death of the plant. Groundnut
, (Arachis hypogaea) ~ustard
Tikka or leaf spot
Mycosphae,~lla
berkeleyii and Mycosphae-rella arachidicola
'Vhite rust
Albugo candida
Downy mildew
Peronospom brassicae.
(Brassica campestris)
Light brown oval-shaped lesions on leaflets, petiole and
Spray Bavistin (0.05 %) at 15 days intervals. Grow resistant varieties.
stem.
Cream yellow or white pustule Spray Dithane Z-7S or Dithane on the lower surface ofleaves. M45 at 2g/1 in water. Remove and burn affected plant debris. Yellow irregular spots on Remove and burn affected plant debris. Spray the crop with 0.2% leaves. Inflorescense is malformed, twisted and bent Ziram or l\laneb. with 'white powder in severe infections.
Weed Control in the Fields Along with the crop plants, certain unwanted plants also grow in the fields. These unwanted plants are called weeds. These weeds adversely affect the growth of the crop plants, since they also absorb soil nutrients, water, fertiliser and manure, and take sunlight for photosynthesis. This causes decrease in growth of crop plants and their yield. Hence, their removal is essential. Weeds may act as an alternate host for certain microorganisms and insects and pests, which develop on them. These later attack on crop plants affecting their growth and yield. Some weeds produce ubstances which may be toxic to crop plants, inhibiting their growth. Seeds of weeds may also be harmful to human beings when mixed with seeds of crop plants. Say, for example khesari dal produced along with arhaT dal in Madhya Pradesh is poisonous or human beings.
1. Common Weeds Weeds share the same habitat. In some cases weeds may be a crop plant another crop, such as mustard plants in wheat crop. But they are sown along ,;th wheat in a separate line on an elevation. Wheat plants of C-306 (tall variety) e weeds in the field of wheat HD-2687 of dwarf variety. Growth of weeds is more kharif crop in comparison to rabi crops. Bathua (Chenopodium) which we eat in -inters grows abundantly in wheat fields as a weed. Weeds in different seasons and different crops vary. Amaranlhus (chaulai) is a common weed that grows with all ops. Arge11lone with yellow flowers is also a weed.
~owing with
Weeds are of two types: (i) Broad leaved weeds, like chaulai, (Amaranthus), bathua (Chenopodium). These are dicotyledonous. They grow in a monocotyledonous crop such as cereals. Ivernen! in Food Resources
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VK Biology IX 1----,
(ii) Karrow leafed weeds. such as wild oat, grass, etc., are monocotyledonous.
Chenopodium
Amaranthus
Convolvulus
Wild Oat
Grass
Fg.3.10 Certain common weeds
Table 3.11 Weeds of Different Crops Crops
Broad-leafed weeds
Narrow-leaved weeds
Kharif (maize, Jowar, Amaranlhus viridis (Chaulai) Cyperus mtundus (nut grass, motha), bajra, pulses, rice) TTiamhema (saathi) wild sorghum Gangli jowar) Rabi (wheat, barley, Chenopodium album (bathua) PhalQ17s (mandoosi), wild oat Gangli pea, gram, etc.) Convolvulus (hirankhuri) jari)
I
2. Weed Control Methods
Removal of weed plants from a crop field is called weeding. Weeds can be controlled mechanically, chemicaJly and biologically. (i) Mechanical methods: Weeds are removed by picking them manually or by
harrow, ploughing, and tilling, mowing or cutting with machines. (ii) Chemical methods: Weeds are also destroyed with the help of weedicides or herbicides. Herbicides are applied to the foliage of weed or to the soil three times: pre-planting of crop; after planting, but before emergence; after emergence. They may damage the weed either by contact with the roots or with foliage or after translocation through the roots or through the foliage. Herbicides (inorganic) are sulphuric acid, obtained as Bov-brown oil of vitriol, sodium chlorate, borax, and crude sodium borate. Organic herbicides are auxin-type growth regulator. MCPA, 2 methyl-4-chlorophenoxyacetic acid and 2, 4-dichloro-phenoxyacetic acid kill many annual and perennial weeds in cereals without damaging the crop. (iii) Biological methods: Control of weeds is done by using insects which feed selectively on a particular weed. Certain microorganisms are also used to kill the weeds by producing disease. Cochineal insect control the growth of prickly pear weed (Opuntia). Control of aquatic weeds is done by growing fish, like grass carp. Millet, barley, soyabean, etc., crop plants do not allow the growth of weeds. These crops are called smoother crops. (iI') Cultural methods: Prepare proper seed bed, crops should be sown at proper time, crop rotation and intercropping are beneficial to control weeds.
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VK Biology IX
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Improvement in Food Resources
Scientific Storage of Food Grains It is very important to preserve the stored food grains from losses due to insect pests, other pests, fungi, etc. Food grains are stored either for future human consumption or for seed purposes. Improper storage conditions cause insect infestation. Deterioration in quality and quantity of food grains also occur due to improper storage of food grains. About 100 crores loss occurs annually in stored agricultural produce, i.e., about 9.3% annual loss. Beetles and moths are important pests of stored grains. In case of beetles, grubs and adults, both attack the stored grains, while in case of moths, only caterpillars damage the food grains.
Pulse beetle
Khapra beetle
Rice weevil
\.
Rice moth
Lesser grain borer
Grain and flour moth S O'M
Rust red flour beetle
gra nt
Food grains are stored in silos (FCI, Food Corporation of India) and also in gunny bags in large store houses by FCI and also by traders. Farmers also store wheat in gunny bags in large rooms along with wheat plants husk (bhoosa). During the storage of food grains damage occurs mainly by two factors:
I
(1) Biotic Factors
These include insects, rodents (e.g., house rat and mouse, and squirrel, etc.), birds, mites, bacteria and fungi. Birds like parrot, parakeet, pigeon, bulbul, etc. damage the standing mature crop. A few insect pests of stored grains are: (i) Grubs of Pulse beetle or gram dhora (Callosobruchus maculatus) damage stored
grams. (ii) Grubs and adult beetle of rice weevil (Sitophilus oryza) damage rice. Larvae of
(iii) (iv) (v) (vi)
rice moth (Corcyra cephalonica) damage rice and maize. Wheat weevil or Khapra (7i·ogodenlla granariwm) damage wheat grains. Caterpillars of grain and flour moth (Sitotmga ccrealela) bore into grains of wheat, rice, barley, maize and jowar. Adult and larvae of rust red flour beetle (7iibolium castanewn) damage wheat flour. Grub and adult beetle of lesser grain borer (Rhiwpcrtlza dominica) damage grains, feeding on inner material.
(2) Abiotic factors Moisture or humidity and temperature are the abiotic factors. provement in Food Resources
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VK Biology IX
Temperature Maximum growth ofinsects occur at 30°C to 32°C temperature. Microorganisms become active at 30°C to 40°C. The food grains, thus, should be stored below 30°C, at which microorganisms and insects remain less active, causing less damage. Vegetables and fruits require 1°C to 7°C for preservation. Meat and fish are stored at 3°C to 8°C and 7°C to 10°C respectively. Moisture Food grains should be dried before storage. Moisture content of grains should not be above 14 per cent by weight. Moisture above this level causes decay to grains by helping in the growth of microorganisms and insects. Microorganisms and insects release heat during respiration, which cause a rise in temperature ofthe space. This heat is called dry heat. Humidity Humidity in air promotes growth of moulds like MUCOT or Penicillium over the grains. These cause decay of grains. Therefore the storage houses should also be dried before storage. Humidity more than 14 per cent also cause germination of grains leading to rise of temperature. This rise of temperature of food grains due to growth of fungus and germination of seeds due to more humidity is called wet heating or damp-grain heating. Both dry heating and wet heating reduce the quality of stored grains. They also affect the germination of seeds. Thus, biotic and abiotic factors cause infestation of insects, degradation of grains in quality, weight and germination, etc. Such crop produce fetch low market price causing economic loss.
I
Preventive Measures before Food Grain Storage
The following preventive measures should be taken before storage of food grains in storage houses:
Fig, 3.12 Penicillium
Fig. 313 Yeast
:.-----
.
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VK Biology IX
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(I) Drying: The moisture content of crops at the harvest time ranges from 15 to 35 per cent. Grains also absorb moisture from the atmosphere, if humid conditions of the environment prevails. The moisture content in grains should be below 9 per cent. If it is above this prescribed limit, it will cause decay of food grains by microorganisms (e.g., bacteria, fungi) and insects. Therefore, the food grain crop should be dried first in the sun and then in shade. For drying, it should be spread thinly on the cement floor. Mechanical driers are also used for drying on a commercial scale. They blow hot air. Removal of foreign particles from food grains, such as weed seeds, earth particles, stone pieces, straw, etc., is also essential before storage. Thus, crop of food grains should be well sieved. (2) Maintenance of hygiene of store houses: Storage places like warehouses, bins and godowns should be clean. They should be devoid of dust, dirt, rubbish, webbing or refuse of previous grains. The cracks and holes in the walls, floor and ceiling should be sealed by cement. Gunny bags used for storage of food grains should be new. If old gunny bags are to be used, they should be turned inside out and then dried in the sun and fumigated or sprayed by insecticides and fungicides. If any moisture persists in the bags or any' fungal infection is present, it will damage the grains. Earthen pots (matka, etc.) used in villages should also be dried and cleaned. Food grains should also be dry, cool and clean. Mouths of gunny bags after filling the grains should be stitched properly. The grainfilled gunny bags should be stored in store houses in tiers, one above the other and there should be space in between tiers for inspection and Improvement in Food Resources
fumigation if needed. Gunny bags should not touch the side walls, otherwise they may get moisture. Storage places should also be dried before storage. (3) Prophylactic treatment: Storage places should be sprayed with insecticides, fungicides, etc. or fumigated for making them free from microorganisms and pests. If the grains are used for sowing, they should be mixed with proper insecticides and fungicides. Gunny bags, especially the old ones, may also be fumigated or treated with pesticides before fIlling grains. (4) Improved structures for storage: For safe storage of grains improved storage structures should be used, such as pusa bin, pusa cubicle, pusa kothar and pant kuthala. These structures are air tight, moisture proof, thermally insulated and rodent proof. • (5) Silos: These are used for large scale storage of grains. These are large and tall cylindrical steel structures, having outlets (chutes) at different levels to withdraw the stock of grains when required. They are built-in arrangements for temperature control, aeration and fumigation, etc. They are all proof, i.e., insects, birds and mammals cannot damage the grains. In silos large quantity of grains can be stored. Gunny bags are not required in silos. Silos are located in Hapm (Uttar Pradesh).
Control Measures against Pests
,
Fig 314 Agrain·silo
Grains stored for human or animal consumption should not be mixed with any type of pesticides, but they may be fumigated. Seeds for sowing purpose can be mixed with pesticides for keeping them free from every type of infestation. Pest infestation of stored grains can be avoided by the following techniques: (I) Chemical control by insecticides: Insecticides are sprayed or dusted on stored grams. Spraying of insecticide solution is done by manual sprayer or mechanical sprayer. In this method, only surface layer ofgrains get sprayed. Gammaxene or benzene hexachloride wettable powder (BHC WP), pyrethrum and malathion are used for spraying the storage places at 3 weeks' intervals. Preparation of spray solutions are as follows: BHC WP (50 per cent):
31 10 0 m 2 area in 1 : 25 dilution.
Pyrethrum (2.5 EC):
31 2 10 0 m area in I : 300 dilution.
Malathion (50 EC):
31 2 10 0 m area in I : 300 dilution.
(2) Fumigation: In fumigation, the solution of pesticides is converted into fumes (vapours). Fumigants should be toKic to insects and mites. It should penetrate the material to be protected easily and it should not damage the material or leave harmful residues. It should not be phytotoxic. Fumigants enter the pests' body through spiracle. Fumigants are most-effective in closed spaces. They are widely used for the control of stored-product pests. provement in Food Resources
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VK Biology IX
The following are the chieffumigants: (i) Carbon disulphide used on grains. (ii) Ethylene oxide used on grains, cereals and some plant products. It is also (iii)
(iv) (v)
(vi)
toxic to some bacteria, viruses and fungi. Aluminium phosphide (AlP) tablets (black poison), each is of 3 grams. These are used at the rate of 2 tablets per tonne grain or 160 tablets per cubic metre volume of grain. 3 : I mixture of Ethylene dichloride plus carbon tetrachloride (EDCT) in liquid form is used at the rate of 30 mU I 00 kg grain. Ethyle dibromide (EDB) in liquid form is used at the rate of 3 mL for one quintal (100 kg) wheat. It is available in glass ampoules ofdifferent capacities. These are found wrapped in clothes. It is inserted deep in the storage grains and is broken. It is gradually converted into fumes into the grains. Storage place should be sealed for good results. Methyl bromide at 16 g per cubic metre is also used.
(3) Plant products: Grains of legumes are protected from insects by smearing the grains with a small quantity of vegetable oil or mineral oil. This practice is very old and used in villages. Cowdung burnt hot ash is also mixed with grains of legumes to protect them from pest attacks. Such treatment prevents egg laying, reduction in egg hatching, interferes in larval development, i.e., very few hatch as adults. Control of insects is also done by mixing of neem kernel powder and crushed dried fruit of black pepper.
I
Precautions for Handling Pesticides
Pesticides are poisonous to some extent to human beings, domestic animals like dogs, cats, cows, etc. Therefore, they should be stored carefully beyond the reach of children. Their application also need precaution-nose and mouth should be covered with a cloth, gloves should be used, etc. Also dispose off the leftovers carefully.
FOOD RESOURCES: ANIMALS
-
,.,t'·....·~--- VK Biology
Since ancient days, man has been dependent on animals for food and clothing. The primitive men obtained animal food mainly by hunting them. Later he domesticated animals for milk, meat, eggs and fur. These animals were cow, buffalo, sheep, goat, pig, horse, donkey, camel, mule and hen, etc. These animals were called domestic animals and when he started doing agriculture, he took the help of bullocks for ploughing the fields, pulling carts and carrying loads. Cows provided milk. Cows were worshipped since time immemorial only because both their progenies-males and females were of immense use to man. Nowadays in machine age, bullocks are replaced by tractors. ow male and female buffaloes are in use, females for milk and males for carrying loads and pulling carts.
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Improvement in Food Resources
Now a special branch of agriculture has been developed for feeding, rearing, improving animal breeds. This is called Animal Husbandr~. The term livestock is used for cow, buffalo, sheep, goat and pig, etc., which are raised on a farm. Animal food is rich in proteins. Y1i1k is a nutritious food rich in proteins, carbohydrates (lactose sugar), fats, vitamin A and 0, minerals (phosphorus, calcium) and water (90%). Fish meat is also rich in protein, fat, vitamin A and D. Animals, insects providing food can be divided into following categories:
• Animal husbandry includes rearing, feeding and improving their bluds.
(l) Milk-yielding animals like cow, buffalo, sheep and goat. These animals are
called milch animals. (2) Meat and egg-yielding animals, like hen (poultry), duck, goat and fish provide eggs and meat. (3) Honey yielding insects like bees (apiculture), for providing honey, wax, etc. Table 3.12 l\;utritional alue of Various Animal Products (Amount of . 'utrients in Percentage) T
IS. No.
I
I.
Animal products 'Cow milk
I
Fat
Protein
Carbohydrate (Sugar)
Minerals
Water
3.60
4.00
4.5
0.70
87.20
2.
~1eat
3.60
21.10
' Little amount
1.10
74.20
3.
Fish meat
2.50
19.0
Little amount
1.30
77.20
4.
Egg
12.0
13.0
Little amount
1.00
74.00
Department of animal husbandry is doing an immense work in improving the breeds of cattles (cow, sheep, goat and buffalo), pigs and poultry. It resulted in a remarkable increase of milk yield from improved breeds of cows and buffaloes, and poultry products from poultry. Table 3.13 Comparison in the Production of Animal Food since 1970. Year
Egg (crore tonnes)
Fish (in lakh tonnes)
,
Milk (Iakh tonnes)
1970
60
17.56
170
1980
1300
24.42
302
[990
1960
32.00
5[5
2000
3355
5656
780
The increase of egg production brought about a silver revolution in the field of animal husbandry. It is especially done in the states of Punjab, Haryana and Uttar Pradesh. Egg consumption especially in winters has also been increased in northern states of India. Similarly, production of milk has also increased remarkably because of Operation Flood Programme. All this has happened due to the development of high milk yielding cattles (cows and buffaloes) by the efforts of government and private organisations. In Maharashtra, milk yield has increased many times. Mother Dairy is largely purchasing the milk from the dairy cooperative societies, which directly purchase from the individual farmers. Dr. V. Kurien, born on 26th Nov. 1921, is the founder chairman of National Dairy, Development Board C\fDDB). He designed and implemented the 'Operation Flood', World's largest dairy development programme. Dr. Kurien is the architect of modern dairy industry and father of white revolution.
Improvement in Food Resources
Dr. V. Kunen
117
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Milk Producing (Milch) Animals Milk-producing animals are cows, buffaloes, sheep and goats, but mainly cows and buffaloes provide almost the entire milk to the dairy industry. Artificial feeds and nutrient food are manufactured to improve the milk yield of cows. The male animals (ox) are used in agriculture for labour (carrying loads) and are also for providing meat and hide. Buffalo meat is exported to Gulf countries (Saudi Arabia, etc.) in sealed tin packs. The products produced from the milk are ghee, butter and cheese, etc. Their excreta (dung) is used as manure and also in producing gas (gobar gas) for cooking and lighting purposes.
Fig. 3.16 Ayshire
Dairying is the production and marketing of milk, usually of cow and buffalo and its products (butter, paneer and ghee). Dairying includes care of cows, their breeding, feeding, management and milking. Breeding techniques and application of genetics in stock improvement programmes of cattle (cows and buffaloes) has increased the production of new breeds with high milking capacities.
I Important Breeds of Cows and Buffaloes
Fig 317 Murrah buffalo
There are many breeds of cows and buffaloes ll1 our country. Buffaloes are mainly restricted in northern states of India. Various breeds of cows are classified into three categories: draught, dairy and dual-purpose breeds.
I. Draught breeds: These are strong and sturdy animals used mainly as beasts
of burden. These are used for drawing bullock carts, ploughing land and transportation. Cows ofthese breeds give less milk. 2. Dairy breeds: These cows are high milk yielders but bullocks are poor for draught purposes. 3. Dual purpose breeds: These animals serve two purposes well. The cows are good milk yielders and bullocks are good for draught purposes. In India (rural), cows are of various breeds-indigenous (Indian), exotic (foreign) and cross breeds for dairying. Cross breeds are developed by mating bulls of exotic breeds and cows of Indian breeds.
I
Indigenous Dairy Breeds of Cows
These are Deoni (found in Andhra Pradesh), Gir (Native of Gujarat, medium in size and good milk yielders), are found in Rajasthan, Maharashtra and Baroda. Red Sindhi (medium sized and red in colour with dark and light red shades) found in Punjab, Haryana, Odisha, Karnataka, etc., Sahiwal (large and of heavy build and are superior to other breeds) found in Punjab, Tharparkar (grey Sind hi) found in Rajasthan, Maharashtra and Haryana. Deoni, Tharparkar and Haryana are dual purpose cows and are fairly good milk yielders. Buffaloes Indigenous breeds of buffaloes are Nagpuri, Jaffrabadi, Mili-ravi, Mahsana, Surti and Murrah. ~lurrah is the breed of Punjab and Haryana. Its average yield of milk is 1800 to 2500 litres with fat contents about 7 per cent. Mahsana is the breed of Gujarat (Vadodara and Mahsana districts). Their milk yield is about 1200 to 2500 litres. They start giving milk at a comparatively early age. 118
,
~~''';
Improvement in Food Resources
Surti is also the breed from Gujarat (Districts of Vadodara and Kaira). Their average milk yield is 1600 to 1800 litres with a fat content of about 8 to 12 per cent. Exotic Breeds of Cows Exotic breeds are those which are imported and reared in India. Exotic breeds are crossed with indigenous breeds to obtain cross-breeds. These have good, desirable characteristics than pure indigenous forms. Imported breeds of cows are Holstein-Friesian of U.SA, jersey (U.SA), and dual purpose cow Swiss (European Brown) and Gurnsey (English). Improved Breeds of Cows Indigenous breeds of cows have been crossed with the exotic breeds of bulls to produce high milk yielding cows. Exotic breeds like jersey, Brown swiss have long lactation periods, while local breeds like Red Sind hi and Sahiwal show excellent resistance to diseases. The tlVO are crossed to obtain offsprings with both the desired qualities. The improved high-yielding breeds of cows produced in India are Frieswal (crossbreed of Sahiwal and Holstein_riesian), Karan swiss (crossbreed of swiss and ahiwal), Karan-Frieswal (crossbreed ofTharparkar nd Holstein-Friesian), jersey, Holstein-Friesian and Murrah. Lactation (milk production) period is the period between the birth of a young one and the Fig,3.18 next pregnancy. It usually lasts for about 300 days. Lactation period of various breeds and milk yield is given below:
Improved high milk-yielding cow (Holsteln-Frieslon)
Ftg. 3.19 Improved htgh m ,-y:eld ng cows
Table 3.14 Improved Indian Breeds and their Milk Yield Name of Breed
' Milk Yield in litres in one
Lactation Period
Lactation Period
Gir Red Sind hi Sahiwal
1200-2200
320 days
700-2200
298 days
1100-3100
310 days
Holstein
3200
365 days
Kanarei
1400 700-2200
-
3500
-
2000
-
Tharparkar Karan-Frieswal ~
urrah (buffalo)
ovement in Food Resources
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119
Breeds of Sheep and Goat Sheep is largely reared by poor people. It provides milk, meat and hide. Their excreta is used as manure. Likewise goats are reared for milk, meat, wool and hide. These are also reared by poor people. They both need less space as shelter. Goat wool is used in making rough blankets and pullovers in rural India and in hills. Important breeds of sheeps are Gurej, Lohi, Bikaneri, Gaddi, Rampuri, Mandya, Bhakrawali, Nellore, Marwari and Deccani. Important breeds of goats are Jamunapari, Barbari, Bengal, Kashmiri, Marwari, Gaddi, Pashmina, Surti and Malabar.
Breeds of Poultry Birds Poultry includes fowls, ducks, geese, turkeys and guinea fowls. Poultry mainly deals with fowls (hens). Poultry breeds are reared for eggs and meat. Poultry forms a substantial source of food protein for human beings. Poultry farming is easy to start and maintain in a small space and with a little finance. It gives quick return.
Green Jungle Fowl
Grey Jungle Fowl
~"
Red Jungle Fowl
White Leghorn
Barred Plymouth F~.
3.20 Poultry breeds
I
Indian poultry breeds provide good quality meat but they lay less number and small sized eggs. A desi hen lays about 60 eggs per year, whereas exotic breeds lay larger and more number of eggs per year. Desi hens are comparatively strong and immune against diseases in com parison to exotic hens which require more protection and immunization against diseases. The breeds are crossed to obtain offsprings with both the desired qualities. With the introduction of exotic breeds of fowls, poultry farming has gained considerable importance in India. It has now become popular and thousands of farms have developed in India, where a large number of fowls are bred and reared for egg and meat production.
Poultry breeds 1. Indigenous (desi) breeds of poultry birds: These are Aseel or Indian game (high yield of meat but not good egg layer), Basara, Chittagong, Ghagus, Brahma and Kochi. Peela (golden red), yakub (black and red), nurie (white) and kajal (black) are other Indian breeds. 2. Exotic breeds of poultry birds (hen): These are white leghorn (small body size, egg long and white, needs less food for maintenance), Rhode Island Red (yields good meat and fairly good egg layer), Black Minorcha, Plymouth and Light Sussex. These birds are bred and acclimatised to the local conditions. These birds were brought here by European residents. These birds lay more eggs than the indigenous birds but give less meat. 3. Improved breeds of poultry birds: These are White leghorn, Minorcha and Rhode Island Red. Other improved breeds are B-n, H 260 and IBL-80. These take less food but lay more eggs, i.e., about 200 to 300 in a year, and provide more meat. Indigenous (desi) breeds of hens resemble the leghorn breeds in size and shape. Desi breeds are not good egg layers. The desi hen is the best mother and an ideal sitter. The desi breeds are Aseel, Chittagong, Brahma and Ghagus, etc.
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VK BIOlogy IX
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Improvement in Food Resources
Aseel birds are good for meat, which is plentiful, delicious and have a pleasant flavour. They are not good egg layers. Chittagong are comparatively good egg layers. Their meat is delicious. Ghagus are fairly good egg layers and good sitters. Its meat is delicious and used for table purposes. The most popular exotic breeds in India are White leghorn and Rhode Island Red. White leghorns are not good for meat purposes but are good in egg production. Rhode Island Red is good for meat and eggs. This is kept in Government poultry farms. Its chicks grow quickly and so are reared easily. The present day fowls reared for eggs or meat are cross breeds of Leghorns and Rhode Islands with indigenous breeds.
I
Poultry feed
Feeding of poultry birds is important for rearing. The quality of food is responsible for the growth of birds, egg-laying efficiency and quality of eggs produced. Their diet includes adequate amount of water, carbohydrates, proteins, fats, vitamins, minerals etc. Maize, sorghum and wheat are a good source of carbohydrate. Groundnut cake is widely used as a protein food. Tissues of animals like fishes, slaughter wastes and blood from slaughter houses, etc., are an ideal protein source.
I
Poultry care
They should be provided good food and clean hygienic shelter. Poultry farming needs care for food, shelter and disease contro!' First phase oflife of poultry is the growing period upto sexual maturity. In this period chickens are called growers and they require enough space for proper growth. They need restricted and calculated feed for normal growth. Period from sexual maturity upto the end of egg laying is called laving period and chickens are called layers. They also require enough space and lighting. Light intensity and duration oflight effect the laying output of hen. Broilers (meat yielders) are used for getting meat. They require protein rich food with adequate fat. Poultry feeds are rich in vitamin A and K. These birds should get good housing and environmental conditions for their fast growth and low death rate.
I
Poultry disease
Poultry birds also suffer from diseases, which may be caused by bacteria, viruses, fungi and other parasites. Over-feeding also causes sickness like crop bound, diarrhoea, dysentery, etc. Ticks also cause tick fever, feed on blood oHow!. To protect them from diseases, it is necessary to provide good food, and shelter should be disinfected from time to time. Vaccination is also a control measure for certain diseases.
Fish Fish is a rich protein diet for human. Fish industry in India is about 1,500 years old. Fishes provide valuable source of food supply to the inhabitants of the countries located in tropical regions. Fish meat contains 60 to 80 per cent watel~ 13 to 20 per cent protein and fat. It also contains vitamins and phosphorus. Fishes are of two types: Marine and freshwater. Both are used as food, but not all marine fishes Improvement in Food Resources
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VK Biology IX
---.:::,
are used as food. For fishing, our inland water area is about 1.6 million hectares and coastal line is about 6,500 kilometres. Thus, our country has a great potential for fishing industry. Besides food, fish also provides a number of other products: 1. Fish oil: Fish liver oil is extracted from liver which is of great medicinal value. It contains vitamin A. In some fish, liver oil contains vitamin C, D and E also.
Fish liver oil is extracted from cod fish, tuna, sharks, etc. 2. Industrial use: Fish protein is extracted from fish wastes by removing fats. It is dried and obtained as white powder. It contains 80 to 90% soluble protein. It is used in the preparation of ice cream, paints, varnishes, cosmetics, etc. Fish flour is used in biscuits, bread, cakes and soups, etc. It is easily digestible. 3. Agriculture use: Fish wastes are used as manure for coffee, tea and tobacco crops. Fish manure (dry powder form) contains nitrogen, phosphorus and calcium. Dried fish are provided to farm animals, which are good protein sources. 4. Adhesive: Fish glue is obtained from skin and bones of cod, haddock, pollak and hake. The residue obtained after extraction of glue is used as a poultry feed and fertiliser after drying.
I Common Edible Fish of India Fish on the basis of habitat are of three types: Marine or sea fish, brackish water fish and freshwater fish. 1. Marine fish: These are mackerel, sardines, salmon, bombay duck, etc.
2. Brackish water fish: These are mullet, pearl spot, etc. 3. Fresh water fish: These are catla, labeo (rohu), mrigal and reba. Cat fish are Wallago, Mystus, singhi and magur. All are used as food. Catla is a fast growing fish. Fisheries
Calla (carp)
Labeo (rohu)
Rearing of fish on commercial scale is called fisheries. Fish are reared in ponds, lakes, rivers, etc. The culture of fish is termed as Pisciculture. Fish culture involves collection of eggs from natural water systems (rivers, lakes), hatching and nursing in nursery ponds and harvesting. Han'esting is done when the fish attains the marketable size. During nursing and rearing, fish are protected from water beetles, bugs and frogs (they can cause harm in fish nurseries), birds and snakes. Fish are also protected from Infectious Pancreatic Necrosis (lPN) and Viral Haemorrhagic Septicemia (VHS). River and pond water pollution from industrial and urban wastes (sewage) is harmful to fish. The Central Institute of Freshwater Aquaculture (CIFA), Bhubaneswar, has been doing enough work on breeding and rearing the catfish (magur). It is an air-breathing fish. Central Inland Fisheries Research Institute, Kolkata is also doing work on fisheries.
Channel (catfish)
Fig. 3.21 Various Indian freshwater fish
-----II'fiWilliIDli'l' I ."..-J:
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Improvement in Food Resources
I -_
•RMATlVE ASSESSMENT
FA 3. :
1. Growing of wheat and gram on the same field is called
_
2. Planting of finger millet (bajra) + cowpea (labia) in alternate rows in the same field is called _ 3. Growing different crops on a piece ofJand in pre-planned succession is known as _ 4. The unwanted plant that grows along with the desired plant is called 5. Diseases in plants are caused by VIruses.
such as bacteria, fungi and
6. Fresh initiatives for mcreaSll1g the water available for agriculture include ______ and _
FA 3.8: Mapping.tvpe Worksheet (i) They cuts the root, stem and leaf. (ii) _ (iii)
_
Pests attack the plants in 3 ways
(c;~qo.
Pesticides include
~~r:.,(r:vcJ· ,~~=- L,...
r;
,u
-"~0~-,t"~
Plant diseases are caused by pathogens like
Excessive use of chemicals cause
Improvement in Food Resources
Commonly known weeds are
123
FA 3.9: Match the Following Match the terms in column I to their meanings in column II. Column I Column II (a) River Lift Systems (i) Wheat + gram or wheat + mustard or groundnut + sunflower (b) Weeds
(ii) Water is directly drawn from the rivers for supplementing irrigation in areas close to rIvers
(c) Inter-cropping
(d) Mixed cropping
(iii) Xanthium, Parthenium and Cyperinus rotundus (iv) Soyabean + maize or finger millet + cowpea
FA 3.10: Group Discussion Divide the class into small groups. Discuss cropping patterns, irrigation and crop protection management and discuss the following questions in your group. I. What is inter-cropping? Give examples. 2. Why should crop rotation be adopted? 3. What is mixed cropping? Give the advantages of mixed cropping system. 4. If there is low rainfall in a village throughout the year, what measures will you suggest to the farmers for better cropping?
FA 3.11: Model Making Worksheet Discuss with your parents or grandparents about various common agricultural crops that used to grow in their nearby farm lands years ago. Carefully note down all the factors that have changed in terms of • inigation • availability of nutrients-manure and fertilisers Collect all the information and try to present your information in the form of a model.
Animal Husbandry The breeding and rearing of live stock is called animal husbandry. Animal husbandry is a department under Agriculture which deals with the improvement of breeds of canles.
I
Breeding of Animals
Animal husbandry department is busy in developing good quality breeds of cow, buffalo, sheep, goat and fowl, etc., so that farmers get high milk yielding cows, buffaloes, sheep and goats. It improves the economic conditions of farmers. Breeding is done to produce breeds of cattle with desirable characters. Breeding for increased meat production and breeding for raising good milk yielding varieties or dairy breeds. In case of cows and buffaloes, increased milk and butter fat production has been the chief objective of breeding. Many breeds of cattle are available for cattle stock improvements. Pure form of a specific breed is cross-bred with local breeds to obtain cross-breeds to produce increased amount of milk like the pure breed.
VK Biology IX
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Improvement in Food Resources
Lactation (milk production) period is an important character among dairy breed cattles. Extended lactation with steady yield per day is a desirable trait. For a good breed, the daily yield will be about 20 to 40 kg of milk with 10 to 11 months of lactation. Dry days, period between lactation and calving during which cows do not milk, is short. Lactation capacity of a cow depends on the care and nursing during the conception period and the after delivery stage. Cross-breeding is defined as the crossing or mating of animals, belonging to two different breeds. The offspring thus produced will be of a better quality. The government has already established more than 150 government cattle breeding farms for dairy improvement. Artificial insemination is also a method to inseminate a cow during its heat period with stored semen. The semen of the desired bull (of exotic breed) is collected in a receptacle and then introduced into the female reproductive tract by man using instruments. The breeding of dairy cattle by this method has given the dairy industry the opportunity to make widespread use of superior breeds for improving the performance of dairy cattle. Artificial insemination was done for the first time on dogs by Italian Lazanno Spallarizani in 1780. In India, this was done in 1939 by Sampath Kumar in Mysore.
I
Advantages of Artificial Insemination 1. It makes selective breeding easier. Semen from any desired bull can be used
to inseminate any cow, selected for breeding. It gives the required type of offspring, with a better quality. 2. Attificial insemination is economical. The semen of a bull can fertilise a large number of cows. 3. Semen collected from a bull of desired trait can be stored (freezed) for a long time and can be transported to a long distance wherever needed. 4. Animal breeders can take semen from semen storage banks and thus, there is no need for them to keep a bull for this purpose. 5. Artificial insemination procedure is more reliable. Its success rate is higher than that of natural breeding. 6. Since semen is easily available whenever needed, a heated female can be impregnated easily. Milk is a very important supplementary diet of man. In India, milk is the only source of animal protein food for the vegetarians. In the infant stages of man, milk is the sale dietary food. Cows and buffaloes are the primary producers of milk, although goat and sheep also yield milk. Embryo transfer This technique is used for improving the animal breed. The developing embryo at a definite stage is taken out from the uterus of a superior breed and transferred into the uterus of a female of inferior breed. Here, it develops till birth. Thus, the quality and production in livestock can be improved.
Feeding and Shelter of Milk Animals For getting good, clean and proper yield of milk, the animals need daily regular brushing and bathing. Their shelters should be roofed to protect them from un's heat, rain and cold. The floor of the shed should be on a slope so that it is easily cleaned and it should also be dry. They should be spacious enough. A cow generally needs about six square metre space and a buffalo needs a little more space. The mprovement in Food Resources
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VK BIOlogy IX --'.' ,
cattle shelters should also be well ventilated. For their feeding there should be long feeding troughs and feeding passages.
I
Food The animal food includes roughage and concentrates. 1. Roughage largely contains fibres like green fodder. silage. hay of cereals and legumes such as barseem, lucerne, cowpea and agath. Green grasses are the most common nutritious food of cattles. These are Sudan grass. Rhodes grass, Napier grass. Guinea grass and Elephant grass, etc. Barseem, lucerne. cowpea and agathi are the leguminous fodder relished by cattles very much. Barseem and lucerne are available in winters as well as in summers. Jowar is also a green fodder of summers. Maize and bajra are used as dry fodder in summers. In winters, green upper part of sugarcane is also given to the cattles. which is also a nutritious food for animals. 2. Concentrates are low in fibres and contain relatively high proteins and other nutrients. Concentrates are rich in carbohydrates. fats, proteins, vitamins and minerals. Concentrate foods are cotton seeds, oil seeds. grains of maize, barley, oats.jowar. bajra. gram and their byproducts. e.g.• rice and wheat barns, gram husk. oil seed cakes. etc. Oil seed cakes (khal) in water is mixed with the hay of cereals to produce the nutritious nature of food. Cotton seeds are given to the cattles to increase fat content of the milk.
The daily (24 hours) balanced ration (feed) of a cow is as follows: I. Green fodder (roughage)
= 15 to 20 kg.
2. Concentrate (grain mixture) = 4 to 5 kg. 3. Water = 30 to 35 litres. Thus. milk-yielding cattles need a good nutritious feed daily for the production of fairly good milk. Additional vitamins, hormones and minerals may also be given to cattles for their good health, and good yield of milk. Antibiotics may also be given to them to protect them from diseases.
Diseases of Cattles Cattles (cows and buffaloes) suffer from various diseases. which cause reduction or stoppage of milk production. Certain diseases even cause death of the cattle. A healthy animal shows regular normal feeding. normal body posture. normal body temperature (38°C in cow) and pulse rate from 40 to 60 per minute. The normal respiratory rate is 15 to 30 per minute in cows. In buffalo, the body temperature is 37.2 to 38.2°C. pulse rate is 40 to 45 per minute. and respiration rate is 16 to 18 per minute. Diseases of cattles are of three types: (I) Parasitic (2) Infectious and (3) Non-infectious.
1. Parasitic diseases: Fleas. blood sucking lice. ticks and mites are external parasites. They live on the skin of cattles and cause skin diseases. Cattle leech (Hirudinaria granulosa) sucks blood of cattles (cows and buffaloes) and cause anaemia. Internal parasites of cattles are Ascaris sps. (worms) living in intestine, causing anaemia and intestinal disorders. and Fasciola sps. (flukes) damage the liver. 2. Infectious diseases: They are caused by bacteria and viruses. They are contagious and spread by contact from animal to animal. Bacterial diseases
iiidI
'---!
.:.~;
126
Improvement in Food Resources
are anthrax, black quarter, (from Clostridium chanroei) and haemorrhagic septicemia caused by Pasteurella multocida. Viral diseases are cow pox (Vaccinea), rinder pest and foot and mouth disease. In foot and mouth disease, blisters appear in mouth and on feet. Saliva oozes out of mouth in excess, there is soreness of mouth, appetite diminishes and there is high fever. It even causes death to cattles. There are certain bacterial, viral and fungal diseases of animals that are transmitted to human beings. So one should be careful to prevent and control such diseases. These are rabies, cow pox, encephalitis (viral), anthrax, tuberculosis and brucellosis (bacterial) and actinomycosis, aspergilosis and ring worm (fungal). Certain protozoan parasites (e.g., Entamoeba and Trypanos01l!a) also cause infection in man. For bacterial and viral diseases, vaccines have been developed and are available in the market. For controlling various types of diseases in cattles and domestic animals, veterinary hospitals are present in every district and town of the country.
I
Prevention of Animal Diseases I. Animal shelters should be well-cleaned and aerated. 2. Animals should get good food and clean drinking water. 3. Their regular bathing is also essential for preventing external parasites. If external parasites infest the animal, apply solution of insecticides. 4. Diseased animals should be kept separate. 5. Vaccination may be done against bacterial and viral diseases. 6. Prevent rats from entering animal shelters.
I
Meat Providing Livestocks
Goat, sheep and pig together supply about seventy per cent meat in India. Goat meat demand is more than sheep and pig meat. Sheep and goat also provide milk and wool. Their maintenance is also easy. Sheep do not need a good shelter. They can live in flocks under natural shades of trees and hills. Sheep eat a variety of plants including weeds. Indigenous breeds of sheep are Nellore and Mandya, and Dorset and Suffolk are exotic breeds. Indigenous breeds are famous for production of wool and exotic breeds for mutton. Their cross breeds gain 30 to 50 per cent more body weight. Hence, they are better for the production of mutton. Indigenous breeds of goat in our country are about twenty. These are Jamunapari, Himalayan, Bengal and Assam hill breed, Decanny and Osmanabadi, Kathiyabari, etc. Popular exotic breeds are Alpine, Toggenberg and Sannen. Goats' shelter should be dry, safe and secure from predators (e.g., wolves) and protected from too much heat and cold. Goats need fresh and clean fodder, hay ofleguminous crops and leaves of trees. A goat requires about 5 kg roughages (green and dry) and 250 g concentrates. Common diseases of sheep and goat are caused by bacteria and virus. Bacterial diseases are Black quarter, Brucellosis and Vibriosis. Sore mouth, goat pox and rinderpest are viral diseases. Nutritional deficiency disease also occur in goats. They also suffer from parasitic attack. Regular vaccination, cleaning and consultation with veterinary doctors are essential to prevent diseases.
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VK Biology IX
Table 3.15 Diseases of animals I
Animal
Animal diseases
I
I
I
IFoot and mouth
Bacterial Cattles (cow. buffalo, sheep) Tuberculosis Cattles (cow, buffalo, sheep) Rinderpest Cattles (cow, buffu.lo, sheep) Salmonellosis Poultry birds Fowl pox
I
Viral
,
-
Pox
IRanikhe~
.Fungal -
-
I
Aspergillosis
Bee Keeping Nector, a sweet viscous liquid secreted by flowers is suck by bees and converted to honey by the action of an enzyme-invertase. It is then stored in special cells of hives. This honey is of enormous use to man. It is a sweet viscous fluid, rich in sugars, minerals, vitamins, amino acids and enzymes. Honey has great nutritive value and medicinal value. It is an essential requirement for children as it is rich in iron and calcium and helps the body to grow. Honey is a source of sugar in confectionery items like pastries and cakes. Its medicinal uses are wide. It is a blood purifier and cures cough and cold. It also cures ulcers of throat, tongue, stomach and intestine. In addition, beehives are also a source of wax, propolis and bee venom. Wax is secreted by wax glands of worker bees and is utilised in the construction of hives. This wax is of great use to us. It is used in the manufacture of cosmetics, cold creams, shaving creams, lipsticks, nail polishes, candles, ointments, lubricants, etc. Propolis are another collection of bees from the plants used in repairing and fastening combs. Bee venom is used in the manufacture of certain Ayurvedic and Homeopathic medicines. Keeping all this in mind, bee keeping for obtaining honey and other useful materials has become an agricultural enterprise. The practice of bee keeping is called apiculture.
I
Fig. 3.22 Honey bee
Honey Bee Varieties Used for Bee Keeping
Both indigenous and exotic varieties of honey bees are used for commercial production of honey in India. 1. Indegenous Varieties of Honey Bees include, Apis cerana indica F. (Indian bee). Apis dorsata F. (Rock bee), Apis florae F. (Little bee). 2. Exotic Varieties of Honey Bees are Apis mellifera (European or Italian bee), Apis adamsoni (South African bee). The South African bee yields 100 kg per hive per year which is twelve times the Indian average of 4.5 kg per hive per year. The Italian bee yields an average of 50 to 200 kg of honey per hive per year. Italian bee (APis melli/era) is commonly domesticated in India to increase the yield of honey.
I
Colony of Bees
Honey bee is a social insect that lives in colonies and provides a very good example of division of labour and caste system. Different tasks are done by different groups of bees in the same colony. A colony may have 40,000 to 1,00,000 individuals. Individuals show polymorphism, i.e., individuals show a distinct form of variation in morphology. There are three castes-queen, drones and workers-individuals of each caste are morphologically distinct from those of others. Queen It is generally one in a colony and is the largest. The queen remains inside the hive and lays eggs. It lays up to 2,000 eggs everyday, both fertilised and unfertilised. It is fed on proteinaceous food like royal jelly.
.;'-- VK Biology IX
128
Improvement in Food Resources
Drones They emerge from the unfertilised eggs and are fertile males. They are stingless and medium sized. Their role is to mate with the queen, eat honey and remain inside the hives. They are driven away from the hives to save the honey. Workers They emerge from the fertilised eggs and are sterile females. They are the smallest in size but are the most active of all. They have pollen sacs, sting and wax glands and perform all domestic and field works. During the initial period of their life, they perform indoor duties like cleaning up the cells before the queen bee lays eggs in them. Then they build new combs and seal them with wax. In the later stage of life they do the outdoor activities like collection of nectars from flowers and store them in storage cells and convert them into honey by their enzyme actions. They also defend their colony from enemy by stinging it. They immediately die off after stinging. Apiculture and management of honey production is a fast growing cottage industry in India with about 5.75 lakh bee colonies working to produce honey at present. According to rough estimates, the total output of honey in India at present is about 5 million tonnes per annum. Tamil Nadu is the top honey producer {o"",""d b~ K,,-,a\a a"d Kan,atal,;.a. fm I:0mm,,-,c,a\ pYDduct\Dn Df 'uDnq, ap\a,\e:. are established. An apiary is a place where bee hives are kept to obtain honey and other bee products. Beehive A beehive is a special box of wooden chambers for laying eggs and honey collection. There are three types of artificial beehives used in India: • Langstroth
• Newton
• Jeolikote
While the Langstroth beehive is used in hilly regions the latter two are formed in plains. The quality and taste of honey depends upon the flora or orchards available in the near vicinity of the apiary. Apiaries are situated near mango groves, coconut trees, almond trees, apple trees, orchards of cashew nuts, guava trees and honey obtained from these apiaries taste accordingly. Almond honey of Kashmir tastes very good.
Fig. 323 BeehIVe
A suitable site of apiary should have abundance of flowers with a longer honey flow time (the total time during which bees collect nectar and pollens). It should receive sunlight during morning and evening and some shade during mid-day. Water should be available nearby.
I
Selection of Honey Bee Variety
The Italian bee, Apis melliferia, is most widely used for honey production in India. This bee yields an average of 50 to 20 kg of honey per hive per year.
I
Diseases and Enemies of Honey Bee
Honey bees are commonly infected by viruses, bacteria, fungi and protozoa. For example, the bacterium Bacillus apisceptio!ls infects blood of bee causing septicemia. Brood foul disease is caused by Schizomycetes (fungi). Nosema disease and Improvement in Food Resources
129
,.'
amoeba diseases are caused by protozoan pathogens Nosema apis and Vahlkampfla mellifira, respectively. Common pests/enemies of bees are wasps, wax moths and mites. Various birds such as king crows, blue tits, fly-catchers, chaffinch, green blue eater, sparrows, etc., use bee as their meal. Wasps are controlled manually (i.e., by destroying the wasp nests from the locality of apiary). Wax moth is controlled by exposing bees in bee hive to sun, by increasing temperature. Bee-eating birds are scared away by some device.
FORMATIVE ASSESSMENT FA 3.12: Word Box Topic: Fish production Directions: Complete the paragraph given below choosing the appropriate words from the word box in the space provided. catlas pomphret, mackerel and Bombay duck oysters bhetki and pearl spots rice crop mullets Mrigals and Common Carps composite fish culture system five or six Grass Carps The water source of the fish can be either sea water or fresh water, such as in rivers and ponds. Popular marine fish varieties include _ _________ and , . Marine fish are caught using many kinds of fishing nets [Tom fishing boats. Some marine fish of high economic value are also farmed which include finned fish and like , _________are also cultivated for the pearls they make. Fresh water resources include canals, ponds, reservoirs and rivers. Fish culture is sometimes done in combination with a , --------, so that fish are grown in the water in the paddy field. More intensive fish farming is done in . In such a system, a combination of _________ or fish species is used in a single fishpond. As a result, the food available in all the parts of the pond is used. As are surface feeders, feed in the middle-zone, and are bottom feeders, and feed on the weeds.
FA 3.13: True or False State whether the following statements are True or False.
r.
Jersey is an Indian breed of cow. 2. To enhance poultry production, cross breeding is done between Indian and exotic breeds for variety improvement. 3. To increase the production of fish, they can be cultured in marine and inland ecosystems. 4. Poultry farming is done to raise domestic fowls for egg production and chicken meat.
5. Most fish production in inland waterbody is capture fishing.
..
130
Improvement in Food Resources
6. One major problem with composite fish culture is that many of these fish breed only during monsoon. 7. The value or quality of honey depends upon the pasturage, or the flowers available to the bees for nectar and pollen collection.
FA 3.14: Match the Following: Match the terms in column I to their meanings in column II. Column I Column II (a) Catlas (i) Broiler (b) Rohus (ii) Surface feeders (c) MrigaJ (iii) Bottom feeders (d) Fish farming (iv) Milk-producing females (e) Bees used for commercial (v) Local breed of cattle honey production if) Oysters (vi) Aseel (g) Cattle used for tilling and carting (vii) Pearls (h) Indian breed of chicken (viii) Draught animals (i) Sahiwal and Red Sindhi (ix) Middle-zone feeders (J) Milch (x) Culture fishery (k) Chicken better food for obtaining meat (xi) Apis cerana indica, A dorsata, A florae
FA 3.15: Bead Necklaces Given below are outline structures of some 'Bead Necklaces' and a list ofcharacters placed in different categories. Each necklace is given a name that is actually the 'term' important for Food Production. You have to pick one character from each category to list the features of a group. In this way, you will 'string the beads' and the necklace will be complete when all the beads have been allotted characters from each category. Categories
•
A
B
C
D
E
For Milk and Draught labour
Layers and broilers
Fowl
Dwarf parent
Mullets and Bhetki
For egg production
Marine and fresh water varieties
monodon
Cheap
Dairy and
Apis
source of animal
draught animals
dorsO-la~
Large schools are located in open
Apis melliJera
and eeo-sounders;
and chicken meat
preferred for commercial chick
production
protein obtained
Peneaus
Lactation period is important while
Aseeland Leghorn
selecting the right breed Jersey, Red Sindhi
sea using satellites
Capture and
from water
culture methods
are also used For production
Local and Italian
honey
variety
Improvement in Food Resources
Bas indicus and Bos bubalis
Rock bee Value or quality of product depends and little bee upan pasturage 13l
VK Biology IX
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~ FARMING
E
A B
c
o
.~ FARMING
E
A
c
o
~ PRODUCTION
E
B
132
c
o Improvement in Food Resources
rBEE"\ KEEPING
E
A B
c
o
FA 3.16: Group Discussion Divide the class in small groups. Discuss animal husbandry and discuss following questions in your group. I. Name the method commonly used for improving cattle breeds and also state why it is used. 2. Name any two Indian breeds of (i) cows and (ii) buffaloes. 3. Define animal husbandry. 4. How is cross breeding useful in cattle?
SUMMARY I Human beings use plants and animals as food. I Plants are autotrophs, i.e., they manufacture their food as starch (carbohydrate). I Animals and human beings are heterotrophs, i.e., feed on plants and animals. I Plants get carbon and oxygen from air, hydrogen from water and rest from the soil to
I I
I
I I I
manufacture food through a process called photosynthesis. Man is constantly trying to improve the quality and increase the quantity of food to support a growing population. Improvement in yield of crops should be done in three stages: -crop variety improved -crop production management -crop protection management While the first stage includes selection of an improved variety of seeds through hybridisation and genetic engineer, the second stage deals with nurturing of crops through nutrient management, cropping pattern, irrigation, etc. The third stage is protection of the harvest. Manures are natural bulky organic matter, e.g., farmyard manure (FYM), compost, green manure and vermicompost. Manures restore the soil texture for water retention and soil aeration. Manures provide food for soil organisms, like bacteria and fungi. They decompose organic matter and provide nutrients to plants.
Improvement in Food Resources
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VK Biology IX
---:,.
I FYM is a decomposed mixture of cattle's excreta, roughage or unused fodder. It I I I I
I I
I I
I I I I I I
I
I I
134
provides nitrogen, phosphorus and potassium to the crop. Compost is vegetable and animal refuse of town area, like animal excreta, faecal matter of humans and sewage waste. It is decomposed by microorganisms. It contains the same nutrients as that of FYM. Green manuring is growing of leguminous and non-leguminous crops in the field, ploughing (before flowering) and mixing with the soil. These are decomposed in the soil by microorganisms. This is done before rains. Leguminous plants provide nitrogen to the soil. Fertilisers are chemicals produced by the factories. These are inorganic, e.g., ammonium sulphate and organic like urea. Fertilisers are nitrogenous (urea, ammonium sulphate, sodium and ammonium nitrate), phosphatic (superphosphates and dicalcium phosphate), potassic (potassium chloride, sulphate and nitrate) and complex like nitrophosphate, ammonium phosphate, urea ammonium phosphate providing two or more nutrients. Biofertilisers add nitrogen to the soil. These are cyanobacteria, phosphate solubilising microorganisms, Rhizobium, blue-green algae, and mycorrhiza (fungi lives in roots of higher plants). Water is very essential for crop production. Its judicious use increases the crop yield. Where water is not available for irrigation, crop yield is low. Crop production entirely depends on rain water. Insufficient rain or no rain creates drought condition. Crops dry off. Crop protection is to protect the crop from pests, i.e., insects, fungi, bacteria, viruses, worms, rodents, etc. Insects are killed by insecticides, fungi are destroyed by fungicides. Chemicals used to kill pests (e.g., weeds, fungi, insects, mites and rodents) are called pesticides. Pesticides are either sprayed or dusted over crops, or mixed with seeds and soil. For preventive measures for the crops- resistant varieties of crop plants, crop rotation and multiple cropping and summer ploughing are used. Contact insecticides are malathion, lindane and thiodon. They are sprayed on stem and leaf cutting and boring insects. Systemic insecticides are dimethoate and metasystox. These are also sprayed. These are absorbed by the plants. When sap sucking insects feed on plants they are killed. Sucking insecticides are aphids (Aphis), Pyrilla (leaf hoppers), plant bugs like red cotton bug (Dysdercus ). Plant borers are sugarcane borers, chick pea pod borers, cotton boll weevil and grain weevil. Weeds are small sized unwanted plants growing along with cultivated crops in the field. They suppress the growth of the crop plants and use nutrients from the soil. Examples of weeds are motha (nut grass), jangJi jowar (wild sorghum), chau/ai, sathi, jangJi jar, bathua and hirankhuri. Chemicals used for destroying weeds are 2, 4-dichlorophenoxy acetic acid, atrazine, f1uchoralin, etc. Biological control is done by cochineal insects for Opuntia; grass carp (fish) is used to control aquatic weeds. Pests of stored grains are pulse beetle damage grams; rice weevil damage rice; wheat weevil, grain and flour moth of rice, wheat, maize, etc., rust red flour beetle, rice moth and lesser grain borer. Their adults or larva (grub) or both damage the grains and their flour. Grains (rice, wheat, etc.) are stored in gunny bags and FCI silos. For storage of grains, temperature of storage houses should not be more than 30·C and moisture content should be 14% or less by weight. More humidity causes development of fungus. Improvement in Food Resources
•
Storage places should be cleaned, free from cracks or holes in the walls, etc., gunny bags should be stitched properly after filling grains and if needed the place should be fummigated.
•
Spray insecticides over grain-filled gunny bags. Gammaxene or benzene hexachloride wettable powder (BHC WP), pyrethrum and malathion are some insecticides to name.
•
Fumigants are ethylene dibromide (EDB), ethylene dichloride plus carbon tetrachloride (EDCT) in liquid form; aluminium phosphide (AlP) in solid state and methyl bromide in gaseous state.
•
Animal husbandry deals with the breeding, feeding, rearing, shelter and caring of domestic animals and meat and egg giving animals, etc.
•
Objective of animal husbandry is to improve cattle and live stock breeds to get higher yields of milk, meat, eggs, wool, etc.
•
Improved Indian breeds of cows are Red Sind hi and Tharparkar of Andhra Pradesh, Gir of Gujarat, Sahiwal of Punjab and Haryana.
•
Exotic breeds of cows are imported breeds brought from European countries. These are high milk yielding cows, e.g., Holstein, Swiss, Jersey and Friesian.
•
Improved cow-breeds developed by NDRI, Kamal are Karan Swiss (Swiss X Sahiwal), Karan Friesian (Tharparkar X Holstein Friesian) and Frieswall (Sahiwal X Holstein Friesian).
•
Buffalo breeds are Murrah of Punjab and Haryana, Mehsana and Surti of Gujarat.
•
Sheep are reared for milk, meat, wool and hide. Their important breeds are Gaddi and Rampuri of Himalayan region, Bikaneri, Marwari and Deccani.
•
Important breeds of goats are Kashmiri, Gaddi and Surti
•
Poultry breeds are White Leghorn, Minorcha and Rhode Island Red. They lay about 200 to 300 eggs per year.
•
Desi or indigenous breeds are Brahma, Chittagong, Aseel and Basara, etc., which lay only 60 to 75 eggs per year. Their eggs are smaller in size. But these are good sitters.
•
Improved poultry cross breeds are B-n, HH266 and ILS-80.
•
Fish farming is called pisciculture. Fish is a good source of meat. Fish liver oil is rich in vitamin A and D and is an unsaturated oil.
•
Marine fishes are salmon, sharks, etc.
•
Fresh water fishes are rohu, catla, mrigal. These are called major carps. Other fish are Wallago (malli), Mystus (singhara), C1arias (mangur) and singhi.
•
Artificial fish breeding is done in Indian Veterinary Research Institute, Izatnagar, Bareilly.
•
Fresh water fish are cultured in hatcheries, bunds, rivers and ponds, etc.
•
Breeding of animals (cows and buffaloes) is also done by artificial means, i.e., by artificial insemination. It is the introduction of semen of good variety bull into the female reproductive tract by the means of a special instrument.
•
Artificial Insemination is better than Natural Mating.
•
Operation flood (white revolution) is to increase milk yield of milch animals. Dr. Kurien is the father of white revolution. He is an architect of India's modern dairy industry.
•
NDDB is National Dairy Development Board.
•
VHS is viral haemorrhagic septicemia, a disease of fish.
•
IPN is infectious pancreatic necrosis, a disease of fish.
• •
NDRI is National Dairy Research Institute, Kamal. Pasteurisation is a process to kill microorganisms of milk which cause spoilage. Milk is heated at a high temperature and then brought down to room temperature.
Improvement in Food Resources
FA 5. Multiple Choice Questions Select the right choice. 1. Find out the wrong statement from the following (a) White revolution is meant for increase in milk production. (b) Blue revolution is meant for increase in fish production (c) Increasing food production without compromising with environmental quality is called as sustainable agriculture. (d) None of the above 2. To solve the food problem of the country which among the following is necessary? (a) Increased production and storage offood grains (b) Easy access of people to the food grain (c) People should have money to purchase the grains (d) All of the above 3. Find out the correct sentences (i) H ybridisation means crossing between genetically dissimilar plants (ii) Cross between two varieties is called as inter specific hybridization (iii) Introducing genes of desired character into a plant gives genetically modified crop (iv) Cross between plants of two species is called as inter varietal hybridization (a) (i) and (ii) (b) (ii) and (iv) (c) (ii) and (iii) (d) (iii) and (iv) 4. Find out the correct sentence about manure (i) Manure contains large quantities of organic matter and small quantities of nutrients. (ii) It increases the water holding capacity of sandy soil. (iii) It helps in draining out of excess of water from clayey soil. (iv) It excessive use pollutes environment because it is made of animal excretory waste. (a) (i) and (iii) (b) (i) and (ii) (c) (ii) and (iii) (d) (iii) and (iv) 5. Cattle husbandry is done for the following purposes (i) Milk production (ii) Agricultural work (iii) Meat production (iv) Egg production (a) (i), (ii) and (iii) (b) (ii), (iii) and (iv) (c) (iii) and (iv) (d) (i) and (iv) 6. Which of the following are Indian cattle? (i) Bos indicus (ii) Bos domestica (iii) Bos bubalis (iv) Bos vulgaris (a) (i) and (iii) (b) (i) and (ii) (c) (ii) and (iii) (d) (iii) and (iv) 7. Which of the following are exotic breeds? (i) Brawn (ii) (iii) Brown Swiss (iv) (a) (i) and (iii) (b) (c) (i) and (iv) (d)
Jersey Jersey Swiss (ii) and (iii) (ii) and (iv)
8. Poultry farming is undertaken to raise following (i) Egg production (ii) Feather production (iii) Chicken meat (iv) Milk production (a) (i) and (iii) (b) (i) and (ii) (c) (ii) and (iii) (d) (iii) and (iv) miii'iJiiil138
Improvement in Food Resources
9. Poultry fowl are susceptible to the following pathogens (a) Viruses (b) Bacteria (c) Fungi (d) All of the above
::ailed
10. Which one of the following fishes is a surface feeder? (a) Rohus (b) Mrigals (c) Common carps (d) Cadas 11. Animal husbandry is the scientific management of (i) animal breeding (ii) culture of animals (iii) animal livestock (iv) rearing of animals (a) (i), (ii) and (iii) (b) (ii), (iii) and (iv) (c) (i), (ii) and (iv) (d) (i), (iii) and (iv) 12. Which one of the following nutrients is not available in fertilizers? (a) Nitrogen (b) Phosphorus (c) Iron (d) Potassium 13. Preventive and control measures adopted for the storage of grains include (a) strict cleaning (b) proper disjoining (c) fumigation (d) all ofthe above Answers 1. (d)
2. (d)
9. (d)
10. (d)
3. (a) 11. (d)
4. (b)
5. (a)
12. (c)
13. (d)
6. (a)
7. (b)
8. (a)
FA 6. Flow-chart Worksheet Instructions: Identify the missing steps/processes/examples in the flowchart given below and complete it using the appropriate words.
• •
•
Improvement in
Crop _ _---,Improvement
Crop Variety Improvement
Crop Protection Management Protection in the field against Weeds, Insects and Pests
Yield Improved Quality and Abiotic Ressistanc Change in
Nutrient Management
and Macronutrients
Irrigation Wells, Canals, River lift systems and tanks
Protection during Storage against Biotic and Abiotic Factors
Manures and Wider Adaptability
Mixed Cropping
Desirable
Methods of Crop Variety Improvement 1. Hybridisation 2. Genetic manipulation (GMO)
Improvement in Food Resources
Crop Rotation
139
FA 7. Worksheet Instructions: • •
Given below are five pictures related to Food Production. Provide a title for these pictures from the terms given here, in the space provided. Mariculture • •
Multiple Cropping
Composite Fish Culture
Poultry
Livestock Farming
State one desirable characteristic or advantage of each of these. These may be written on a separate sheet.
t
~~~~~~~~~. .N
-
~
~~U®H~II"\.y'II "
f'
~
.;
ttttt ' .'~:"
4.
_ (Rearing varieties of Hen)
~~
-"C-
1.
_
(Growing crops on the same land)
3.
~
~,-
5.
_
_
(Growing Catla, Rohu, Grasscarp and mrigal together)
(Growing Peneous monodonThe prawn found in sea)
FA 8. Paper Pen Test 1. Answer the following question. (a) What is GM crop? Name anyone crop which is grown in India. (b) Why is organic matter important for crop production? (e) Define the terms hybridisation and photoperiod. (d) Cultivation practices and crop yield are related to environmental conditions. Explain. (e) Discuss the role of hybridisation in crop improvement. If) Why bee keeping should be done in good pasturage) 2. Fill in the blanks. (a) Kharif crops are cultivated from (b) Rabi crops are cultivated from (e) Most of the food comes from ~.~
140
to to
_ _
and animal husbandry. Improvement in Food Resources
(d) Milk production can be increased by increasing (e) Pigeon pea is a good source of
period.
_
3. True or False. (a) Mullets are marine fish farmed in sea water. (b) Poultry production involved egg production and broiler production for poultry meat. (c) The growing of different crops on a piece of land in pre-planned succession is called inter-cropping. (d) Organic farming is a fanning system with maximum or excessive use of chemicals as fertilisers, herbicides, pesticides, etc. and with minimum input of organic manures and recycled farm wastes. 4. Match the following. Column I
Column II
The value or quality of honey depends upon
(i) Many of the fishes breed only during
Problem with composite fish culture
(ii) Pasturage or the flowers available to the
(c)
Broiler chicken are fed vitamin like
bees for nectar and pollen collection. (iii) Milk and draught labour.
(d)
Cattle husbandry is done for two purposes (iv) Vitamins A and K.
(e)
Food stuff provide proteins
(a)
(b)
monsoon.
(v) Soyabean, ground nut, seasame, castor,
mustard, linsead and sunflower.
if)
Food stuff provide fats
(vi) Gram, pea, black gram, green gram,
pigeon pea, and lentil. 5. Multiple Choice Questions (a) Which one is an oil yielding plant among the following? (i) Lentil (iii) Cauliflower
(ii) Sunflower (iv) Hibiscus
(b) Weeds affect the crop plants by (i) killing of plants in field before they grow. (ii) dominating the plants to grow. (iii) competing for various resources of crops (plants) causing low availability of nutrients. (iv) all of these.
(c) Which of the following is an Italian bee variety? (i) Apis Cerana indica (iii) Apis dorsata
(ii) Apis mellifera (iv) Apis florae
(d) Which of the following combinations are most suitable for composite fish culture? (i) Surface feeders and bottom feeders
(ii) Surface feeders, middle zone feeders and bottom feeders (iii) Middle zone feeders and bottom feeders (iv) Surface feeders only
(e) Which of the following is not a source of carbohydrate? (i) Rice (ii) Millets (iii) Sorghum
Improvement in Food Resources
(iv) Gram
141
SUMMATlVE ASSESSMENT A. Textbook Questions with their Answers 1. What do we get from cereals, pulses, fruits and vegetables? Ans. Cereals like wheat and rice provide us carbohydrates for fulfilling the body's energy requirement. Pulses like gram and peas provide us with proteins. Fruits and vegetables provide us with a range of vitamins and minerals in addition to some proteins, carbohydrates and fats. 2. How do biotic and abiotic factors affect crop production? Ans. Biotic factors like diseases, insects and nematodes, and abiotic factors like drought, salinity, waterlogging, heat, cold and frost have a negative impact on crop production, i.e., the crop yield decreases due to these factors. 3. What are the desirable agronomic characteristics for crop improvements? Ans. For fodder crops, height and profuse branching are desirable characteristics. For cereal crops, dwarfness is desired, so that less nutrients are consumed by the crops. In this way, developing varieties of desired agronomic characters give higher productivity, i.e., higher yield. 4. What are macronutrients and why are they so called? Ans. Sixteen nutrients are essential for plants, out of which thirteen are supplied by the soil. Among these, six are required in large quantities. As these are required in large quantities, they are called macronutrients. They are: (1) niu'ogen (2) phosphorus (3) potassium (4) calcium (5) magnesium and (6) sulphur. 5. Where do plants get nutrients from? Ans. Plants get nutrients from air, water and soil. There are basically sixteen nutrients that are essential for plants. Of these, carbon dioxide and oxygen are obtained from air, hydrogen from water and the rest of the thirteen nutrients are supplied by the soil. 6. Compare the use of manures and fertilisers in maintaining soil fertility. Ans. Manures are rich in organic matter but are poor in nutrients. For this reason, the cultivated field supplied with only manures may suffer from deficiency of nutrients which will automatically result in poor yield; whereas fertilisers are inorganic compounds and fulfil nutrient requirement of soil. So, the field which is supplied with fertilisers only may face drainage problem and waterlogging due to lack of organic matter in the soil which will bring harm to the crop and the yield. Moreover, the use offertilisers over long periods of time can destroy the soil structure by killing the soil microorganisms that recycle nutrients in the soil. 7. Which of the following conditions will give the most benefits? Why? (a) Farmers use high-quality seeds, do not adopt irrigation or use fertilisers. (b) Farmers use ordinary seeds, adopt irrigation and use fertilisers. (e) Farmers use quality seeds, adopt irrigation and use fertilisers and crop protection measures.
Ans. Conditions given in (e) will give the most benefits because: (a) Farmer will benefit by using quality seeds. (b) Proper irrigation will overcome drought or flood situations. (e) Fertilisers will provide nutrients and there will be higher yield. For most benefits, every aspect of agriculture should be taken care of. 8. Why should preventive measures and biological control methods be preferred for protecting crops? Ans. Preventive measures and biological control methods are preferred because: (a) They are simple. (b) They are more economic. (e) They minimise pollution without affecting the soil quality. 142
Improvement in Food Resources
9. What factors may be responsible for losses of grains during storage? Ans. The following factors are responsible: (a) Abiotic factors like inappropriate moisture and temperature. (b) Biotic factors like insects, rodents, birds, mites and microorganisms. 10. Which method is commonly used for improving cattle breed and why? Ans. The commonly used method for improving cattle breed is cross-breeding two cattles having the desired qualilties. For e.g., by crossing Brown Swiss having long lactation periods is crossed with Red Sindhi having disease resistance to get a breed having both qualities. 11. Discuss the implications of the following statement: "It is interesting to note that poultry is India's most efficient converter of low fibre food stuff (which is unfit for human consumption) into highly nutritious animal protein food." Ans. The feed consumed by poultry birds is fibrous and cheap. Moreover, it is formulated using agricultural by-product. In this way, the product not used by human population are converted into chicken meat and the eggs produced by poultry birds, which are highly nutritious and are used by humans. 12. What management practices are common in dairy and poultry farming? Ans. (a) Shelter: In both dairy and poultry farming, should be, well-designed, airy and hygienic shelter. (b) Feeding: Healthy feed is provided to both dairy animals and poultry birds to get good yield. (c) Caring for animal health: Both animals and birds must be protected from various diseases. 13. What are the differences between broilers and layers and in their management? Ans. The broiler is a poultry bird specially groomed for obtaining meat and layer is the egglaying poultry bird. As per the purpose for which they are raised the housing, nutritional and environmental requirements of broilers are somewhat different from those of the layers. The daily food requirement ration for broilers is protein-rich with adequate fat and high amount of vitamin A and K; whereas the layers require enough space and proper lighting. 14. How are fish obtained? Ans. Fish are obtained by either from the natural resources which is called capture fishing or by fish farming which is called culture fishery. 15. What are the advantages of composite fish culture? Ans. The advantages of composite fish culture are: (a) The species are selected in such a way that they do not compete for food among themselves, and have different types of food habits. Due to this, the food available in all parts of the pond is used. For example, Catlas are surface feeders, Rohu feed in the middle-zone of the pond, while Mrigals and common carps are bottom feeders. Also, Grass Carps feed on the weeds. (b) All these species together use all the food in the pond without competing with each other. (c) This increases the fish yield from the pond. 16. What are the desirable characteristics of a bee for honey production? Ans. Desirable characteristics of a bee for bee-keeping are: (a) Good honey collection capacity. (b) Ability to protect itself from enemies. (c) Prolific queen production with less swarming. 17. What is pasturage and how is it related to honey production? Ans. The flora/crops found around an apiary to collect honey and pollen grains is called pasturage. Pasturage flora of honey bee includes Mango, Coconut, Almond, Apple, Tamarind, Sisam, Mahua, etc. Improvement in Food Resources
143
18. Ans.
19. Ans. 20. Ans.
The quality and taste of honey depends upon the flora/pasturage around the apiary from which bees collect the nectar and pollens. For instance, the Kashmir region having almond plant pasturage around apiary produces almond honey which is good in quality, taste as well as aroma. Explain anyone method of crop production which ensures high yield. Use of manures and fertilisers ensure high yield. Manures are important source of nutrients whereas fertilisers provide nitrogen, phosphorus and potassium to the crops. For the proper growth of crops and for high yield, all the nutrients, both macronutrients and micronutrients must be provided to the crops. Manures add humus to the soil which makes the soil very fertile. Why are manures and fertilisers used in the fields? Manures and fertilisers are used in the fields to make the soil fertile by improving the soil texture and nutrient content of the soil. What are the advantages of intercropping and crop rotation? Advantages of intercropping: (a) In intercropping, two or more crops are simultaneously grown on the same field in a definite row pattern-a few rows of one crop and adjoining to that a few rows of another crop. This practice reduces intraspecific competition. (b) This ensures that both crops can give better yield. (e) There is maximum utilisation of nutrients and minimum spread of pests. Advantages of crop rotation: (a) It makes the soil fertile and helps in the increase of crop yield. (b) It also decreases the demand of nitrogenous fertilisers as leguminous plants grown during crop rotation fix the atmospheric nitrogen. (e) The selected rotation of crops also helps in pest control, as pests do not find their favourite crop in the next season and it becomes difficult for them to survive there.
21. What is genetic manipUlation? How is it useful in agricultural practices? Ans. Incorporating desirable characters by hybridisation, mutation, DNA recombination, etc., is called genetic manipulation. By genetic manipulation, we get improved varieties of seeds having desired characters like pest and disease resistance and high yield. Their seeds not only give higher yield but also reduce the input cost. 22. How do stored grain losses occur? Ans. There are two types of factors responsible for losses during storage of grains. These are: (a) Biotic factors such as insects, rodents, mites and bacteria. (b) Abiotic factors such as temperature, moisture content and humidity. 23. How do good animal husbandry practices benefit farmers? Ans. By animal husbandry, we mean scientific management of farm animals. Good animal husbandry practices benefit the farmers in the following ways: (a) Improvement of breeds of the domesticated animals. (b) Reduction of the input cost. 24. What are the benefits of cattle farming? Ans. The main benefits of cattle farming are: (a) Wet milk from cattle and other milk products like butter, cheese, etc. (b) Bullock labour is used for agricultural practices such as tilling, irrigation and carting. 25. For increasing production, what is common in poultry, fisheries and bee-keeping? Ans. Selection of improved varieties, housing, rearing, sanitation, disease control and management offood.
144
Improvement in Food Resources
26. How do you differentiate between capture fishing, mariculture and aquaculture? Ans. Aquaculture Capture fishing Mariculture (a)
I
It is the process of obtaining I t is a practice of culture of It is the production of fish from fish from the natural marine fish varieties in the open freshwater resources like canals, resources like ponds, canals, sea. ponds, reservoirs, rIvers and rivers, etc. brackish water resources like estuaries and lagoons.
in fishing, (b) In capture fishing, fish can In mariculture. satellites and Like capture be located easily and then echo-sounders are used for aquaculture also the fish can be caught using fishing nets. locating fish. Then they are located easily and are caught caught USLng man}' kinds of using simple fishing nets. fishing nets from the fishing boats.
HOTS (Higher Order Thinking Skills) 1. Why is use of excess fertiliser determental for environment? Ans. Fertilisers observing pre and post-application precautions for their compelte utilisation. Fertilisers get washed away due to excessive irrigation and are not fully absorbed by the plams. This excess fertiliser then leads to water pollution. Conditions use of fertilisers in an are can destroy soil fertility because the organic matter in the soil is not replenished and micro-organisms in the soil are harmed by the fertilisers used. 2. List out some useful traits in improved crop? Ans. Some useful traits in improved crops are: (i) Higher yield of crop (ii) Improved quality of crop (iii) Biotic and abiotic resistance (iv) Change in maturity duration (v) Wider adaptability and (vi) Desiratble agronomic characteristics. 3. Arrange these statements in correct sequence of preparation of green manure. (a) Green plants are decomposed in soil (b) Green plants are cultivated for preparating manure or crop plant parts are used. (c) Plants are ploughed and mixed in soil. (d) After decomposition, it becomes green manure. Ans. b )C ) a ) d. 4. Discuss why pesticides are used in very accuracy concentration and in very appropriate manner? Ans. Pesticides include herbicides, insecticides and fungicides which are sprayed on crop plants or used for treating seeds and soil. However, excessive use of these chemicals creates problems, since they can be poisonous to many plam and animal species and cause environmental pollution.
Improvement in Food Resources
145
VK Biology IX
EXERCISES (1 mark)
Very Short Answer Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
Name any common weed found in a field. Define a weed. Name two fertilisers. Name one animal storage pests. Name the nitrogenous fertilisers. Name one insecticide. Write the full form ofEDCT Name a green manure. Define venni-composting. Name two varieties ofIndian fish. Mention one each of high milk-yielding varieties of cow and buffalo. Write the full form of NDRI. What is the role of roughage in cattle feed' Name four animals which provide us food. Name any two Indian breeds of (i) cows, and (ii) buffaloes. Mention the percentage of protein content in milk, egg and fish. Write two high yielding varieties of poultry. Name any two animal diseases carried by bacteria and viruses. How are goats and sheep useful to us?
Short Answer Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.
(2,3 marks)
Write three sorts of precautions for handling pesticides. Name two common weeds found in agricultural fields. Mention their control. Name the factors responsible for grain loss during the storage of grains. What are pesticides? Name one pesticide. Mention the improved cross-breeds of cow. What do you mean by 'Operation Flood" Write any two responsible factors. Define animal husbandry. Mention the salient features of a good shelter. What is Silver Revolution? What are the major sources of our food' Write two infectious diseases, each of cow, poultry and fish. Define artificial insemination. Give three uses of animal husbandry. Mention the names of animal products which are used as food. How is cross-breeding useful in cattle? Mention three characteristics of a good animal shelter.
Long Answer Questions
(5 marks)
1. Name some improved storage structures for grain. Explain how grain is protected in these structures.
2. Discuss various measures for safe storage of grains.
..
VK Biology IX 146
Improvement in Food Resources
3. Name one disease each of rice, wheat, mustard and sugarcane and suggest their control measures. 4. Name two insect pests each of rice, mustard and sugarcane and suggest their control measures. 5. Define manures. What are the different manures and how do they affect the soil? 6. What are fertilisers? Classify fertilisers with suitable examples. 7. Define weeding. What tools are used for weeding?
8. What is green manuring? Give suitable examples for green manures. 9. 10. 11. 12.
13. 14. 15. 16.
''\That is a fertiliser? How is it different from manure? What are weeds? How are weeds controlled? How are agricultural pests harmful? What are crop pests? Suggest preventive measures to control pests. Describe various measures for controlling insect pests in crops. What are egg laying animals? Write the exotic breeds of poultry hen. How would you protect the animals from various diseases? How can we increase milk production in buffaloes and cows? Give names of improved breeds of cow and buffalo.
17. What measures have been taken to improve the production of food from animal sources in our country?
18. Milk production is meagre in India though there is a large population of cattle here. Why? 19. Mention few measures for prevention of diseases in the animals. 20. Briefly mention the advantages of artificial insemination. How is it done? 21. Name the different breeds of poultry bird. What is poultry farming?
Practical-based Multiple Choice Questions 1. Some food samples and their adulterants are given as follows I. Ghee (i) Orange dye II. Milk (ii) Tamarind seeds III. Coffee (iii) Starch IV. Red Chilly
(iv) Vanaspati
Four sequences of food samples and their correct adulterants are proposed from the above columns. Which one of the following sequence is correct? (a) I - (i), II, (ii), III - (iii), IV - (iv) (b) I-(iv), II - (iii), III-(ii), IV - (i) (c) 1- (iv), II- (iii), III-(i), IV - (ii) (d) I - (iii), II - (iv), III- (i), IV - (ii) 2. A Biology lab assistant was asked to prepare Iodine solution for starch test. He tried making the solution by mixing different chemicals in various ratios. Can you pick up the right combination from the following sets? (a) 2 g of Potassium Iodate in 100 mL distilled water (b) I g ofIodine in 100 mL distilled water (c) 1 g of Potassium Iodate + I g ofIodine ih lOa mL distilled water (d) 2 g of Potassium Iodide + I g oflodine in lOa mL distilled water 3. Excess of glucose present in blood is converted into glycogen in the presence of insulin hormone. Glycogen is stored in (a) muscles only (b) liver only (c) both a and
b
Improvement in Food Resources
(d) adi pocytes
147
VK Biology IX
4. Four students, studying biochemistry for the first time, decided to perform the confirmatory test for the presence of starch on potato slices. Since they were not sure of the chemical which could give the blue black colour with starch, they tried their hands with different types. Only one of them gave the correct result which can be identified as (a) fluorine (h) chlorine (c) iodine (d) bromine 5. Match the pair correctly. I. Glucose (i) Cane sugar II. Sucrose (ii) Apple III. Fructose (iii) Milk (iv) Blood sugar Iv. Lactose (a) I - (iv), II - (i), III - (ii), IV-(iii) (h) I - (i), II - (ii), III - (iv), IV - (iii) (c) I - (iv), II - (iii), III - (ii), IV -(i) (d) I - (ii), II-(i), III - (iii), IV - (iv) 6. An experiment was performed in Class IX to demonstrate the effect of denature agents on enzymes by taking different chemicals in 5mL starch solution. 15 minutes later, the tubes were tasted for the presence of starch with the help oflodine. One ofthe tubes did not give the blue black colour in the test tube because
5 mL starch solution + 1 mL Hel + 1 mL ptylin
(A)
5 mL starch solution + 1 mL alcohol + 1 mL ptylin
5 mL starch solution + 1 mL ptylin
(B)
(C)
5 mL starch solution + 1 mL water
(D)
(a) tube A as ptyalin was denatured (h) tube B as starch was destroyed with alcohol
(c) tube C as ptyalin changed starch into maltose (d) tube D as starch solution was diluted by adding water
7. Which of the following chemical is used to observe the presence of starch in the food extract? (a) 12 solution (Iodine) (h) Cone. HCl (c) Benedict's reagent (d) None of these 8. Substance 'X' was added to a test tube containing water and grounded arhar dal to test the presence of metanil yellow. The colour of solution changed to pink. Identify 'X'. (a) Hp (h) l\aOH (c) H 2C0 3 (d) HCl 9. A student added only two drops of iodine to a rice extract in test tube A. Another student added a little rice extract to iodine solution in test tube B. They would then observe (a) a change of colour to blue black in test tube A but not in test tube B (b) a change of colour to blue black in test tube B but not in test tube A
VK Biology IX
148
Improvement in Food Resources
(e) a change of colour to blue black in Doth test tubes A and B
(d) no change of colour in any test tube
10. Paul was rushing with a bottle of tincture iodine. Some iodine solution splashed on his yellow coloured cotton shirt and also on the white table cloth. The stain on the table cloth . was yellowish brown while that on his shirt was blue black. The most plausible scientific reason for this is that the (a) Shirt was dyed with metanil yellow (b) Shirt was starched after washing (e) Table cloth was starched but not the shirt (d) Shirt had absorbed sweat
II. Four samples of arhar dal (tuvar dal) were taken in four test tubes with some water in each and labelled P, Q, Rand S. A few drops of the following were added to these test tubes: water to test tube P, HCI to test tube Q, NaOH to test tube R and alcohol to test tube S. We would be able to confirm adulteration of the dal with metanil yellow in test tubes (a) P and Q (b) Qand R (e) Rand S
(d) Sand P
12. The teacher asked the student to correctly record results of the experiment done to detect presence of metanil yellow in the adulterated arhardal (tuvar dal) sample that was provided to them. S.No.
Procedure
A
5g da! + 5 g metani! yellow
Dal turns yellow
Metani! yellow present
B
5 g dal + 5 mL'water + 2 drops ofHCI
Solution turns pink
Metani! yellow present the sample
C
5 g dal + 5 mL water + pinch of metanil yellow
,.vater turns yellow
Metanil yellow present
D
5 g dal + 5 mL water + 2 drops of HC[
Metanil yellow present
Water turns yellow and then pink
Observation
Inference
111
The correct recording of the experiment is done in table (a) A (b) B (e) C
(d) D
13. On the laboratory table were placed four watch glasses with labels A, B, C and D. Watch glass "A" had chalk powder, "B" had sago powder, "C" had common salt and "D" had powdered sugar. On adding two drops of iodine to the content of each watch glass, the one turning blue black will be (a) A (b) B (e) C (d) D 14. Seema bought arhar dal (tuar dal) from the market. On adding water to the dal the water became yellow in colour. She took a sample of this yellow water to the laboratory and added a few drops ofHCI. The sample became pink. This confirmed that the adulterant added to the dal was (a) turmeric (b) metani! yellow (e) potassium dichromate (d) yellow dye
15. To observe starch granules in potato under a microscope, freshly cut surface of potato was pressed on a slide. The stain that will show starch granules clearly is (a) methylene blue (b) iodine (e) safran in (d) eosin 1-_t-...,;;lm;;:p;:.ro:.;v.:.;em;:.e;:.n.:.;li;:.n;:.Fo:.;O.:.;d;:.Re;;;so.:.;u;;,;rc;;;es=--
;:.[;:.4.:....9 liilii.:iil~;ii;l,t_---.
16. A very fast driver of a motorcycle met with an accident that resulted in heavy bleeding. As soon as he was rushed to the hospital they put him on intravenous 5% dextrose sugar. What is the other name of this sugar that is the instant source of energy? (a) Fructose (b) Glucose (e) Sucrose (d) Lactose
17. Identify the plant from the following that is not a pulse. (a) Mustard (b) Pea (e) Groundnut (d) Blackgram 18. An infant suffering from PEM disorder, Kwashiorkor was advised to have protein rich milk prepared from one ofthe legumes. Identify the source. (a) Groundnut (b) Arhar dal (e) Moong dal (d) Soyabeen 19. Which one does not correctly provide us starch grains found in the specific food stuff? (a) Potato (b) Banana (e) Wheat (d) Rice
20. Which is the most abundant carbohydrate found on earth? (a) Starch (b) Glycogen (e) Chitin (d) Cellulose 21. From the following carbohydrates, find out the one, that is insoluble in water. (a) Starch (b) Glucose (e) Fructose (d) Insulin 22. In slimming centres like VLCC, obese patients are advised not to have excess of certain nutrients but the restriction is not imposed on patients for one type of carbohydrates. Identify it. (a) Fats (b) Starch (e) Sucrose (d) Cellulose 23. A class IV student was having veg biryani during the break. A senior scolded him. Scared of his senior, he immediately ran to his elder brother who was a class XI student and was performing an experiment in chemistry lab with Iodine solution and collided with his elder bother, The solution spilled on biryani and changed its colour to blue black because (a) biryani is made from wheat which has starch in it (b) biryani is made from rice which has starch in it (e) biryani is made from pulses which has starch in it (d) iodine is already having blue black 24. Which of the following statements is incorrect? (a) A 40 years old gardener should be given lots of carbohydrate (b) A 5 year old child should be given lot of proteins and carbohydrates (e) A pregnant mother should be given lot of fats to get energy (d) A sick person should be given soft diet having proteins vitamins & minerals 25. Four students of Central School, Noida were provided with adulterated pulses to test the presence of metanil yellow. They all added 5mL of water to 5g of pulses but forgot the name of the acid that gives magenta colour with the adulterant. Sanjeevani, Shreya, Alka and Chitra added few drops of cone. , cone. , cone. HCI and respectively. Who according to you had added the right acid? (b) Shreya (a) Sanjeevani (d) Chitra (e) Alka
0.'
VK Biology IX
150
Improvement in Food Resources
26. Observe the following tubes carefully.
5 mL sugarcane juice + 2 mL fehllng (A) and fehling (8)
5 mL apple juice
5 mL grape juice
+ 2 mL fehling (A)
+ 2 mL fehling (A)
and fehling (8)
and fehling (B)
(i)
(ii)
5 mL orange juice + 2 mL fehling (A) and fehling (8)
(iii)
(iv)
On heating all these test tubes one of them would not give a red precipitate with Fehling's solution though all of them contain sugar. Which of the following tube will not give red precipitation? (a) (i)
(b) (ii)
(e) (iii)
(d) (iv)
Answers 1. (b)
2. (d)
3. (e)
4. (e)
5. (d)
6. (e)
7. (a)
8. (d)
9. (e)
10. (b)
11. (a)
12. (b)
13.(b)
14. (b)
15. (b)
16. (b)
17.(a)
18. (d)
19. (b)
20. (d)
21. (a)
22. (d)
23. (b)
24. (e)
25.(e)
26. (a)
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Improvement in Food Resources
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VK Biology IX
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