Class VII I.I.T.foundation, N.T.S.E.& Science Olympiad Curriculum & Chapter Notes

2012 VII I.I.T. Foundation, N.T.S.E.& Science Olympiad Curriculum & Chapter Notes

Jai Kumar Gupta Brilliant Public School, Sitamarhi 17/04/2012

VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Curriculum Chapters as per NCERT Text Book

Topics

Topic

Physics-VII Temperature and Its Measurement 1. Heat

Transfer of Heat Seasons and Clothes Air Pressure Winds

2. Winds, Storms and Cyclones

Thunderstorms and Cyclones Protection from Cyclones Time-and-Speed

3. Motion and Time

Graphs Electric Components 4. Electric Current and its Effects

The Heating Effect of Electric Current The Magnetic Effect of Electric Current Reflection Of Light Spherical Mirror

5. Light

Images Formed By Lens Sunlight

Chemistry-VII 1. Fibre to Fabric

Animal Fibre - Wool Animal Fibre - Silk Indicators

2. Acids, Bases and Salts Neutralization

VII I.I.T. Foundation, N.T.S.E.& Science Olympiad Curriculum

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Chemistry-VII Contd. Chapters as per NCERT Text Book

Topics

3. Physical and Chemical Changes

Physical and Chemical Changes

4. Weather, Climate and Adaptations of Animal and Climate

Weather and Climate Climate and Adaptations Soil Profile

5. Soil Soil Types and its Properties 6. Water

Water : A Precious Resource

Biology-VII 1. Nutrition in Plants

Nutrients in Plants Digestion in Humans

2. Nutrition in Animals

Digestion in Ruminants Digestion in Amoeba Respiration

3. Respiration in Organisms

4. Transportation in Animals and Plants

Breathing Transportation in Humans Transportation in Plants Sexual Reproduction in Plants

5. Reproduction in Plants

6. Forests: Lifeline

Asexual Reproduction in Plants Importance of Forest Introduction to Forest Water, Our Lifeline

7. Wastewater story

Water Treatment Importance of Sanitation

VII I.I.T. Foundation, N.T.S.E.& Science Olympiad Curriculum

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VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes Physics Chapters as per NCERT Text Book 1. Heat

Topic Temperature and Its Measurement

Transfer of Heat

Seasons and Clothes

2. Winds, Storms and Cyclones

Air Pressure

Winds

Thunderstorms and Cyclones

Protection from Cyclones

3. Motion and Time

Time-and-Speed

Graphs

4. Electric Current and its Effects

Electric Components

The Heating Effect of Electric Current

The Magnetic Effect of Electric Current

5. Light

Reflection of Light

Spherical Mirror

Images Formed By Lens

Sunlight

VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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1. Heat Temperature and Its Measurement

Temperature

is

a

measure

the

sensation of warmth or coldness of an object, felt from contact with it.

Temperature Temperature is a measure the sensation of warmth or coldness of an object, felt from contact with it. This sensation of touch gives an approximate or relative measure of the temperature. Temperature is measured in different scales, including Fahrenheit (F) and Celsius (or centigrade, C). The units of the Fahrenheit and Celsius scales are called degrees and are denoted by . Swedish astronomer Anders Celsius devised the Celsius scale in 1742. He fixed the

of the scale at the freezing of water, and the

at the

boiling of water. Themometer A thermometer is used to measure the temperature of an object - it is used to find how cold or hot the object is. Galileo invented a rudimentary water thermometer in 1593. He called this device a "thermoscope". However, this form was ineffective as water freezes at low temperatures. In 1714, Gabriel Fahrenheit invented the mercury thermometer, the modern thermometer. The long narrow uniform glass tube is called the stem of a thermometer. The small tube called the bulb, which contains mercury. Mercury is toxic,


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and it is very difficult to dispose it when the thermometer breaks. So, nowadays digital thermometers are used to measure the temperature, as they do not contain mercury. Types of Thermometers There are different types of thermometers that measure the temperatures of different things like air, our bodies, food and many other things. There are clinical thermometers, laboratory thermometers, Galileo thermometers and digital remote thermometers. Among these, the commonly used thermometers are clinical thermometers and laboratory thermometers. Clinical Thermometer: These thermometers are used to measure the temperature of the human body, at home, clinics and hospitals. All clinical thermometers have a kink that prevents the mercury from falling down rapidly so that the temperature can be noted conveniently. There are temperature scales on either side of the mercury thread, one in Celsius scale and the other in Fahrenheit scale. A clinical thermometer indicates temperatures from o note a reading, place the thermometer in the person's mouth. Since the Fahrenheit scale is more sensitive than the Celsius scale, body temperature is measured in degrees Fahrenheit only. A healthy person's average body temperature is between

.

Precautions: 

Wash the thermometer before and after use with an antiseptic solution, and handle it with care.



See that the mercury levels are below the kink and don't hold the thermometer near its bulb. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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

While noting down the reading in the thermometer, place the mercury level along the eye sight.



Do not place the thermometer in a hot flame or in the hot sun. Laboratory Thermometers These thermometers are used to measure the temperature in school and other laboratories for scientific research. They are also used in the industry as they can measure temperatures higher than what clinical thermometers can record. The stem and the bulb are longer when compared to that of a clinical thermometer. A laboratory thermometer has only the Celsius scale ranging from -10o C to 110 o C. Precautions:



A laboratory thermometer doesn't have a kink.



Do not tilt the thermometer. Place it upright.



Note the reading only when the bulb has been surrounded by the substance from all sides. Conversion The Celsius and Fahrenheit scales are related as

.


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Transfer of Heat

When an object is at different a temperature from its surroundings, then heat transfer takes place so the body and surrounding reaches the same temperature.

Heat Heat transfers from hotter objects to colder objects. When an object is at different a temperature from its surroundings, then heat transfer takes place so the body and surrounding reaches the same temperature. Also, heat from a hotter object is transferred to the particles of the surrounding air that are comparatively cooler. For example, when milk is boiled and the flame is off, the milk slowly transfers heat and becomes

cooler.

There are three modes of heat exchange: Conduction, convection and radiation. Conduction Conduction is the transfer of heat from the hotter part to the colder part of an object without the movement of its particles. Also, in conduction, heat gets transferred between substances that are in direct contact with each other. The better the conductor, the more rapidly does the heat transfer take place. For example, when you pop corn in a cooker on a flame, heat is transferred from the flame to the corn by conduction.


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Conductors Materials that allow the flow of heat are called conductors. Examples of good conductors are copper, steel, silver and iron. Insulators Materials that do not allow the flow of heat are called insulators. Examples of insulators are wood, paper, rubber, cork, glass, Bakelite and ceramic. Convection Convection is the transfer of heat by the movement of particles of a medium from one place to another. It takes place only in liquids and gases. Examples of convection are wind currents, the lower floor of a building is cooler than the upper floor, and water is warmer at the surface of a swimming pool or lake. Due to convection, the atmosphere at the sea shore is always pleasant. Radiation The process in which heat flows from one object to another either through a medium or vacuum is called radiation. The heat absorbed from the surroundings by a body increases its temperature. The sun warms the earth through radiation. A camp fire, microwave oven and a light bulb are all examples of radiation.


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Seasons and Clothes

Depending upon the season, we need to choose the clothes we wear.

Summer Cloths In hot weather, white or light coloured clothes suit better, because they reflect the heat and keep the body cool, whereas black clothes retain heat. During summer, clothes made of cotton are more comfortable. Cotton clothes allow the body heat to escape. People wear loose clothes to keep cool. Loose clothes allow air to circulate below the fabric. Thus, loose clothes are more suited during summer than tight fitting clothes. Hence, summer wear should be breathable, light-coloured and loose fitting rather than dark and tight fitting. Winter Cloths In cold weather, warm and thick clothes should be worn. A wool base layer helps maintain body temperature at a comfortable level in either cool or warm conditions. So, woollen garments are suitable for cold weather. As wool is a very good insulator and a poor conductor of heat, it can absorb moisture without becoming wet. Woollen clothes keep the body warm and protect from the cold winds.


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Also, the air trapped between the woollen fibres prevents the flow of heat from the body to the cold surrounding. It also prevents the cold air from coming in contact with the body. Woollen garments have excellent shape retention because of the crimp in the fibres. The crimp creates many tiny air pockets that trap the warm air of the body or form a sort of insulation from the external air. This insulating barrier of air pockets protects from the cold winds. Sweaters, mufflers, cardigans and woollen garments give protection from winter. Thus, dark, thick, woollen garments are suitable during winter.


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2. Winds, Storms and Cyclones Air Pressure

The pressure exerted by air on all bodies at all times in all directions is called air pressure.

Air Pressure The pressure exerted by air on all bodies at all times in all directions is called air pressure. When air moves at high speeds, it creates a low pressure area. The air inside a balloon exerts pressure in all directions, and makes it blow up. Air opposes the motion of a moving object. This is called air resistance. That is why you have to exert yourself and pedal hard when you ride a bicycle. Another example in which air pressure can be observed: Take a glass and fill only 1/3 of it with water. Cover the mouth of the glass with an index card. Now hold the card in place and invert the glass over a sink and remove your hand from the card. The card sticks to the glass. This is due to air pressure. The air outside exerts an upward pressure on the index card. This air pressure is more than the weight of the water in the glass. Winds Winds are caused by variations in air pressure. A wind blows from a region of high pressure to a region of low pressure. The speed of the wind mainly depends on the difference between the pressures of the air in the two regions.


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High speed winds are known to blow away thatched and tiled roofs in rural and semiurban areas. Strong winds can uproot trees and electric poles, and even snap cables. Anemometer The instrument used to measure the speed of wind is called the anemometer. It is usually fixed on the top of a building. Winds

Air

expands

on

heating,and

the

expanded air pushes for more space.

Air expands on heating, and the expanded air pushes for more space. For example: 1) Take two deep pans - one filled with hot water and the other with cold water. To prove that air expands when heated, 

Stretch a balloon across the mouth of a milk bottle and seal it with tape.



Keep this bottle in the hot water pan



The balloon is slowly inflated. This is because the heat from the hot water in the pan heats up the air inside the bottle, which makes the air inside the bottle expand.

Now place the bottle in the pan with cold water. The balloon deflates and shrinks. This is because the air inside the bottle gets cooled and so contracts. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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2) Observe a pressure cooker where the steam comes out of the nozzle and escapes upwards. This is because steam escaping from a pressure cooker is lighter than the relative cool air surrounding it. Thus, hot air rises. Circulation of Wind The equatorial and tropical regions get hotter than the polar regions. The warm air at the equator rises, and the cold air moves in from the polar regions. The air moves due to uneven heating of the earth's surface between the equator and poles, which results in circulation of wind across the globe. Direction of Wind Winds are also formed due to uneven heating of land and water in coastal areas. As the earth rotates on its axis from west to east, these wind currents are not exact. There is a difference in the temperatures of the air over sea and over land. Cold winds from the South Pole move north towards the equator, and whereas winds from the North Pole move south towards the equator. Monsoon Winds The word monsoon is derived from the Arabic word "mausam," which means season. The winds from the ocean carry water in the form of vapours, resulting rains over land. These are called monsoon winds.


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Thunderstorms and Cyclones

A storm with lightning and thunder is called a thunderstorm. It occurs due to the convection of air in hot and humid areas.

Thunderstorms A storm with lightning and thunder is called a thunderstorm. It occurs due to the convection of air in hot and humid areas. Cyclone A natural calamity caused by difference in air pressure in the atmosphere is called a cyclone. A cyclone is a violently rotating windstorm. Cyclones are dangerous. Cyclones begin as thunderstorms. In tropical regions like India, thunderstorms are common, but very few thunderstorms convert into cyclones. In India, the eastern coast is more vulnerable to cyclones than the western coast. In different parts of the world, cyclones are known differently. For example, in America, a cyclone is referred to as a hurricane, while the Filipinos and Japanese called it a typhoon. The largest tropical cyclone recorded was Typhoon Tip that struck Japan in 1979. At its peak strength, the diameter of its eye wall was 2220 kilometres. The wind speeds were recorded at 305 kilometres per hour. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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Formation of Cyclones The formation of a cyclone depends on the speed and direction of the wind, temperature and humidity. A cyclone also arises: 

Due to the difference in the temperatures of the two regions.



A low pressure is created as the air in the high temperature region becomes warm and rises.



The gap in the low pressure area is filled by cold air rushing in from the surrounding areas.



When the warm air arises, it cools, condenses and forms clouds.



When the water vapour in the clouds turns into raindrops, the heat possessed by the water vapour is released into the atmosphere.



The process repeats and the release of heat from the water vapour continues. Precautions During a thunderstorm, move away from open garages, metal sheds and water bodies. During a thunderstorm, sit inside a car, a bus or a closed vehicle, or inside a building. During a thunderstorm, do not:



Rest under a tree



Take shelter under an umbrella with a metallic end



Lie down flat, if in an open place



Sit near a window Humidity Humidity is the amount of water vapour in the atmosphere. As the humidity in a region increases, the difference in temperature also increases. This results in the formation of a cyclone. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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Gales Winds moving at high speeds are known as gales. Eye of a Cyclone The calm and clear area at the centre of a cyclone is called the eye of the cyclone. Tornado A rotating column of high speed winds that appears as a dark funnel-shaped cloud reaching from the ground to the sky is called a tornado. A tornado may form within a cyclone. A tornado forms due to the effect of low pressure in the eye of a cyclone. Objects near the base of a tornado, such as cars, dust, debris and even houses, are sucked into its funnel and thrown out at the top. More than a thousand tornadoes occur every year across the world. Most occur in the United States. Tornadoes occur regularly in the regions around the Atlantic Ocean. Weak tornadoes travel with wind speeds of 50 to 60 km/hr, while a violent tornado can travel at a speed of about 400 km/hr. A tornado is a natural disaster, but not as dangerous as a cyclone.

Protection from Cyclones

Cyclones cause a lot of damage to land, people and property, and create a lot of havoc in the lives of the people.


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Cyclones cause a lot of damage to land, people and property, and create a lot of havoc in the lives of the people. When a cyclone hits an agricultural field, it makes the land infertile and useless for agriculture. A cyclone spares nothing. It worsens the flood situation. There are indirect impacts of a cyclone as well, such as flooding in coastal areas. Flooding not only damages land, but also pollutes drinking water sources. This can cause epidemics. High waves several kilometres away from the shore indicate an upcoming storm. As a cyclone strikes the coast, the intense winds raise the water into a gigantic wave that is pushed towards the shore. High-speed winds during a cyclone can cause major damage to houses, human beings, animals, trees, power supply, and even communication systems such as telephones. Storm Surge A high wall of water moving towards the shore from the ocean is called a storm surge. Storm Tide The combination of a storm surge and a tide is known as a "storm tide". The most dangerous storms are the ones where the storm surge arrives on the top of a high tide, and then the storm reaches an area that might otherwise have been safe. Meteorological Department The department that carries out a scientific study of the atmosphere and focuses on weather forecasting and processes. Tropical cyclones are given names. The names are selected from a list decided by the national meteorological organisation of a country, or by a committee of the World Meteorological Organisation. The names of tropical cyclones that cause major death or destruction are not used again, as a tribute to the people who lose their lives in the disaster.


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Cyclone Alert A warning issued 48 hours before the expected time of a cyclone. Cyclone Warning A warning issued 24 hours before the expected time of a cyclone. A cyclone causes destruction through: 

High-rise waves



High-speed winds that uproot trees, houses and other property



Contamination of drinking water



Heavy rainfall that worsens the flood situation



Flooding of agricultural land by sea water making it infertile Safety measures taken by the government: To keep people safe and secure during a cyclone, the government takes certain measures, such as:



Constructing cyclone warning centres



Making arrangements to relocate people during cyclones



Providing information about a cyclone, and warning people, fishermen, ships, ports, airlines and various government agencies



Delivering accurate and effective cyclone forecasts and warnings Safety measures to follow before and during a cyclone:



Do not move out unless and until required.



Keep a note of all the warnings given by the Meteorological Department.



Keep emergency phone numbers of police, ambulance and fire brigade handy.



Move people and valuable items to a safe place. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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

Store hygienic drinking water.



Help neighbours.



Avoid contact with wet electric lines and switches.


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3. Motion and Time Time and Speed

An object is said to be moving slowly if it covers less distance in a given time.

Moving Slowly An object is said to be moving slowly if it covers less distance in a given time. Moving Fast An object is said to be moving fast if it covers more distance in a given time. Speed The distance covered by an object in a unit time is defined as speed. Objects are said to be in fast or slow motion depending upon the speed of their motion. Speed varies from object to object, and it can be animate or inanimate. Speed is calculated using the expression

The basic unit for time is second, and it can be calculated in minutes and hours, too, depending on the need. The basic unit for distance is metre. So, the unit for speed is metres per second (m/s). Large speeds are measured in kilometre per hour (km/h). The symbols for units are VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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written in singular form only. For example, the speed of the cheetah is 112 km/h, and Speed of giant tortoise = 0.27 km/h. Average Speed The average speed of a moving object is defined as the total distance covered by it divided by the total time taken.

Speedometer An instrument used in vehicles to show speed. Not all moving vehicles have a speedometer. The speedometer has a needle that indicates the speed. For example, a bicycle does not have a speedometer, whereas a car has one. Odometer An odometer is a device on vehicles to track the distance covered. Uniform Motion Objects that move in a straight line and maintain the same speed throughout the distance covered are said to be in uniform motion. Non-Uniform Motion Objects that move in straight line and whose speed varies are said to be in non-uniform motion.


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Osillation A metal ball is considered to have completed one oscillation, if the pendulum moves from its mean position 'Y' and goes to 'X' to 'Z' and back to its mean position 'Y'. Time There are certain events in nature that can help us track time. For example, the phases of the moon indicate the time of the month. There are man-made structures that were constructed to measure time. For example, the Jantar Mantar in Jaipur, which is basically a sun clock, is used to measure time. Water clocks and sand clocks were also used hundreds of years ago to measure time. All mechanical clocks used oscillatory motion to measure time. The time period of a pendulum is the time taken for one full oscillation. The working of a pendulum clock is based on the time period of its pendulum. Winding clocks and wrist watches developed from modifications to the pendulum clock. A quartz clock is more accurate than other clocks because its oscillations are regulated by a quartz crystal.

Graphs

A pictorial representation of two sets of numerical data.


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GRAPH A pictorial representation of two sets of numerical data. The saying, "A picture is worth a thousand words," is exactly true in case of graphs. The data represented in a graph is self explanatory. USES OF GRAPHS Graphs are used for better understanding. For example, using these graphs, the performance of two batsmen can be compared, performance of two bowlers can also be observed in a cricket match. Also, in population studies, these graphs are used to compare the birth and the death rate, and other kinds of data. TYPES OF GRAPHS There are three types of graphs: 

Bar graphs



Pie charts



Line graphs BAR GRAPH A bar graph is also known as a histogram. A bar graph consists of horizontal or vertical bars that show the values of one quantity against another. These are useful when there is a numerical comparison. For example, it compares the performance of a team across matches in a series. PIE CHARTS A circular graph used to represent relative percentages or shares of a total. It looks like a pie cut into several slices, and hence the name pie chart. Each slice is called a sector of


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the chart. A pie chart is used to showcase a whole quantity and the whole quantity is broken into parts. LINE GRAPH A line that joins dots plotted on a graph paper is called a line graph. It is used to show the variation of a quantity with respect to another. A line graph represents two pieces of information that are usually related. It is useful when comparisons are needed. For example, these graphs are used to represent the changes in speed over a journey. PLOTTING A GRAPH To plot a graph on a graph sheet: 

Take a graph paper.



At the centre of the paper, draw two lines perpendicular to each other.



Mark the point of intersection of the lines as 'O.' The horizontal line is called the X-axis, while the vertical line is called the Y-axis. The point of intersection of the two axes is called the origin, "O". Take one quantity along the X-axis and the other along the Y-axis, after choosing suitable scales for both. For every value along one axis, mark a point matching the related value on the other axis. Join the points, and your graph is ready. SHAPE OF THE GRAPH Body in uniform motion: The graph for a body in uniform motion will be straight line making angle horizontally.


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Body at rest: The speed of a body at rest speed is zero at any point of time. Hence, its graph is a straight line along the X-axis. Body in non-uniform motion: For a body in non-uniform motion, the graph is not a straight line.


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4. Electric Current and its Effects Electric Components

A

simplified

conventional

pictorial

representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram.

Circuit Diagram A simplified conventional pictorial representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram. A 'circuit diagram' is also known as an electrical diagram, wiring diagram, elementary diagram or electronic schematic. Electrical Circuit A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit. For a bulb to glow, it must be connected to battery rather than a cell, because a bulb will require more power. So if a circuit requires more power, then a battery should be connected. Cell Holder A compartment that holds two or more cells together to form a battery is called a cell holder. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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Open Circuit If current does not flow through a circuit, then it is said to be an 'open' circuit or incomplete. Its switch is in 'off' position. Closed Circuit A circuit is said to be a closed circuit or complete when current flows through it. Its switch is in 'on' position. Battery A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another. To identify the positive and negative terminals, they are denoted as + and -, respectively. These batteries are used in many devices, such as torch lights, mobile phones, calculators and even automobiles. Symbols Different symbols are used to represent different components of electrical circuits, but the symbols used must be standardised. These symbols are easy to understand, remember and draw.

Component Symbol

Function of the component

Wire

It allows current to flow

z

from one part of the circuit to another. Switch

When the switch is ON position, current will flow.


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When the switch is in OFF position, current will not flow. Cell

It supplies electric current. The positive terminal (+)of a cell is represented by a vertical long line, while the negative

terminal

(-)

is

shown as a parallel, shorter line. Bulb

The bulb glows if the switch is ON, and doesn't glow if it is in OFF position.

Battery

It supplies electric current. A battery is two or more cells connected together.

The Heating Effect of Electric Current

when an electric current flows through the filament of a bulb, it generates heat, and so the bulb becomes hot


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Heating Effect of Electric Current In the 19th century, James Joule studied a property, which says that "when an electric current flows through the filament of a bulb, it generates heat, and so the bulb becomes hot". This property is named the heating effect of electric current. Compact Fluorescent Lamps (CFL's) We use electric bulbs to obtain light. Due to the heating effect, some part of the energy received by the bulb is used up, and hence, some electricity is wasted. CFL's do not depend on the heating effect of electricity to produce light, since they do not use filaments. Using CFL's instead of ordinary bulbs minimises wastage of electricity. In CFL's, light is generated using two electrodes. The fluorescent coating inside each tube makes the light brighter. We use every day many appliances that work on the property of the heating effect of electric current. For example, the electric room heater, electric roti maker, electric iron, toaster, hair dryer, electric stove, immersion water heater, food warmer, electric coffee maker, electric rice cooker and geyser work on the property of the heating effect of electric current. Heating Elements These appliances have coils of wire that produce heat, which are known as heating elements. As current flows through these electrical appliances, the coils of wire inside turn bright orange red in colour. This is because a huge amount of heat is produced. Different appliances have different types of heating elements. The type of heating element depends on the function of the appliance. Some appliances are required to produce more heat than others.


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ISI Mark You should purchase only appliances that bear an ISI mark. ISI stands for Indian Standards Institute. If an appliance bears the ISI mark, it means that it is safe and will not waste electrical energy. Moreover, it is a mark of quality. Factors affecting production of heat The factors that affect the production of heat in a wire through which an electric current is passing are the length and thickness of the wire, the duration of flow of current, and the material of the wire. Electric Fuse The electric fuse works on the principle of the heating effect of electric current. An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it. It is made of a special material. As the current increases beyond a limit, the wire in the electric fuse melts and breaks off. The fuse is then said to have blown off. The circuit is broken and current stops flowing through it. Thus, a fuse prevents fires. There are various types of fuses. Some fuses are used only in buildings, while others are used in appliances. Reasons for Excessive Currenct When all the appliances are connected to the same socket, these appliances draw more current, and so the load increases. When the insulation on the wires is torn, two wires carrying current touch each other directly. This causes a spark, which leads to fire. This is termed as a SHORT CIRCUIT. If a fuse is not used, then overloading and short circuits result in fire.


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Miniature Circuit Breakers (MCB) Instead of fuses, MCBs are used nowadays because these are switches that turn off automatically when there is an overload or a short circuit. After solving the problem in the circuit, the switch can be turned back on, and then the current flows as usual.

The Magnetic Effect of Electric Current

When electric current flows through a wire wound around an iron bar, the bar behaves like a magnet.

Electromagnet When electric current flows through a wire wound around an iron bar, the bar behaves like a magnet. This magnet is called an electromagnet. An electromagnet is formed due to the magnetic effect of electric current. This magnetic effect of electric current was discovered by Hans Christian Oersted. Once, while preparing for a lecture, he noticed that there was a deflection in the needle of a magnetic compass kept near a wire that was connected to a battery. This deflection occurred every time the battery was switched on and off. He realised that a magnetic field is created around a current-carrying wire in a circuit. The components required to create an electromagnet are two pieces of insulated copper wire, a nail, a battery containing two cells, a bulb with a holder, and some paper clips made of iron. The bulb is also used for making an electromagnet since it serves as a resistance to the current in the circuit and it prevents the battery from quick discharge.


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Construction of an Electromagnet 

Take a nail and wind a copper wire around it without any overlap, as shown in the figure.



Remove the insulation on the wire at the two ends



Connect one end of the wire to the battery and the other to one terminal of the bulb holder.



Connect one end of the second wire to the remaining terminal of the bulb holder, and the other end to the battery.



Place the paper clips near the nail.



When you switch on the current, the paper clips will cling to the nail. This is because the nail becomes an electromagnet.



When the battery is disconnected, the nail is no more an electromagnet. The paper clips will not cling to the nail. Application of Electromagnet Electromagnets are used in medicines, toys, iron industries, and most commonly in the electric bell. Cranes are used for lifting material, separating iron from scrap in industries, and to lift cars. These work on the principle of the electromagnet. Electromagnets are also used in electromagnetic trains called Maglev's. Construction and Working of an Electric Bell Circuit



An electric bell consists of an iron core, on which is wound a wire as a coil.



One end of the coil is connected to one terminal of a battery, and the other end to a steel rod that acts like a spring for the hammer touching the screw contact.



The other terminal of the battery is connected to the screw contact with a switch in the middle.


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Working 

Electric current flows through the coil when the switch is ON, and the iron core acts as an electromagnet.



The iron core attracts the hammer towards it.



The hammer hits the bell and produces a sound.



The circuit breaks at the screw contact when the hammer moves towards the iron core. At this point, the iron core ceases to be an electromagnet.



The hammer is pulled back to its original position due to the spring action of the steel rod, and then touches the contact again to complete the circuit.



The circuit is completed and current flows through the coil again, and the hammer strikes the bell again.



The process repeats itself and you hear a ringing sound since the hammer keeps hitting the bell, until the switch is released.


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5. Light Reflection of Light

The path of light is always straight and never curved. Light doesn't bend.

Light The path of light is always straight and never curved. Light doesn't bend. Examples to show that light travels in a straight line are light emitted by a torch light and light emitted from the headlights of a vehicle. The direction of light can be changed only by reflection. Reflection of Light The bouncing of light by any smooth surface, like a mirror, is called reflection of light. Image Due to the reflection of light, the impression of an object formed in a mirror is called the image of the object. As the distance of the object from the mirror increases, the distance of the image also increases. The concept that images in a mirror are located at the same distance behind the mirror as the object in front of it is mainly used in interior decoration and in architecture to make rooms appear brighter and bigger. Moreover, placing a mirror near lights, chandeliers and table lamps reflects the light over a larger


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area, and makes the room appear brighter. Images that cannot be captured on a screen are called virtual images. Left-Right Inversed As the name suggests, images are inversed, i.e. the right part of an object appears on the left in its images, and the left part of the object appears to the right. For example, the word 'AMBULANCE' is painted left-right inversed on the vehicle so that when the driver of a vehicle in front looks into his rear - view mirror, he can make out the word AMBULANCE quickly and give way. Characteristics of an Image The image formed by a plane mirror is: 

The same size as that of the object



Left-right inversed



Erect and virtual



Formed behind the mirror at the same distance as the distance of the object in front from the mirror A mirror maze is created based on the principle of reflection in plane mirrors. The maze has several plane mirrors placed at fixed angles to each other. When a person enters a mirror maze, he finds several images of himself and several passages. There is only one passage that is real, while all the others are all just images.


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Spherical Mirror

These have curved reflecting surfaces and are also called curved mirrors. These mirrors are made from a hollow sphere.

Spherical Mirrors These have curved reflecting surfaces and are also called curved mirrors. These mirrors are made from a hollow sphere. There are two types of curved surfaces at each hemisphere. The inner curved surface is termed as concave, while the outer is called convex. Spherical mirrors are different from plane mirrors due to their reflecting surface. Types of Spherical MIrrors There are two types of spherical mirrors. 

Concave mirror



Convex mirror Concave Mirror If the reflecting surface of a mirror is concave, then it is called a concave mirror. A concave mirror is also known as a converging mirror. It is used to magnify objects. Concave mirrors are used by dentists to obtain a magnified image of the teeth. They are also used in solar heaters or solar concentrators, and as reflectors in flashlights, and headlights of cars and scooters. VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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The image formed by a concave mirror when the object is placed close to it is virtual, erect and magnified. The image formed by a concave mirror when the object is moved away from it is real, inverted, and magnified. The image formed by a concave mirror when the object is placed far away from it is real, inverted and diminished. Convex MIrror If the reflecting surface of a mirror is convex, then it is called a convex mirror. A convex mirror is also known as a diverging mirror or fish eye mirror. The image formed by a convex mirror is virtual, erect and diminished. It means that a larger area is visible in a convex mirror than in a plane mirror of the same size. That is why convex mirrors have a variety of applications - as reflectors at sharp turns and tricky or 'blind' corners and in parking lots, and as rear-view mirrors in cars and on motorcycles. Rear-view mirrors enable the driver/rider to watch the road behind them. They are also used in super markets, stores and ATM centres as a security measure. Objects like thumb tacks, Christmas baubles and sunglasses act as convex mirrors. Virtual Images The image formed by a plane mirror cannot be captured on a screen, and is called a virtual image. Real Images Images that can be captured on a screen are known as real images. For example, in a camera, images are real and can be captured on the negative, which acts as a screen.


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Opaque Spherical Surface In an opaque spherical surface, the silvered surface acts as a mirror. So, a concave mirror will have its concave side silvered, while a convex mirror will have its convex side silvered. Transparent Spherical Surface For a transparent spherical surface, if the concave surface is silvered and later coated with red oxide, then the mirror acts as a convex mirror. Also, if the convex surface is silvered and later coated with red oxide, then it acts as a concave mirror.

Images Formed by Lens

It is a lens that possesses at least one surface that curves inwards.

CONCAVE LENS: It is a lens that possesses at least one surface that curves inwards. When light rays are incident on a concave lens, they bend outwards or diverge. The rays diverge away from each other. Thus, a concave lens is also called a diverging lens. A concave lens is thinner at its centre than at its edges, and is used to correct short sightedness. It does not focus at a single point. The image formed by a concave lens is upright, virtual and smaller than the object. For example, the images seen through a peephole are different from normal holes, because these peep holes contain concave lenses.


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CONVEX LENS: A convex lens makes the object magnified, when viewed through it. A convex lens is thick in the middle and thin at its edge. When light rays pass through a convex lens, they bend inwards and converge at a common point to form an image of the source of light. Rays from the sun converge to form its image as a bright spot. A convex lens converges light rays. Therefore, it is also called a converging lens. The image formed when the object is placed close to a convex lens is virtual, erect and magnified. Virtual images cannot be caught on a screen. Images that are caught on a screen are called real images. When the object is placed at a distance from a convex lens, the image formed is real, inverted and diminished. Applications of Lenses Lenses are used in magnifying glasses, peep holes, cameras, bioscopes, binoculars, telescopes, microscopes and projectors. A refracting telescope uses a concave mirror and a convex lens.

Sunlight

A band of colours extending from violet to red is a rainbow. A rainbow is formed by the refraction and reflection of the sun's rays through raindrops.

Rainbow A band of colours extending from violet to red is a rainbow. A rainbow is formed by the refraction and reflection of the sun's rays through raindrops. When it is raining in one VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Physics Chapter Notes

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part of the sky and sunny in another, a rainbow appears. The centre of the rainbows arc is always directed away from the sun. It is believed that in the past, Norsemen saw rainbows as bridges for gods to come to the earth from their home in the sky. Norsemen were the inhabitants of Norway. A rainbow lasted for about 9 hours on 14th March, 1994, at a place called Wetherby in Yorkshire, England. Although sunlight appears white, it is composed of seven colours. The colours in a rainbow are the colours of sunlight. A rotating disc has a pencil that serves as a rotator. The disc is covered with violet, indigo, blue, green, yellow, orange and red coloured papers When the disc is rotated, it appears white instead of the individual colours. This is because a mixture of colours of the rainbow in proper proportions produces white colour. The colours of a rainbow can be represented by the acronym: VIBGYOR: V Violet, I - Indigo, B - Blue, G - Green, Y - Yellow, O - Orange and R - Red. Dispersion of Light through a Prism Take a glass prism. Allow a narrow beam of sunlight to pass through a small hole in the window of a dark room to fall on one face of the prism. The light bends when it passes through the prism. Now allow the light coming out of the other face of the prism to fall on a white sheet of paper or a white wall. Different component colours of white light bend differently, and so the constituent colours can be seen separately. Thus, the colours are said to have dispersed after passing through the prism.


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VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Chemistry Chapter Notes Chemistry Chapters as per NCERT Text Book 1. Fibre to Fabric

Topics Animal Fibre - Wool Animal Fibre - Silk

2. Acids, Bases and Salts

Indicators Neutralisation


Physical and Chemical Changes

4. Weather, Climate and Adaptations of Animal and Climate

Weather and Climate

5. Soil

Soil Profile

Climate and Adaptations

Soil Types and its Properties 6. Water

Water : A Precious Resource

VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes

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1. Fibre to Fabric Animal Fibre - Wool

Wool comes mostly from sheep. It was the first fibre to be spun into yarn, and it provides more warmth than other animal fibres.

Wool comes mostly from sheep. It was the first fibre to be spun into yarn, and itprovides more warmth than other animal fibres. Apart from sheep, wool also comes from the angora goat, yak, llama, alpaca, and even camels. All these animals have a thick coat of hair or fleece, which keeps them warm. Wool is obtained from this fleece. Sheep wool is more commonly available in India. In Tibet and Ladakh, yak wool is more common, whereas in Jammu and Kashmir, it is the angora wool. The famous Pashmina shawls come from the soft under-fur of the Kashmiri goat. In South America, the llama and the alpaca are two animals that yield wool. Actually, there are many different breeds of sheep that are reared in different parts of our country to obtain wool. Some breeds of sheep are selectively reared. This means that their parents are chosen for their special characteristics to give birth to them. For example, some sheep are selected because they have soft under-hair. This process is called 'selective breeding'. The Nali and Lohi breeds are found in Rajasthan and Punjab, the Rampur bushair in Uttar Pradesh and Himachal Pradesh, and the Bakharwal in Jammu and Kashmir. Gujarat breeds the Marwari and Patanwadi sheep. Each breed yields wool used for different purposes. 

Nali breed wool is used to make carpet wool.



Patanwadi wool is used for hosiery.



Lohi wool is of very good quality, and is used for making clothes.



Bakharwal wool is used for shawls.


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Sheep are herbivores, and prefer grass and leaves. However, shepherds also feed them mixtures of pulses, corn, jowar, oil cakes and minerals. In winter, they are fed leaves, grain and dry fodder. 

Shearing is the first step in processing fibre into wool. It is the removal of the fleece of the sheep along with a thin layer of the skin.



The next step is to clean the sheared skin and hair. This is done in big tanks to remove the grease, dust and dirt. This is called scouring.



The fleece is sorted according to its texture and type.



Since the fibres are mostly black, brown or white in colour, they can now be dyed in various colours.



Once the dyeing process is complete, the fibres are straightened, combed and rolled into yarn.



The longer fibres are made into wool for sweaters, while the shorter fibres are spun and woven into woollen cloth. In our country, many people earn their livelihood from the wool industry. However, the sorter's job can be dangerous. They can get infected by a bacterium called anthrax, which causes a fatal blood disease called sorter's disease. When workers face such risk due to their occupation, it is called an occupational hazard. Sheep rearing is a lot of hard work.

Animal Fibre - Silk

Silk is the queen of textiles. It is an animal fibre produced by the silkworm to build its cocoon.

Silk is the queen of textiles. It is an animal fibre produced by the silkworm to build its cocoon. Silk was discovered in China, when empress Si-lung-Chi was worried about the damaged mulberry leaves in her garden. Emperor Huang-ti found that white worms were eating up the mulberry leaves and spinning shiny cocoons. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes

Page 3

Silkworms are not worms actually, but the larvae or caterpillars that have hatched from the eggs of the silk moth. Different types of silk moths yield different types of silk yarn, such as: 

Tassar silk



Moonga silk



Kosa silk Silk is the strongest of all natural fibres. A soft silk yarn is as strong as a comparable thread of steel. Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk.



The female silk moth lays hundreds of eggs. These are stored on strips of cloth or paper.



The eggs are then sold to silkworm farmers, who rear them under specific hygienic conditions.



When the mulberry tree bears a fresh crop of leaves, the eggs are warmed suitably so that the larvae hatch from them.



The larvae, caterpillars or silkworms are then stored in clean bamboo trays and are fed freshly chopped mulberry leaves. They eat day and night, and grow to enormous sizes.



The bamboo trays are provided with small racks or twigs to which the cocoons can be attached.



This happens usually 25 to 30 days later, when the caterpillars stop feeding and move to the twigs to spin cocoons. The silk moth develops inside these cocoons.



As caterpillars eat and grow bigger, they also shed their skin. Underneath the old one is a new skin. Caterpillars may shed skin four or five times. Extracting silk from the cocoon:



The first step is to separate the silk fibre from the cocoon. For this, they need to be exposed to warmth.



Piles of cocoons are kept under the sun, boiled or exposed to steam. The warmth causes the silk fibre to separate from the rest of the cocoon.



The next step is called reeling the silk, which is the process of delicately unwinding the fibre from the cocoon. These silk filaments are soft, and 300 to 900 metres long.



Reeling is also done in special machines.



The silk thread is then bleached and dyed into many shades. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes

Page 4



The silk fibre is now spun into silk thread, which is then woven into silk cloth by weavers. In our country, women are involved in a big way in the sericulture industry. They contribute to processes of rearing of silkworms, reeling of silk from cocoons, and processing of raw silk into fabric. This enterprise contributes to the nation's economy and also helps rank India among the leading silk producing countries. Of course, China leads the world in silk production.


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2. Acids, Bases and Salts Indicators

Many substances that you encounter in your daily life have different properties. One major difference between substances is whether they are acidic or basic.

Many substances that you encounter in your daily life have different properties. One major difference between substances is whether they are acidic or basic. Acidic substances taste sour. Some examples are curd, lemon juice, tamarind, spinach and vinegar. These contain natural acids. Basic substances taste bitter and feel slippery to the touch. Some examples are baking soda and milk of magnesia. There are special substances that are used to test whether something is acidic or basic. These substances are called indicators. Indicators change their colour when added to an acidic or basic solution. Some natural indicators are litmus, turmeric and china rose petals. Litmus is a natural dye extracted from lichens. It is the most commonly used natural indicator. A solution of litmus turns red if it is acidic, and blue if it is basic. Turmeric changes colour to indicate acidic and basic substances. It is yellow in acids and reddish brown in basic solutions. China rose is also a natural indicator. A solution of china rose turns green in a basic solution, and bright pink or magenta in an acidic solution. Acid rain is rain that contains a lot of acid. This acid is created when pollutants in the air, such as carbon dioxide, sulphur dioxide and nitrogen dioxide, dissolve in rainwater, and form acids like carbonic acid, sulphuric acid and nitric acid


Page 6

This rain causes a lot of damage to buildings, plants and animals. This is one important reason why we must avoid polluting our atmosphere. There are certain substances that indicate the acidic or basic nature of other substances. Such special substances are called indicators. An indicator changes its colour to show the nature of a substance. Some natural indicators are turmeric, litmus and China rose. Litmus is a common natural indicator extracted from lichens. Litmus has a purple colour in a neutral medium, red colour in an acidic medium, and blue in a basic medium. When a drop of freshly prepared lemon juice is put on red litmus, it remains red, indicating the acidic nature of lemon juice. If blue litmus is used instead, then it turns red, again indicating the acidic nature of lemon juice. Turmeric paper changes colour in a basic medium. In an acidic medium, it remains yellow, while in a basic medium, it turns reddish brown. When a drop of soap solution is put on turmeric paper, it turns red. This indicates the basic nature of soap solution. S. No Test solution

Effect on turmeric paper

1

Lemon juice

Yellow

2

Orange juice

Yellow

3

Lime water

Reddish brown

4

Milk of magnesia Reddish brown

S. No Name of acid /base Effect on litmus paper Effect on turmeric paper 1

Hydrochloric acid

Blue litmus turns red Remains yellow

2

Sulphuric acid

Blue litmus turns red Remains yellow

3

Sodium hydroxide

Red litmus turns blue Turns reddish brown

4

Potassium hydroxide Red litmus turns blue Turns reddish brown


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China rose is another indicator extracted from China rose petals. In an acidic medium, it exhibits dark pink (magenta), while in a basic medium, it exhibits green colour. S.No.

Name of the acid

Effect on China rose

1

Hydrochloric acid

Dark red

2

Sulphuric acid

Dark red

3

Sodium hydroxide

Green

4

Potassium hydroxide Green

Neutralisation

Substances have either acidic, basic or neutral properties.

Substances have either acidic, basic or neutral properties. Acids are sour to the taste, and include substances like curd, vinegar, lemon, orange juice, etc. Bases are bitter to the taste and slippery to the touch, and include substances like baking soda milk of magnesia, etc. When an acid is mixed with a base in the right proportion, they neutralise the effect of each other. That means the acidic nature of the acid and the basic nature of the base are destroyed. This reaction is called neutralisation. The neutralisation reaction between an acid and a base can be identified by an indicator. For example, for the reaction between hydrochloric acid and sodium hydroxide, phenolphthalein is added as an indicator. Phenolphthalein is pink in sodium hydroxide. When hydrochloric acid is added to it, the colour slowly fades to pale pink and then colourless. This change in colour indicates neutralisation.


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The neutralisation reaction between hydrochloric acid and sodium hydroxide can be written as Hydrochloric acid +Sodium hydroxide → Sodium chloride + Water Heat is also produced during a neutralisation reaction. Neutralisation is useful in our daily life. Acidity caused by indigestion can be reduced by neutralising the hydrochloric acid in the stomach by a base, like milk of magnesia. An ant's sting gives a lot of pain due to formic acid. It can be neutralised by applying calamine lotion, or rubbing with baking soda. Excessive use of chemical fertilisers makes soil acidic. Neutralising the soil with a base like quick lime, which is calcium oxide, or slaked lime, which is calcium hydroxide, will make this soil suitable for plants. Neutralisation is the reaction between an acid and a base to form salt and water. During neutralisation, salt and water are formed, along with the release of some heat. Eg: HCl + NaOH------------>NaCl + H2O + Heat Eg: H2SO4 + 2NaOH--------------->Na2SO4 + 2H2O + Heat The stomach contains hydrochloric acid, which helps in the digestion of food. However, when this acid is produced in excess, it causes indigestion, which is painful. An antacid such as milk of magnesia neutralises the excessive acid in the stomach, and provides relief from the pain due to indigestion. Ant sting contains formic acid. When an ant bites, it injects this formic acid into the skin. This causes pain. It can be neutralised by rubbing the ant bite with moist baking soda, which contains sodium hydrogen carbonate (NaHCO 3), or with a solution of calamine, which contains zinc carbonate (ZnCO 3). Excessive use of fertilisers makes soil acidic. As a result, plants cannot grow properly, and the yield decreases. Adding a base like quick lime, (calcium oxide) or slaked lime (calcium hydroxide) neutralises the soil and makes it suitable for plants. Similarly, when soil is basic in nature, organic matter is added to release acid and make it neutral, and thus, suitable for plants.


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Factory waste contains acids. This waste must be treated with bases for neutralisation before it is released into a water source. Otherwise, it can cause damage to living organisms in the water source.

VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 10


All changes that you see can be broadly divided into physical and chemical changes

All changes that you see can be broadly divided into physical and chemical changes. Some changes affect only the physical properties of the substance that is undergoing change. Physical properties include shape, size, colour and state of matter. 

Some properties of physical changes are: A physical change is temporary. No new substance is formed when a physical change takes place. Forms of energy, such as heat, light and electricity, are neither emitted nor absorbed in a physical change. A physical change is generally reversible. Some changes are in the form of chemical reactions, which lead to the formation of new substances. These are called chemical changes. These changes may be accompanied by the emission of heat, light or sound, a change in colour, or the formation of a gas.



Some properties of chemical changes are: A chemical change is permanent. A new substance is formed. Forms of energy, such as heat, light or electricity, may be emitted or absorbed during a chemical reaction. A chemical change is generally irreversible. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 11

Crystallisation is a physical change, since the process involves a change in the state of matter. No new substance is created in the process of crystallisation. Water and oxygen in the air react with iron to create a new substance called rust. The properties of rust are different than that of iron. This is a chemical change. The rusting of iron can be prevented by coating iron with something else, such as paint, or with zinc through a process called galvanisation. The process of galvanisation is also used in many other places, such as to prevent the rusting of iron pipes that carry water to our homes. Physical changes: Crushing of a chalk piece Boiling of water Melting of ice-cream Evaporation of water Chemical changes: Digestion of food Formation of calcium carbonate Rusting of iron Burning of magnesium ribbon Chemical change is a permanent change in which new substances are formed with different properties along with the evolution or absorption of some kind of energy. Some examples for chemical change are: 

Rusting of iron, as rust cannot be converted back into iron by physical means.



Burning of fuels like petrol, kerosene, diesel, wood, charcoal and coal.



Digestion of food by living organisms.



Photosynthesis in plants.



Butter turning rancid (sour).



Fermentation of sugarcane juice and fruit juice.



Charring of sugar into charcoal on strong heating. It is important to note that when a chemical change occurs in a substance, then we can say that a chemical reaction has taken place. For example:



The metals that we use in our everyday life are obtained from their ores by carrying out a series of chemical reactions.



All kinds of plastics are prepared by chemical reactions. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 12



New medicines are produced by a series of chemical reactions.



All kinds of building materials are prepared by chemical reactions. o

Take a square paper and cut it into four small square pieces of equal size. Now cut each square piece further into four small square pieces. These small square pieces cannot be joined to get back the original big paper. This is nothing but a change in the size of a substance, which is a change in a physical property.

o

Crush a chalk into powder. Then add some water to the chalk dust to make it into a paste, and then roll it into a chalk. Again, this is nothing but a change in the size of a substance, which is a change in a physical property.

o

Take some ice in a tumbler. Place the tumbler in sunlight. Some ice melts into water. This is change in the state of a substance is a change in a physical property.

o

Take some cold water in a container and then heat it so that at a particular temperature, it starts boiling. You can observe steam rising from the surface, which is nothing but a change in the physical state of a substance. The vapours can be condensed back into liquid by placing an inverted container over the vessel.

o

Hold a hacksaw blade with the help of a pair of tongs over the flame of a gas stove for some time.

o

There is a change in the colour of the blade. On cooling, the blade returns to its original colour. This is nothing but a change in the colour of a substance, which is a change in a physical property.

o

All these changes indicate a change in physical properties, like size, state and colour.

If articles made of iron are left in open air for some time, they get coated with a brown powdery substance, called rust. This process of iron changing into rust is called rusting. Rusting of iron occurs only if iron comes in contact with moist air. The process of rusting can be represented as: Fe+O2 (from air) +H2o (water) ------------->Fe2O3 (rust) No rusting occurs if iron comes in contact with only water or air. Moist air contains both oxygen and water, and hence, iron gets rusted easily. Rust is a chemical change that causes huge damage to iron articles like cars, ships, rails, bridges, machines, etc.


If we prevent iron articles from coming in contact with air or water, or both, then rusting can be stopped. Some methods to prevent of rusting are: 

Oiling and greasing



Painting



Coating with other metals



Converting iron into stainless steel Oiling and greasing: A thin layer of oil or grease on an iron object prevents it from coming in contact with moist air. Thus, rusting can be stopped. Painting: If iron articles like gates, chairs, bodies of cars, trucks, ships, etc. are painted, then it prevents moist air from coming in contact with iron. Hence, rusting stops. Coating with other metals: When iron sheets are dipped in molten zinc, a thin layer of zinc gets coated over the sheets. This is called galvanised iron. This zinc layer prevents iron from coming in contact with moist air, and stops rusting. Converting iron into stainless steel: Molten iron is mixed with a certain amount of carbon, chromium and nickel to form an alloy called stainless steel. This doesn't rust in moist air. So it is used for making household utensils and surgical instruments. The process of obtaining crystals of a soluble substance from its hot saturated solution is called crystallisation. Crystallisation is only a physical change because no new substances are formed during the process - it involves only a change in physical state. Crystallisation is used to obtain pure substances from naturally occurring impure substances. Here's an experiment to see how crystallisation occurs. Take 100 ml of water in a beaker and heat it on a Bunsen burner.


When water begins to boil, add about 2 ml of dilute sulphuric acid, and then a spoonful CuSO4. Stir the contents with a glass rod. If all the CuSO4 dissolves, then add another spoonful. Continue until the CuSO4 stops dissolving in water. Stop heating and filter the saturated copper sulphate solution into another beaker. Place this beaker in a trough containing hot water, and cover the beaker with a cardboard. Leave the apparatus for 24 hours. After 24 hours, you will find big blue crystals of pure CuSO4 at the base of the beaker. Filter the crystals and dry in warm air.


4. Weather, Climate and Adaptations of Animal and Climate Weather and Climate

The day-to-day conditions of the atmosphere at a place with respect to elements like temperature, humidity, rainfall, wind speed, etc.

The day-to-day conditions of the atmosphere at a place with respect to elements like temperature, humidity, rainfall, wind speed, etc. is called the weather of that place. The atmosphere is all around us - we cannot see it, but it keeps us warm. Without it, the earth would be a lifeless ice ball. In addition, the atmosphere absorbs or deflects incoming ultraviolet rays and other charged particles. The temperature is low early in the morning, and increases by noon. It decreases again towards the evening, and the cycle continues Similarly, rain, snow, thunder and lightning are constituents of weather. Sometimes, the weather is violent, and sometimes, peaceful and quiet. The sun is responsible for all the changes in the weather. We know that the sun is a huge sphere of hot gases and has a very high temperature. The distance between the sun and us is very large. The sun is the chief source of light and heat for the earth. It is also the primary source of energy, and causes changes in the weather. The energy absorbed and reflected by the earth's surface, the oceans and the atmosphere play an important role in determining the weather at any place. Also, gases like carbon dioxide, methane and water vapour play a role in determining the weather. The weather in coastal areas is very different than that in a desert or hilly areas. The maximum temperature of the day is recorded during the afternoon, while the minimum temperature is recorded early in the morning.


In winters, it gets dark early and you don't get much time to play with your friends. Meteorologists record the weather every day. The records of the weather are preserved for several decades. These records help us determine the pattern of the weather at a place. The average weather pattern taken over a long time, say, 25 years, is called the climate of the place. The mean temperature for a given month is found in two steps. First, we find the average of the temperatures recorded during the month. Next, we calculate the average of such temperatures over many years. The result is the mean temperature. Mean temperature helps compare the weather at two different places. For example, if we compare the temperatures of Thiruvananthapuram in Kerala and Srinagar in Jammu and Kashmir, we can conclude that Thiruvananthapuram is very hot and wet than Srinagar, which is moderately hot and wet for some parts of the year. Let's consider another place like Rajasthan, which has high temperatures during most parts of the year, but very low temperatures in winter, which lasts for a few months. The region receives scanty rainfall. Therefore, it is known as typical desert climate. North-eastern India receives rain for a major part of the year. Hence, we can say that the climate of the region is wet.

Climate and Adaptations

Different parts of the earth have different types of climate. The sun is responsible for this difference in climatic conditions.

Different parts of the earth have different types of climate. The sun is responsible for this difference in climatic conditions. Five major types of climates are recognised, based on the annual and monthly averages of temperature and precipitation.




Moist Tropical Climates are known for their high temperatures and large amount of rain around the year.



Dry Climates are characterised by little rain and a high daily temperature range.



In Humid Middle Latitude Climates, land or water differences play a key part. These climates have warm, dry summers, and cool, wet winters.



Continental Climate is characterised by winter temperatures low enough to support a fixed period of snow cover every year, a relatively moderate precipitation

occurring

mostly

in

summer,

and

an

even

distribution

of

precipitation. 

Polar areas have cold climates as they are covered by ice almost all the year round. Most areas are covered by glaciers or by a semi-permanent layer of ice. Climate has an intense effect on all living organisms. Animals adapt themselves to survive various conditions in which they live. Animals that live in extreme climates acquire some special features to protect themselves from it. For example, the camel has a hump to store food in the form of fat, and hooves to tread on the desert sand with ease. The temperature in the polar areas may go down to minus 37 degrees centigrade during winters. Animals like polar bears, penguins, many types of fish, musk oxen, reindeer, foxes, seals, whales and birds are found in the polar regions. Polar bears, for example, protect themselves with the thick fur on their bodies.



They have two layers of fur for protection from the extreme climate.



They also have a layer of fat under the skin, and are very well insulated. In fact, they often take rest to avoid getting overheated.



The polar bear often goes for a swim to cool off on warm days. Its wide and large paws are useful for swimming as well as for walking on the snow. The bodies of penguins are white, and merge into the background. They have a thick layer of skin and move around in groups to keep warm. Their streamlined bodies and webbed feet make penguins swift swimmers. Water retains its warmth under the icy layer. Fish go deeper in the water to stay warm. Birds have to stay warm to survive. Hence, at the onset of winter, these birds migrate to warmer areas. They come back again in the summer. Siberian cranes migrate to far-off places like Bharatpur in Rajasthan, Sultanpur in Haryana and also to some wetlands of north-eastern India. They fly here all the way from Siberia. Birds travel thousands of kilometres to migrate. During the VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 18

day, the sun guides them, and the stars do so in the night. Animals adapt themselves to hot climate in the tropical regions, where the average temperature is higher than 15 degrees centigrade. At the peak of summer, the temperature may cross 40 degrees centigrade. Throughout the year, day and night are equal in duration. These regions receive abundant rainfall. A significant feature about this region is the tropical forest. A wide variety of plants and animals are found in these regions due to the continuous warmth and rain. The major types of animals living in this type of rainforests are monkeys, apes, gorillas, lions, tigers, elephants, leopards, lizards, snakes, birds and insects. o

Most tropical animals have sensitive hearing, sharp eyesight and thick skin. They also have skin colour that helps them to disguise and protect themselves from predators.

o

All animals have some special feature, like good eyesight, sharp claws, long beaks, sensitive hearing or long trunks, to protect themselves.

o

The toucan has a long, large beak. This helps it reach the fruits on branches that are otherwise too weak to support its weight.

o

The elephant has such large ears and tusks.

o

The tusks are modified teeth and are used to tear the bark of trees for food.

o

The large ears help it hear even very soft sounds. They also keep it cool in this hot and humid climate.


5. Soil Soil Profile

Soil is formed when rocks are broken down by the action of wind, water and climate. This process is called weathering.

Soil is used in: o

Agriculture

o

Gardens

o

Pottery Soil is formed when rocks are broken down by the action of wind, water and climate. This process is called weathering. The characteristic features of a soil depend upon the rocks from which it has been formed and the kind of plants that grow in it. Soil forms different layers of particles of different sizes. Each layer is different from the other in texture, colour and chemical composition. Even the thickness of each layer is not the same. A vertical section that shows different layers of soil is called a soil profile. Each layer is called a horizon.



Top soil or Horizon-A



Middle layer or Horizon-B



Horizon-C



Bed rock Horizon-A



The topmost layer is dark in colour, and contains the remains of dead plants and animals. This rotting matter is called humus. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 20



This layer of soil is called topsoil or A-horizon.



It is made up of humus and minerals, and makes the soil fertile.



It is soft and porous, and can retain more water than the other layers.



Many tiny organisms, such as beetles, worms and rodents, live in the topsoil.



The roots of small plants do not go down very deep and can be found in the topsoil. When plastic bags are disposed off, they usually get embedded in the topsoil. Since plastic does not get decomposed naturally, the polythene bags pollute the soil and kill the organisms that live in it. Stop using polythene bags. Horizon-B



The layer below the topsoil is called B-horizon or the middle layer.



The middle layer is less porous than the topsoil, and is, therefore, harder.



It contains more minerals as compared to the topsoil, but less quantity of humus. Horizon-C



It is not as compact as the two layers above it. This layer is called C-horizon.



It has cracks running through it.



It is mostly made up of rocks. Bedrock

o

The bottom-most layer in the soil profile is called bedrock.

o

This is far more solid in composition than the other layers and is very hard.

o

It is difficult to dig up this layer even with a spade.


Soil Types and its Properties

Soil has some characteristics that form the basis for its classification into various types, and also the types of crops that are grown in it.

Soil has some characteristics that form the basis for its classification into various types, and also the types of crops that are grown in it. The rate of absorption is different for different types of soils. This phenomenon of absorption of water by soil is termed as percolation.

The rate of absorption of a soil depends on its composition. As we know, soil is formed by the weathering of rocks. The amounts of sand and clay depend on the rock from which the soil particles have been formed. Soil is not similar everywhere. Soil is classified into various types based on the appearance and proportion of particles. 

Sandy soil



Clay soil



Loamy soil

Properties of sandy soil: 

If the soil is made of a greater proportion of big particles, it is called sandy soil.



The sand particles are relatively large. They cannot fit closely together.



There are large spaces between them. These places are filled with air.



Therefore, in this type of soil, water absorption is very high as the water passes quickly through these spaces.



These soils are light, well aerated and dry.

Properties of clay soil:




It is made of a relatively high proportion of fine particles.



These soils have very less space between particles.



Because the particles are smaller in size, water can be trapped in the tiny gaps between them.



Clay soils are heavy and hold more water.

Properties of loamy soil: 

It is a mixture of sand, soil and silt.



Silt particles are present between the particles of sand and soil.



It also contains humus, and is, therefore, considered the best for the growth of plants.



The percolation rate is between that of sandy soil and clay soil.

Climatic factors as well as the components of the soil determine the types of vegetation and crops that grow in a particular area. 

Cereals like wheat and gram are grown in clay and loamy soils, because these soils have better water retention capacity.



Soils rich in clay and organic matter with good water retention capacity are ideal for paddy.



Loamy soils, which drain water easily, are suitable for lentils and other pulses.



For cotton, loamy or sandy soils are more suitable, because of their water draining and air logging capacity.



Clay soils are rich in humus and fertile. These soils are very good for wheat.

Deforestation causes soil erosion. Plant roots firmly bind soil. In the absence of plants, soil becomes loose. Wind and flowing water move the loose soil away. Soil erosion is severe in areas of little or no surface vegetation, such as deserts and barren lands. Therefore, cutting of trees and deforestation should be prevented, and efforts should be made to increase greenery.


6. Water Water : A Precious Resource

Nearly 71 percent of the earth is covered by water in the form of oceans, seas, lakes, rivers, ice, ground water and moisture in the air.

Nearly 71 percent of the earth is covered by water in the form of oceans, seas, lakes, rivers, ice, ground water and moisture in the air. However, most of it is not fit for human consumption. Water that is fit for human consumption is called freshwater. Only 0.006 percent of the water on the earth is actually available for our use. In nature, water exists in three forms: 

As a solid, it exists as icecaps at the poles, snow-covered mountains and glaciers.



As a liquid, it is in the form of water in oceans, lakes and rivers, and underground water.



Its gaseous form is the water vapour in the air around us. If you dig a hole in the ground, you'll reach moist soil at a certain depth. Soon, you'll reach a depth at which all space between the soil particles and cracks in the rocks are filled with water. The upper limit of this depth is called the water table. Rainwater and water from other sources, like rivers and ponds, seep through the soil. This water fills the empty spaces and cracks deep below the ground. This is known as infiltration. Sometimes, ground water accumulates between layers of hard rock. This is known as an aquifer. Water in aquifers can be drawn with tube wells and hand pumps. Plants use ground water and release it in the form of water vapour during transpiration. This completes the cycle of returning the water to the clouds. The clouds then release the water through precipitation, and the cycle starts all over again.


As long as the water drawn from the ground is replenished by seepage of rain water, the water table remains unaffected. The problem starts when we take more water from the ground than is replenished by natural means. Then the water table goes down, and it is said to have been depleted. Reasons for depletion of the water table:   

Increasing population that creates more demand for water. More wells are dug and water is drawn from them. Industrial activities are increasing the demand for water. For example, the construction industry uses tube wells to draw ground water.



An increase in agricultural activities demands more water. In areas where there are no streams and lakes, ground water is used for irrigation.



Scanty rainfall is another reason for depletion of the water table.



Water table depletion can be a result of deforestation, too. When trees are removed, the effective area for seepage reduces. It affects the replenishment of the water table. Water management is the continuous matching of water resources with the water requirements of a place.



Water management essentially involves activities that identify sources of water, prevent wastage of water, and implement recycling of water.



It may also include treatment of water to make it suitable for human consumption.



Prevent wastage of water



Water leaking from pipes



Leaking tap



Water over-flowing from buckets while clothes are being washed alongside



A person brushing teeth with the tap left running Conservation of water: Instead of letting rainwater run off into the sea, it can be used to recharge ground water. This is known as rainwater harvesting. Rainwater harvesting can be used to raise the water table in arid areas. It can also be used to create water storage areas. Farming, which typically requires huge quantities of water, can also benefit from VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Chemistry Chapter Notes Page 25

good water management. Drip irrigation is an economical way of using water. This technique involves the use of tubes to deliver water straight to the base of a plant, where it is taken up by the roots. Plants need water to absorb nutrients from the soil and make their food. Without water, plants would die, and greenery would be lost. This, in turn, would mean the end of all life on the earth, because without plants, there would be no food, oxygen or rainfall. There would also be many other problems.


VII I.I.T.Foundation, N.T.S.E.& Science Olympiad Biology Chapter Notes Biology Chapters as per NCERT Text Book

Topics

1.Nutrition in Plants

Nutrients in Plants

2.Nutrition in Animals

Digestion in Humans Digestion in Ruminants Digestion in Amoeba

3.Respiration in Organisms

Respiration Breathing

4.Transportation in Animals and Plants

Transportation in Humans Transportation in Plants

5.Reproduction in Plants

Sexual Reproduction in Plants Asexual Reproduction in Plants

6.Forests: Lifeline

Importance of Forest Introduction to Forest

7.Wastewater story

Water, Our Lifeline Water Treatment Importance of Sanitation

VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

Page 1

1. Nutrition in Plants Nutrients in Plants

Plants obtain their nutrition by various modes.

Plants obtain their nutrition by various modes. The mode of nutrition can be divided into four distinct types. Broadly speaking, plants can be divided into autotrophs and heterotrophs. Heterotrophic plants can be further divided into parasites, saprophytes and symbiotic plants. In plants, the green pigments called chlorophyll collect simple substances like water and salts from the soil and CO2 from the air, and using sunlight as a source of energy, convert the simple substances into complex food for the plant. This process is called photosynthesis. Leaves are the food factories of a plant. However, other parts of the plant play important roles, too. The roots absorb water and minerals from the soil. 

Photosynthesis takes place in the leaves.



The lower epidermis has openings called the stomata.



The stomata take in carbon dioxide from the air.



Chlorophyll captures energy from sunlight, and uses it to prepare food from carbon dioxide and water. The by-products are oxygen and water, which are released through the stomata during daytime. The food that has been made is sent to the other parts of the plant through the veins.


Page 2

All chlorophyll-containing plants, including algae, and some plants with red, brown or other dominant pigment, make food using this process. Thus, both sunlight and trees are essential to sustain life on Earth. As we saw, during photosynthesis, plants produce food in the form of glucose. This is then converted into complex compounds called carbohydrates, like starch and cellulose. Plants also prepare proteins with the help of nitrogen, which is obtained from the soil. Thus, the minerals dissolved in water are used to convert sugar into carbohydrates, proteins and fats. These food components form the source of energy for other heterotrophic plants and animals. The insectivorous mode of nutrition is observed in plants such as the pitcher plant and the Venus fly trap. 

Heterotrophic plants don't have chlorophyll, and are, therefore, unable to produce food using the process of photosynthesis.



They obtain food from other plants by following either a parasitic, saprophytic or some other form of symbiotic relation with them for food. Some plants, like the cuscuta, snatch food from other plants by climbing onto them. The plants on which they climb are called hosts. Since they deprive the host plant of valuable nutrients, the plant itself is called parasitic. Some plants obtain their nutrition from decaying organic matter. They secrete digestive juices onto dead and decaying matter, and then absorb the nutrients from it. This mode of nutrition is called saprtorophic nutrition. Plants that use the saprotrophic mode of nutrition are called saprotrophs. Plants get nitrogen from the soil by a mechanism of symbiosis.



A bacterium called rhozobium plays an important role in symbiotic nitrogen fixation.



This type of nitrogen fixation is observed in plants like peas, moong beans and other legumes.



By this process, both bacteria and plants get benefited mutually. o

We get nutrients from vegetables, fruits or meat.

o

We directly or indirectly depend on plants for our nourishment.

o

Plants that make their own food are called autotrophs.

o

Plants that depend on others plants for nourishment are called heterotrophs.


Page 3

o

Chlorophyll is the green pigment present in plants. Plants collect simple substances like water and salts from the soil and carbon dioxide from the air. Then, using sunlight as a source of energy, plants convert simple substances into complex food. This process is called photosynthesis.

o

The word photosynthesis is derived from two words - photo, meaning 'light', and synthesis, meaning 'to combine'.

o

Leaves are the food factories of a plant. The roots help by absorbing water and minerals from the soil. The stem or trunk helps by conducting water and minerals to the leaves. The actual process of photosynthesis takes place in the leaves.

o

The epidermis of the leaf is protected by a thin layer of cuticle.

o

The lower epidermis has openings called stomata, which aresurrounded by guard cells. The stomata take in carbon dioxide from the air.

o

The area above the lower epidermis is called the vein, which contains vessels to bring water and minerals to the leaf. Above this is a layer containing palisade cells that have green pigments, called chlorophyll, which capture energy from sunlight and use it to prepare food from carbon dioxide and water.

o

The by-products are oxygen and water, which are released through the stomata during daytime. The food is sent to other parts of the plant through the veins.

o

The sun and trees are called the lifeline of our planet.

o

During photosynthesis, plants produce food in the form of glucose, which is furtherconverted into complex compounds like starch and cellulose.

o

Plants also prepare proteins with the help of nitrogen, which is obtained from the soil. Microorganisms convert atmospheric nitrogen into water-soluble compounds, which are absorbed by the roots of plants.

o

The insectivorous mode of nutrition is seen in plants such as the pitcher plant and the Venus fly trap. Due to a lack of nutrients like nitrogen and other minerals in the soil, their leaves are modified to form a trap with hairy walls that can capture insects.

o

Once an insect enters the trap, the lid of the trap closes, and the prey gets entangled in the hair. The plant then digests its prey to obtain the required nutrients.

o

Heterotrophic plants do not have chlorophyll, and cannot produce food by photosynthesis.

o

The cuscuta plant derives valuable nutrients from the host plant, so it is called parasitic.

o

Fungi obtain their nutrition from dead and decaying organic matter. They secrete digestive juices onto dead and decaying matter, and then absorb the nutrients from it.


Page 4

o

Plants that use saprotrophic nutrition are called saprotrophs. The mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition.

o

Fungi reproduce using spores that germinate and grow into a new fungus.

o

Rhizobium bacteria form a symbiotic relationship with plants such as gram, peas, moong beans and other legumes.


Page 5

2. Nutrition in Animals Digestion in Humans

The human digestive system contains alimentary canal and associated glands.

The human digestive system contains alimentary canal and associated glands. Digestive system of man consists of Mouth, Buccal Cavity, Oesophagus, Pharynx, Stomach Duodenum, Small Intestine, Large Intestine (colon), Rectum and Anus. 

Mouth and Buccal Cavity is bounded by upper lip and lower lip.



Food is entered into the Buccal Cavity through mouth is called Ingestion.



The food is crushed and chewed in the Buccal Cavity with the help of the teeth and tongue.



The Buccal Cavity leads into pharynx.



The different teeth present in the Buccal Cavity are incisors, canines, premolars and molars. Salivary glands are present inside the Buccal Cavity.They secrete saliva. This saliva plays an important role in breaking down complex components like starch,which is further simplified into sugars.



A flap-like valve called the epiglottis closes the windpipe. It prevents the entry of food particles into tracheae.



Movement of food inside the esophagus in the stomach is by peristalsis movement.



Stomach is u-shaped and it is the widest part of the alimentary canal.


Page 6



Food is digested inside the stomach with the help of gastric juice secreted by the gastric glands present in the stomach. Liver is the largest gland in our body. It produces bile juice. Bile plays an important role in the digestion of fats.



Pancreas is the Mixed gland. It acts as a both endocrine and exocrine gland.



The pancreas secretes the pancreatic juice that helps to digest carbohydrates, proteins and fats. The pancreatic juice converts carbohydrates into simple sugars and glucose, proteins into amino acids, and the fats to fatty acids and glycerol. The inner walls of the small intestine have millions of small finger like projections called the Villi. Due to their presence the surface area for digestion as well as absorption of digested food increases by eight times.



Energy needed for various activities is obtained from glucose.



This process of utilisation of absorbed food, such as glucose, amino acids, fatty acids and glycerol is called as Assimilation. The undigested and unabsorbed food then enters the large intestine. The food then travels upward in the ascending colon of the large intestine. The function of the large intestine is to absorb the water and salts from the undigested food material. The undigested semi solid waste that passes into the Rectum is called faeces



It is then removed through the anus at intervals in a process called Egestion. o

The internal part of the mouth contains the teeth and the tongue. Each tooth is rooted in a separate socket in the gums.

o

The mouth, oesophagus, stomach, small intestine and large intestine form the alimentary canal, also known as the digestive tract.

o

The glands that secrete juices are the salivary glands, the gastric glands, the liver, the pancreas and the intestinal glands.

o

The digestive tract, along with the associated glands, forms the digestive system.

o

Bacteria in the mouth break down the sugars from leftover food, and release acids. The acids damage the teeth, causing tooth decay.


Page 7

o

The buccal cavity is bounded in the front by the upper and the lower lips, at the top by the roof of the mouth, at the bottom by the tongue, and on the sides by the cheeks.

o

Food is taken in through the mouth, a process known as ingestion.

o

Incisors act like scissors,and areused for biting food. Canines are sharp and pointed, and are used to pierce or tear food. Premolars and molars, or the principal grinders, help in chewing and grinding food.

o

The salivary glands secrete saliva, a transparent fluid that helps break down complex components into simpler forms.

o

The taste buds, located in different areas of the tongue, help detect different tastes.

o

The oesophagus is the food pipe that carries food from the throat to the stomach. The oesophagus is also known as the gullet, and is about 25 centimetres long.

o

When you swallow food, a flap-like valve, called the epiglottis, closes the windpipe.

o

The stomach is the widest part of the alimentary canal. Its walls are thick and very muscular. It is closed off at each end by a ring of muscular valves.

o

Digestion in the stomach occurs with the aid of hydrochloric acid, mucous and digestive juices.

o

The 'C' shaped tunnel, called the duodenum, is the upper part of the small intestine.

o

The liver secretes a yellowish green watery fluid called bile. It is temporarily stored in a sac called the gall bladder. It has a narrow tube-like structure called the bile duct, which opens into the duodenum.

o

The pancreas secretes pancreatic juice that helps digest carbohydrates, proteins and fats. The pancreatic juice converts carbohydrates into simple sugars, glucose and proteins into amino acids, and fats into fatty acids and glycerol.

o

Bile breaks the larger fat molecules into tiny droplets, thereby increasing their surface area, which helps digest fats easily.

o

The pancreatic duct that arises from the pancreas joins the bile duct.

o

The inner walls of the small intestine have millions of small finger-like projections, called the villi. The surface of the villi allows amino acids and glucose to reach the blood capillaries, and allow fatty acids and glycerol to reach the lymph vessels, a process called absorption.

o

The process of utilisation of absorbed food such as glucose, amino acids, fatty acids and glycerol is known as assimilation.

o

Undigested food, which contains a lot of water and salts, is absorbed by the walls of the large intestine.


Page 8

o

Food travels upwards in the ascending colon of the large intestine, then moves towards the transverse colon, and then back downwards towards the descending colon.

o

The undigested semi-solid waste that passes into the rectum is called faeces. Faeces are temporarily stored in the rectum, and are removed through the anus at intervals by a process called egestion.

Digestion in Ruminants

Cellulose is an important component in the diet of herbivorous animals. Cellulose is an important component in the diet of herbivorous animals. It is present in the cell wall of plant cells. Humans cannot digest cellulose. Grass eating animals like the cow, ox, buffalo and sheep swallow the food without chewing. After feeding, they bring the food from the stomach back into the mouth and chew it leisurely. This process is called rumination, and such animals are called ruminants. 

The stomach of a ruminant is divided into four chambers - the rumen, reticulum, omasum and abomasums. Among these, the rumen is the largest.



The partially digested food in the rumen is called cud.



Micro-organisms present in the stomach of the cow help digest the cellulose.



Digestion in ruminants Grass-eating animals like cows, sheep, buffaloes and goats do not chew their food properly. Instead, they swallow it quickly and store it in the rumen. In the rumen, the digestive juices partially digest the food. The partially digested food in the rumen is called cud. Partially chewed food is pushed down through the oesophagus into the rumen.


Page 9

The cud is brought back to the mouth to be chewed properly. The process of chewing cud is called rumination. Rumination is also called second chewing. Animals that partially digest food in the rumen and bring it back to the mouth for additional chewing of the cud are called ruminants. A large sac-like structure, called the caecum, lies between the small and large intestines. Ruminants have green plants as their food. These plants contain a type of complex carbohydrate, called cellulose. In the caecum, a kind of symbiotic bacteria helps digest cellulose. In ruminants, a major part of all carbohydrates, including the complex carbohydrates such as cellulose and hemi-cellulose, is digested by bacterial action. These symbiotic bacteria are not present in the human digestive system. That is why humans cannot digest cellulose.

Digestion in Amoeba

The amoeba is a microscopic unicellular organism. The amoeba is a microscopic unicellular organism. It is belongs to the group protozoa. The name comes from the Greek word amoibe, meaning change. The habitat of the amoeba is fresh water. The amoeba contains jelly-like cytoplasm. Inside the cytoplasm are cell organelles like the nucleus, food vacuoles and contractile vacuole. An amoeba takes in oxygen gives off carbon dioxide through the cell membrane by a mechanism of diffusion. It takes in oxygen dissolved in water. An amoeba can move all directions and can change its shape with the help of pseudopodia as a locomotary organ. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

Page 10

An amoeba engulfs its prey along with a droplet of water with the help of pseudopodia, and then forms a food vacuole inside the cytoplasm. The prey can be killed and digested with the help of the digestive juice secreted by the food vacuole. The undigested food is thrown out by changing the shape of the body. Amoeba forms a cyst in unfavourable conditions. The term amoeba is derived from the Greek word amoibè, meaning change. The amoeba is one of the simplest, jelly-like animal ... the ultimate shape shifter. An amoeba is so minute that it can be seen only under a microscope. The amoeba belongs to the group Protozoa. Amoebae are found at the bottom of fresh water bodies like ponds and lakes, even in a gutter or muddy water. Some of them are also found in damp soil and food. The amoeba is a single-celled animal. The amoeba has a jelly-like substance, called the cytoplasm, inside a flexible boundary called the cell membrane. Floating in the cytoplasm are various structures like the nucleus, food vacuoles and contractile vacuoles. An amoeba takes in dissolved oxygen from the surrounding water, and gives off carbon dioxide into the water through the cell membrane. An amoeba can move in all directions using temporary feet-like structures, called pseudopodia. An amoeba, with the help of pseudopodia, captures and engulfs its prey along with a droplet of water. In an amoeba, digestive juices convert food particles into simpler substances. The cytoplasm absorbs digested food directly, and uses it for growth, maintenance and multiplication. In the amoeba, undigested remains of food are thrown out of the body. An amoeba roll into a tiny ball called cyst during unfavourable conditions.


Page 11

3. Respiration in Organisms Respiration

The cells in our body perform functions like growth, excretion, reproduction, etc..

The cells in our body perform functions like growth, excretion, reproduction, etc. A cell needs energy to perform these functions. The food we take in is converted into glucose by the digestive system. 

Glucose reaches the cells through the blood. In the presence of oxygen, glucose is broken down into energy, water and carbon dioxide. Anaerobic respiration takes place in the muscle cells if enough oxygen is not present in the cell. Glucose is converted into lactic acid and carbon dioxide in the absence of oxygen. Accumulation of lactic acid inside the cells leads to muscle cramps. Oxygen will break down lactic acid into carbon dioxide and water.



Yeast respires in the absence of oxygen. Glucose is converted into alcohol and carbon dioxide by yeast in the absence of oxygen. Yeast is used in beverage industries to produce beer and wine. During day time, plants utilise oxygen to perform photosynthesis. During the night, plants release carbon dioxide and take in oxygen for respiration. In plants, the exchange of gases takes place through a special structure, called the stomata. The process of respiration in plants breaks down glucose and releases energy.


Page 12

The energy released from food is useful in activities like growth, excretion, reproduction, running, reading and sleeping. The food we eat has to be converted into glucose for releasing energy. Digestive juices convert complex carbohydrates into glucose. The breakdown of glucose in a cell to release energy is called cellular respiration. Blood absorbs glucose and transports it to the cells. In the cells, this glucose is broken down to release energy. The breakdown of glucose in the presence of oxygen is called aerobic respiration. Cells use oxygen to break down glucose and release energy. When we inhale air, oxygen goes into the lungs. From the lungs, the oxygen is absorbed by the red blood cells and supplied to all the cells in the body. Our cells use this oxygen to break down glucose to release energy. Carbon dioxide and water are also formed. The breakdown of glucose in the cell in the absence of oxygen is called anaerobic respiration. Muscle cells require a lot of energy to perform exercises. Muscle cramps occur when strenuous exercises like cycling, running, speed walking, etc. are done for a long time. The accumulation of lactic acid in the muscles causes muscle cramps. During anaerobic respiration, lactic acid is formed in the muscles. A massage or a hot bath can ease a muscle cramp by improving the circulation of blood in the affected muscles. Anaerobic respiration can be seen in yeast. The breakdown of glucose in the absence of oxygen in yeast forms alcohol, energy and carbon dioxide. Yeasts and other organisms that respire in the absence of oxygen are also known as anaerobes. Plants utilise oxygen for respiration released through photosynthesis during the day, and at night, they take in oxygen from the atmosphere and give out carbon dioxide and water vapour. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

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The stomata are involved in the entry and exit of gases in plants.

Breathing

The cells of living organisms require a constant supply of oxygen to release energy. The cells of living organisms require a constant supply of oxygen to release energy. This is done by a process called breathing. Breathing involves two steps - one inhalation and one exhalation. The breath rate of human beings is 15 - 18 breaths a minute. Air passes through the tiny hair in the nasal cavity, and then through the pharynx, larynx and windpipe before reaching the lungs. The hairs in the nasal cavity prevent the entry of dust particles and pollen. The mucous lining is present from the nasal cavity to the lungs. Lungs are situated inside the chest cavity, and they rest on a large muscular sheet called the diaphragm, which forms the floor of the chest cavity. When you breathe in, your diaphragm and rib cage get into action. The diaphragm is protected by the rib cage. The diaphragm plays an important role in inhalation and exhalation. An insect does not have any respiratory organs. For respiration, they have special organs called spiracles. Oxygen reaches to the cells directly through the spiracles by means of diffusion. The skin is the respiratory organ in animals like frogs and earthworms. The skin in these animals is moist and slimy, which makes it easier for oxygen to diffuse in and carbon dioxide to diffuse out of the body. However, frogs are special animals. They can breathe through their skin in water, while on land they can breathe through their skin as well as their lungs. The respiratory organs in fish are the gills. Fishes take in oxygen in dissolved form. During respiration, water enters the body through the mouth, and then passes through the gills and comes out of the operculum. The gills take in the oxygen dissolved in the water and give out carbon dioxide.


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Breathing is a mechanical process that involves two steps - taking in oxygen from the air and giving out carbon dioxide to the air. The action of taking in air rich in oxygen is termed as inhalation. The action of giving out air rich in carbon dioxide is called exhalation. One inhalation and one exhalation make up one breath. The number of times you breathe in one minute is called the breathing rate. After air enters the nostrils, it passes through the nasal cavity, where tiny hair present inside the cavity trap unwanted particles such as smoke, dust and pollen. From the nasal cavity, air travels through the pharynx, larynx, and windpipe before it reaches the lungs located in the chest cavity. The lungs rest on a large muscular sheet, called the diaphragm, which forms the floor of the chest cavity. When inhaling, the rib cage moves outwards, and the diaphragm contracts and moves downwards. The rib cage expands and this increases the space in the chest cavity. Air rich in oxygen is pulled into the lungs.


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4. Transportation in Animals and Plants Transportation in Humans

All livings beings need food, water and oxygen for survival and to perform various activities.

All livings beings need food, water and oxygen for survival and to perform various activities. Food gets digested in the food canal or in the alimentary canal. The nutrients are transported from there to other parts of the body in the form of glucose, amino acids, fats, etc. This function is performed by the circulatory system. Unwanted harmful substances and excess water in the body cells are removed by the excretory system. Circulatory System This is also known as the cardiovascular system. It consists of the heart, blood vessels and blood. Functions of the Circulatory System Blood helps transport food, water and oxygen to all parts of the body. The fluid part of blood is known as plasma.


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Blood consists of three types of cells Red Blood Cells These cells perform a specific function. Red blood cells, also called RBCs, have iron pigments known as haemoglobin that combines with oxygen and transports it to all parts of the body. The presence of haemoglobin gives red colour to blood. On an average, there are five million RBCs per cubic mm of blood. White Blood Cells White blood cells, or WBCs, defend the body against infections. Platelets When a blood vessel is cut, blood comes out immediately. After some time, a dark red clot is formed on the cut. This is formed by cells called platelets in blood. When the platelet count decreases, excessive bleeding takes place and may even cause death. Blood Vessels Blood flows through narrow pipe-like structures in the body, known as blood vessels. These blood vessels transport food, oxygen and waste within the body. Blood vessels are of two types Arteries transport oxygen-rich blood from the heart to the other parts of the body. The blood in the arteries is bright red in colour. Blood flows through the arteries at high pressure, because of which the arteries have thick elastic walls. When an artery is cut, blood rushes out immediately. The arteries divide into smaller vessels when they enter an organ, and further divide into thin tubes called capillaries. These capillaries supply oxygen and nutrients to the tissues and also collect waste and carbon dioxide.


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Veins carry blood low in oxygen content. Veins have valves that allow blood to flow in one direction towards the heart - only. Veins have thin walls. That is why when a vein is cut blood comes out slowly and continuously. A number of capillaries together form a vein. Heart The heart pumps blood through our body. It is located in the chest cavity with its lower parts towards the left. Its size is that of the person's fist. The pumps blood rich in carbon dioxide to the lungs, and oxygen-rich blood to the other parts of the body. It also prevents blood rich in oxygen from mixing with blood rich in carbon dioxide. It has four chambers. The two upper chambers are the atria and the two lower chambers are the ventricles. The partition between the two chambers is called the septum. Blood rich in oxygen is pumped out from the left ventricle to all parts of the body. Blood rich in carbon dioxide is pumped out from the right ventricle to the lungs through the pulmonary artery. It is the only artery in the human body that carries carbon dioxide-rich blood. The pulmonary vein is the only vein in the body that carries oxygen-rich blood. The walls of the heart are made up of the most powerful muscles. The muscles of the heart contract and relax, which constitutes a heartbeat. The device that amplifies the sound of a person's heart beat is called a stethoscope and consists of a chest piece that holds a sensitive diaphragm. The flow of blood in an artery over a bone is called the pulse. The normal pulse rate is 70 to 80 per minute. Excretory System The cells in the body perform various activities. Waste products such as urea, uric acid and excess water are formed and have to be removed from the body. The removal of waste products is termed excretion. The organs that help in the process of excretion constitute the excretory system, and include the kidneys, the ureters, the urinary bladder and the urethra. The useful and harmful substances in blood enter the kidneys, where the capillaries filter it. The useful substances are reabsorbed, but the harmful substances are removed along with water in the form of urine. The urine from the kidneys comes down through long tubes called the ureters, which open into the urinary bladder where the urine is stored temporarily. When the bladder fills, the urine is disposed.


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The functioning of the kidneys stops when there is an infection. This is known as kidney failure. As a result, waste products remain in the blood. When blood is not filtered, survival becomes difficult, so it is filtered through an artificial kidney. The process is called dialysis. The artificial kidney is called a dialysis machine. Sweat is an excretory product and it consists of water and salt. Sweat cools the body and it helps to maintain normal temperature. The circulatory system helps in the transport of glucose, amino acids and fats to different parts of the body. The removal of waste from the body is carried out by the excretory system. The circulatory system is also known as the cardiovascular system. The cardiovascular system consists of the heart, blood vessels and blood. Blood helps transport food, water and oxygen to all parts of the body. It also helps transport harmful and unwanted waste to the excretory organs. The fluid part of blood is plasma. Blood consists of red blood cells, white blood cells and platelets. Each of these cells performs a specific function. Red blood cells transport oxygen to different parts of the body. Red blood cells have an iron pigment called haemoglobin that combines with oxygen, and transports the oxygen to all parts of the body. The presence of haemoglobin gives blood its red colour. White blood cells or WBC's defend the body against infections. Whenever there is a cut or a wound, a clot is formed by cells called platelets present in blood. Blood flows through narrow pipe-like structures, known as blood vessels. These blood vessels transport food, oxygen and waste within the body. Arteries have thick elastic walls and transport bright red oxygen-rich blood from the heart to the other parts of the body. Veins have valves on their inner lining that allow blood to flow only in one direction. They carry carbon dioxide-rich blood to the heart from different parts of the body. Arteries divide into fine vessels or tubes known as capillaries. A number of capillaries join together to form a vein. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

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Blood capillaries distribute oxygen and nutrients to tissues. The heart is located in the chest cavity, and pumps blood throughout the body. The heart consists of four chambers. The two upper chambers of the heart are known as the atria. The lower two chambers of the heart are the ventricles. The walls of the heart are made up of the most powerful muscles. Their rhythmic contraction and relaxation constitute heartbeats. Heartbeat can be recognised by placing the palm on the left side of the chest. The stethoscope is a device that amplifies the sound of your heartbeat. The pressure applied by blood on the walls of an artery at a particular part is the pulse. The number of times the heart beats in a minute is the same as the pulse rate. The best place to check pulse rate is the wrist. The ideal pulse rate is 70 to 80 per minute. The process of the removal of waste produced in the cells in living organisms is called excretion. The organs that help in the process of excretion constitute the excretory system. The excretory system consists of the kidneys, the ureters, the urinary bladder and the urethra. The kidneys are the major organs of the excretory system. Urine trickles down from the kidneys into the urinary bladder through tubes called the ureters. Urine consists of 95 per cent water, and a small percentage of urea and other waste products. The ureters open into the urinary bladder. The urinary bladder stores urine temporarily. Urine is expelled through the urethra. Waste substances are removed from the body in the form of urine. Blood is carried through blood capillaries to the kidneys for filtration. Sweat is also an excretory product released from the body. It contains water and salts. Sweating helps maintain the temperature of your body.


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The impairment of the functioning of the kidneys is known as kidney failure. The filtration of blood regularly by a kidney machine is known as dialysis, and the dialysis machine is also known as an artificial kidney.

Transportation in Plants

Plants make their own food by taking in carbon dioxide from the air, minerals and water from the soil.

Plants make their own food by taking in carbon dioxide from the air, minerals and water from the soil. They release oxygen and water vapour, and the process is termed photosynthesis. Plants get energy from the food to perform the vital activities. Food and water is transported to various cells in the body. The transportation process Root hair Plants take in water through their roots. All roots have a root cap to protect the tender root tip from getting damaged by the soil particles. When the plants grow, the roots branch and rebranch and get fixed in the soil. At the roots tips, there are a large number of cells that absorb water and nutrients from the soil. The amount of water absorbed is proportionate to the number of root hairs. As the number of root hair increases, the surface area also increases, and the plant absorbs more water and minerals.


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Xylem and phloem There are pipe-like vessels in plants through which water and minerals enter. Each vessel is made up of thick walls and elongated cells. A tissue is a group of cells that performs a specialised function in organisms. These are commonly known as conducting tissue. The conducting tissues are of two types. They are xylem and phloem. These tissues form a continuous network within the plants, and spread across the roots, stem, branches and leaves. The xylem carries water and nutrient minerals from the roots to the leaves. The phloem carries food from the leaves to various parts of the plant. Transportation process - An example: The functioning of cells in potato: Peel a potato, cut it into two pieces and slice its bottom Make a deep hole on the top part of the potato and make a potato cup. Put some sugar solution in the cup. Make a note of the level of the sugar. Pierce the outer wall of the potato with a pin. Place the potato in a container with water in such a way that it is partly immersed in water. Leave it undisturbed for some time. Now observe that the level of the sugar solution increases. This is because water moves from glass beaker (low concentration) to potato (high concentration). Transpiration process By the force of suction, water and nutrients are transported to all parts of a plant. Water and minerals reach the leaves and use only a small amount to make food. There are small pores, called the stomata, on the lower surface of the leaves through which excess water is released in the form of water vapour. The process of releasing water vapour from the leaves into the atmosphere through the stomata is called transpiration. Transpiration increases the moisture content in the atmosphere and cools the surroundings. Suction develops in the plant when water from the leaves is lost in the form of water vapour. This force is used to absorb more water and minerals. The suction force is also known as the transpiration pull. It is strong enough to draw water even in tall trees. Plants synthesise their food using water, minerals and carbon dioxide in the presence of sunlight, and give out oxygen, through a process called photosynthesis.


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Plants take in water through their roots from the soil. The tender root tips are protected by root caps. They protect the root tip from getting damaged by the soil particles. Roots have single-celled root hair to absorb water and minerals from the soil. The amount of water absorbed is proportionate to the number of root hair. Water and minerals reach different parts of the plant through pipe-like vessels. Each vessel is made up of thick-walled, elongated cells, known as conducting tissue. A tissue is a group of cells that perform a specialised function in an organism. The xylem and phloem constitute the vascular tissue. These tissues form a continuous network that is spread across the roots, stem, branches and the leaves of the plant. The xylem carries water and minerals from the roots to the leaves. The phloem transports food from the leaves to various parts of a plant's body. Water reaches the xylem vessels of the root through the cells. Water and minerals are transported to various parts of a plant by a suction force. The process of releasing water vapour through the stomata into the atmosphere is known as transpiration. The excess water in the form of water vapour is given off through these pores. Transpiration increases the moisture content of the atmosphere, thus bringing about a cooling effect in the immediate surroundings. The force used by plants to absorb more water and minerals from the soil is known as the transpiration pull. The suction force is also known as the transpiration pull.


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5. Reproduction in Plants Sexual Reproduction in Plants

The process of producing young ones that look like the parents is called reproduction.

The process of producing young ones that look like the parents is called reproduction. Plants reproduce either sexually or asexually. Plants reproduce sexually by the most attractive part, called the flower. 

The stalk of a flower is called the pedicel.



All floral parts are arranged on its flattened tip, called the receptacle.



The stamens and the pistil are the reproductive parts of a flower.



The anther contains pollen sacs that produce pollen grains.



Pollens are the male reproductive unit of the flower.



Pistil is the female reproductive part of the flower.



Bisexual flowers contain both - the stamens and the pistil. For example, mustard and rose.



Unisexual flowers have either the stamens or the pistil. For example, cucumber, maize and watermelon. The transfer of pollen grains from one flower to another is called pollination. Pollen grains transfer from one flower to another by pollinating agents The transfer of pollen grains from the anther of one flower, to the stigma of another flower on another plant of the same type, is known as cross-pollination. The transfer of pollen grains from the anther to the stigma of the same flower or to the stigma of VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

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another flower on the same plant, it is termed self-pollination. The zygote is formed by the fusion of the male and female gametes. This process is called fertilisation. After fertilisation, the ovary changes into a fruit. It may be either fleshy or dry. Seeds and fruits are dispersed by agents like wind, water, animals and humans. The pods present in these seeds dry up in the sun. This causes the pod to split with great force, thereby dispersing the seeds away from the parent plant. Some seeds are dispersed by a special method called explosion. Examples are mustard, ladies finger, peas, bean, pod and castor. The process by which all living things produce young ones that look like themselves is called reproduction. Plants reproduce either sexually or asexually. Flowers are the most attractive and the reproductive parts of a plant. A flower may have a stalklike structure, called the pedicel. The sepals, petals, stamens and the pistil are arranged on its flattened tip, called the receptacle. The stamens are the male reproductive parts. The pistil is the female reproductive part. The pistil produces gametes. Gametes are the reproductive cells. The anther is a knob-like structure of the stamen. The filament is the long part of the stamen. The anther contains pollen sacs, which produce pollen grains. Pollen grains are yellow powdery particles containing the male gametes or the male reproductive cells. The number of stamens in a flower are three or five, or in multiples of three of five. The ovary contains numerous ovules. Each ovule contains a female gamete or egg cell. The basal swollen part of the pistil is the ovary.


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The pistil is the centrally located female reproductive part of a flower. The stigma and the style are major parts of the pistil. A flower with a stamen and a pistil is a bisexual flower. A flower that has either a stamen or a pistil is a unisexual flower. Pollen grains from the stamen fall on the stigma for reproduction to take place. The transfer of pollen from the stamen to the stigma is known as pollination. The transfer of pollen from the stamen to the stigma of the same flower is called selfpollination. The transfer of pollen from the stamen of one flower to the stigma of another is called crosspollination. A zygote is formed by the fusion of a male gamete and a female gamete. After fertilisation, the zygote develops into an embryo. The ovule develops into a seed. The seeds of the coconut tree fall into water when they ripen. The pond iris is adapted for seed dispersal through water. Seed dispersal is a method of dispersal of seeds through water, animals, birds, wind or insects. Bursting is also a method to disperse seeds, found in balsam. Xanthium fruits have spines to get attached to the fur of animals or clothes. Drumstick seeds are dispersed by the explosion of fruits.


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Asexual Reproduction in Plants

Reproduction is mainly of two types sexual and asexual.

Reproduction is mainly of two types - sexual and asexual. In sexual reproduction, the male and the female gametes fuse to form seeds that eventually develop into new plants. The seeds are formed inside the fruit. On the other hand, in asexual reproduction, a new plant is grown from any part of a plant other than the seeds. There are different methods by which plants reproduce asexually. They are vegetative propagation, budding, fragmentation and spore formation. The vegetative parts of a plant are the roots, stems and leaves. When new plants are produced from these parts, the process is called vegetative propagation. 

A new rose plant can be grown by cutting off a part of the stem of an existing plant, with two or more nodes, and planting it in the ground.



A node is a part of the stem from where a leaf grows.



This stem grows into a new rose plant. These are the buds of a bryophyllum plant. This plant has buds on the edges of its leaves. When the buds come in contact with moist soil, each bud is capable of growing into a new plant. Plants that use buds for vegetative propagation are potato, ginger and turmeric, amongst others. Roots that store food are known as tubers. Such roots are the food storage tanks for the plants.



When these tubers are detached from the parent plant and planted in the soil, they grow into a new plant.



A plant that grows from a single root tuber, and then branches and rebranches, thereby covering a large area. VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

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

A number of root tubers are produced by a single plant.



Another plant that is grown from the tuber is the dahlia plant. An ingredient used to bake a cake is a single celled plant known as yeast. Yeast reproduces by a process called budding. The small bulb-like projection coming out from the yeast is known as a bud. It detaches from the parent plant and develops into a new plant. Algae, the simplest green plants, reproduce by an asexual method known as fragmentation. An alga breaks up into smaller fragments. Each of these smaller fragments grows into a new independent alga. The white mass and cottony like structure on the bread is called mould.



It is a type of fungus that grows on moist organic surfaces like leather shoes and moist walls. This fungus reproduces by the means of spores.



They can survive in extreme conditions like high temperature and low humidity.



Ferns and moss are the example of the spore type of asexual reproduction. o

Placing seeds on or in the ground for future growth is called sowing.

o

There are several ways by which plants produce offspring (young ones). These are mainly divided into two types - sexual and asexual. The sexual mode of reproduction involves the fusion of the male and the female gametes to form seeds that eventually develop into new plants. In the asexual mode of reproduction, a new plant is grown from a part of the plant other than the seeds.

o

There are different methods by which plants reproduce asexually. These are vegetative propagation, budding, fragmentation and spore formation.

o

Roots, stems and leaves are called the vegetative parts of a plant. When new plants are produced from these vegetative parts, the process is called vegetative propagation.

o

Bryophyllum propagates vegetatively by the formation of leaf buds on the margins of a leaf. When the buds come in contact with moist soil, each bud is capable of growing into a new plant.

o

Sweet potato and dhalia are capable of producing young ones from their roots.

o

Yeast reproduces by a process called budding. A small bulb-like projection that comes out from the yeast is known as a bud. This bud grows and detaches itself from the parent cell, and then grows independently as a new plant.


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o

Yeast is used to bake a cake and to make dough. During budding, yeast respires and releases carbon dioxide. The carbon dioxide released helps the dough to puff up and become spongy.

o

Algae are green, thread-like plants and grow in stagnant water, ponds and lakes. They float on the surface of the water.

o

Algae reproduce by a method known as fragmentation. The breaking down of filaments into fragments that grow into young ones is called fragmentation.

o

Ferns reproduce by releasing spores that germinate into young ones.

o

The cotton-like white mass on bread formed by fungus is called a mould. It is a type of fungus that grows on moist organic surfaces like leather shoes, moist walls, etc.

o

Fungus reproduces by means of spores. Spores are covered by a protective hard coat.

o

Spores can survive in extreme conditions like high temperature and low humidity because of the protective hard coat.

o

Moss also reproduces by spores


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6. Forests: Lifeline Introduction to Forest

These forests have given Kerala its healing touch in the form of Ayurvedic medicines

Kerala, which is one of the India's southern states, is also known as "God's own country". It is rich in natural vegetation. The forests are spread over a large area, and consist of tropical wet evergreen, partly evergreen, deciduous and dry forests.

Some plants found in these forests are known for their medicinal value. These forests have given Kerala its healing touch in the form of Ayurvedic medicines for the treatment of various ailments. Endemic species When an animal or a plant is found in a specific area, it is known as an endemic species. Wayanad Wildlife Forest It's a large collection of flora and fauna. Many endemic species of animals, such as pale-faced monkeys called bonnet macaques, striped-neck mongoose, small Indian civet, striped hyena, jackal, Indian fox, wild bear, giant squirrel, bison, chital and others, are found here.

Kerala's forests have huge Neem trees that can grow up to a height of 50 to 65 feet. The Neem tree has high medicinal value and is said to treat around 40 diseases. The wood of the Neem tree is used to make a musical instrument, called the dhol.


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Trees such as the bamboo, which can grow at the rate of 45 inches in a day, the fig tree, the amla tree or the Indian gooseberry, the Sal tree or the sandal wood tree, the teak tree and many more are all found in these forests. The crown, i.e. the branchy part of a tree above the stem, is not of the same type and size for all the trees. So they appear like different layers in the forest and are known as under storey.

Apart from all these trees, the forest is covered with shrubs, herbs, tall grasses, creepers and climbers. The branches of the tall trees are just like a roof over the other plants, and are called the canopy. The soil of the forest is moist and warm because it is covered with leaves and fruits. The floor of the forest is a soft spongy carpet laid with dry leaves. Dead and decaying leaves, fruits and herbs produce a black substance called humus, which is good for the growth of the plants. Saprophytic organisms and micro-organisms convert the dead waste into humus.

Plants are called producers because they prepare their own food. These producers are eaten by animals that are the primary consumers, which are, in turn, eaten by other animals that are the secondary consumers. Finally, the secondary consumers are eaten by the tertiary consumers. Thus, forests play a very important role in the food chain. When forests are affected, they affect living beings such as animals and plants.

Importance of Forest

Forests play a vital role in the preservation of the water cycle.

Forests play a vital role in the preservation of the water cycle. Plants absorb water from the ground through their roots. Excess water from the plants is released into the atmosphere in the form of water vapour. This process is termed as transpiration. Plants release a huge amount of VII I.I.T.Foundation, N.T.S.E. & Science Olympiad Biology Chapter Notes

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water into the atmosphere through transpiration. A single apple tree looses as much as 30 litres of water in a day. The water vapour rises in the atmosphere and condenses to form clouds. The clouds move to the land due to sea breeze and bring rain. This is called precipitation. Excess water seeps into the ground and reaches the ground water table. By the process of transpiration and photosynthesis, forests maintain the temperature. During photosynthesis, plants take in

to prepare food, and release

and water vapour into the

atmosphere. The more the number of trees, the more the oxygen; and the less the number of trees, the more the carbon dioxide in the atmosphere. A decrease in the number of trees results in global warming. Trees are the main source of oxygen. Advantages of forests Forests provide shelter for the animals and act as a protective camouflage. Forests provide shelter and food to the tribes living in the jungle. Forest trees such as the bamboo are used in making furniture, baskets, ladders, etc. The teak tree is used to make furniture. The Neem tree is used for medicinal purposes. Forests also provide wood to make paper and other products such as gum, wax, rubber, and honey. There are major benefits from forests and so they should be protected. Deforestation Due to the rise in the population, trees are being cut down to obtain land for agriculture, industry and housing. This is known as deforestation. Due to this, many species become homeless. Forests are also lost due to forest fires and floods. If trees are cut down, then the carbon dioxide level increases. This leads to an increase in the temperature of the earth's surface, resulting in global warming. If forests disappear, then the soil becomes very loose, resulting in soil erosion. The fertility of the soil is maintained when the roots hold the trees and prevent soil erosion by wind and water.


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7. Wastewater story Water, Our Lifeline

We use water every day for various purposes.

We use water every day for various purposes. Water should be filtered before it is used for drinking as it contains many impurities that cannot be easily seen with the naked eye. In order to have safe drinking water, it should be boiled. Water gets contaminated by humans and it is not safe for drinking. Drinking contaminated water results in diseases such as cholera, typhoid and diarrhoea. Polluted water can also prove fatal. Water gets contaminated and scarcity of clean water is due to the following reasons: 

People take baths and wash clothes in rivers and lakes.



Many people bathe their animals in rivers and lakes.



Increase in the population, industries and improper disposal of waste. Water has become so scarce that many people have to travel several kilometres to get drinking water. March 22nd is celebrated as World Water Day. It was on March 22, 2005, that the United Nations declared 2005-2015 as the International Decade for the Action "Water for Life". Clean water is needed not only for drinking, but also for cooking, washing and bathing. A lot of waste water is produced at homes, which should be cleaned before it drains into rivers or lakes and also before it is reused.


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Process of Cleaning Water Pollutants in waste water can be removed in several stages, and this process is called "sewage treatment". Waste water released from homes, industries, hospitals and offices, and water collected during rains from roof tops or streets, is collectively termed Sewage. This sewage is liquid waste containing dissolved impurities, and the impurities are called contaminants, which contain many harmful substances. Sewage contains: Organic and inorganic impurities Organic impurities in sewage include animal waste, urine, oil, vegetable and fruit waste, faeces, pesticides and herbicides. Inorganic impurities include phosphates, nitrates and metals. Disease-causing bacteria There are disease-causing bacteria in sewage. Saprotrophic bacteria These are bacteria that feed on dead organisms. Nutrients Sewage contains some useful nutrients, such as phosphorus and nitrogen. Other microbes Microbes that cause typhoid, cholera, diarrhoea and dysentery are present in sewage. Types of Sewages There are various types of sewage, depending upon its colour and odour. Some sewage is black and has a very bad odour.


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Sullage water Waste water released from the kitchen is called sullage water. The contaminants in sullage water are mild detergents, oils and food particles. Moreover, it contains lots of water released when utensils are washed. Foul waste Waste water released from toilets is termed as foul waste. It consists of human waste and a lot of bacteria that release gases and bad odour. It is highly infectious. Trade waste Waste released from industries and commercial organisations is called trade waste. It consists of acids and strong chemicals that are toxic in nature. Sewerage The network of small and big pipes that carry wastewater is called sewers, and all sewers together form the sewerage. Wastewater is carried from home to the point of disposal, that is, the wastewater or sewage treatment plant. After treatment of wastewater, the clean water is released into nearby water bodies. Sewerage has manholes that can be used to clear blockages. Manholes are located every 50 to 60 metres in the sewerage. If there is no sewage facility, then waste water is directly drained into nearby streams and lakes, which results in water contamination.


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Water Treatment

Waste water needs to be treated before it can be reused, or released into a water body.

Waste water needs to be treated before it can be reused, or released into a water body. Wastewater has many impurities and these impurities should be removed by water treatment. Waste water from households is treated at a treatment plant to remove the physical, biological and chemical matter. In the physical process, waste water is filtered to remove large impurities. For example: Take a funnel. Place a filter paper in the funnel and wet it with water. Then add some sand, fine gravel and medium gravel into the funnel. These are layers for the filtration of water. Now pour wastewater into the funnel and collect clean water. Repeat the same process several times till the collected water looks clean. In water treatment plants, the layers are substituted by: Bar Screens Bar screens are screens that prevent the flow of large objects in wastewater. These screens help to remove large objects like rags, plastic bags, cans, napkins and sticks from sewage. These bar screens are cleaned regularly either manually or with the help of the machines. Grit and sand removal tank The grit and sand removal tank may not remove some impurities, such as faeces.


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Clarifier A clarifier is a tank with its central part inclined downwards so as to allow faeces to settle down. The inclined waste is then removed using a scraper. This waste is termed as sludge. Sludge is transferred to a separate tank where it is decomposed using bacteria. The gas produced is burned in an apparatus such as micro-turbine to generate electricity. Finally, a skimmer is used to remove the oils and grease. Thus, if all the physical contaminates are separated from the sewage, then the sewage is termed to be clarified water. Biological contaminates such as bacteria and microbes consume human waste, food waste, soaps and other wastes, and still remain in the clarified water. Now this clarified water is passed into an aerator in waste water treatment. An aerator pumps air into the water. After many hours, the bacteria settles at the bottom of the tank as activated sludge. The water present in the top is 95% clean and is let out into a water source, while the activated sludge is dried in a sand bed and is used as manure. In the chemical process, take a chlorine tablet and put it in a beaker full of water. Observe that water is clean when the tablet dissolves. That is why chlorine tablets or ozone is used to disinfect water in treatment plants. Different mechanisms were used to treat water, even in the olden days. The ancient Greek and Indian writings dating back to as early as 2000 BC recommended water treatment methods. People knew about water treatment procedures back in 2000 BC. The Egyptians discovered the process of coagulation for water treatment. Eucalyptus trees are planted along the sewage ponds in which water is released after water treatment processes. Eucalyptus trees absorb wastewater from the pond and release pure water vapour into the atmosphere. Oils and fats can harden and block water pipes. Fats clog the soil pores in an open drain, reducing the effectiveness of filtration of water. So avoid throwing tea leaves, solid food remains and napkins into the drain. These block the flow of oxygen to the microbes that help in water treatment. Chemicals like paints, medicines, motor oil and solvents kill the microbes that help in water treatment. People need to be made aware of the ill effects of throwing pollutants into the drain.


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Importance of Sanitation

Everyone must know about the adverse effects of poor sanitation.

Effects of poor sanitation Everyone must know about the adverse effects of poor sanitation. The problem is at its worst in villages, where proper sanitation is not available. Villagers defecate in the open, on dry river beds, railway tracks, fields and even directly in water. This causes water and soil pollution. Moreover, it contaminates and affects ground water as well as surface water, resulting in diseases such as cholera, typhoid, polio, meningitis, hepatitis and dysentery. Sanitation is a major problem in developing countries such as India and China. The government is unable to provide proper sanitation through underground drainages. Also, lack of knowledge and of money, illiteracy, large population and lack of social awareness results in improper sanitation. To avoid these problems, low-cost onsite sewage disposal systems should be used. These systems collect human excreta and store it in a hole or a pipe, and later direct it to a sewage treatment plant. In the absence of a proper sanitation network, people can use some other mechanism for sewage disposal. The other mechanisms are septic tanks, chemical toilets, composting pits and vermiprocessing toilets. Septic Tanks Septic tanks are suitable for places such as hospitals, isolated buildings and clusters of houses where there is no sewage. Local governments or private corporations usually provide septic tanks in areas that have no


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direct connection to main sewage pipes. The septic tank system consists of a small sewage treatment system. Chemical Toilets Aeroplanes and trains usually have chemical toilets. A chemical toilet uses chemicals to disinfect human waste and remove its bad odour. That is why trains and aeroplanes do not have elaborate plumbs and sewage. Composting Toilets Another method of clearing human waste is by the process of composting pits. A composting toilet is a system that converts human waste into organic compost and usable soil. This happens when micro-organisms, such as bacteria and fungi, and macro-organisms, such as earthworms, oxidise organic waste to break it down into essential minerals. Vermi-Composting Toilets A vermi-composting toilet is a process that involves earthworms, which treat human excreta. This process is low cost. Moreover, the entire human waste is converted into of vermi-compost. Sulabh Toilets Organisations such as Sulabh International have developed a twin-pit pour flush toilet system that is being used by ten million people every day. The waste from these toilets flows through covered drains into a biogas plant for the generation of biogas and bio-fertilisers. Biogas plants offer safe and hygienic disposal of wastes. Biogas has great advantage, i.e. it is used as a source of low-cost fuel. It can be used for heating, cooking running heat engines, generating mechanical or electrical power. Litter and Waste Litter and waste cause sanitation havoc at public places. This becomes common when exhibitions and fares are conducted.


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Public places such as railway stations, bus depots, airports and hospitals generate a lot of waste, which leads to diseases. To prevent disease, certain measures should be taken and awareness among people should be created.


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Class VII I.I.T.foundation, N.T.S.E.& Science Olympiad Curriculum & Chapter Notes

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