Classification 28 March 2013
08:09
Classification of Organism: Classification helps us in exploring the diversity of life forms. The classification of life forms is related to their evolution. The major characteristics considered considered for classifying all organisms into five major kingdoms are: are: ○ whether they are made of prokaryotic or eukaryotic cells ○ whether the cells are living singly or organised into multi-cellular and thus complex organisms ○ whether the cells have a cell-wall and whether they prepare their own food. All living organisms are divided divided on the above bases into five kingdoms, namely Monera, Protista, Fungi, Plantae and Animalia. Animalia .
NOTE: Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) have tried to classify all living organisms into broad categories, called kingdoms. The classification Whittaker proposed has five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, and is widely used. These groups are formed on the basis of their cell structure, mode and sourc e of nutrition and body organisation. The modification Woese introduced by dividing the Monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria) is also in use. Further classification is done by naming the sub-groups at various levels as given in the following scheme:
Broadly, a species includes all organisms that are similar enough to breed and perpetuate.
Kingdom Monera =============== ○ These organisms do not have a defined nucleus or organelles, nor do any of them show multi-cellular body designs. On the other hand, they show diversity based on many other characteristics. Some of them have cell walls while some do not. This group includes bacteria, blue-green algae or cyanobacteria, and mycoplasma. mycoplasma . Bacteria: Bacteria are grouped under four categories based on their shape: the spherical Coccus (pl.: cocci), the rod-shaped Bacillus (pl.: bacilli), the comma-shaped Vibrium (pl.: vibrio) and the spiral Spirillum (pl.: spirilla)
Nutrition: The four nutritional categories found in bacteria are : Autotrophs
synthesize their own organic food.
Saprotrophs feed on dead and decaying matter. Symbionts
use food from other living organisms with which they are associated for mutual benefit.
Parasites
absorb food from living organisms and cause harm to them
Respiration Respiration in bacteria may be either Aerobic
using oxygen for respiration or
Anaerobic respiration in the absence of oxygen. Cellular respiration or breakdown of food to release energy occurs in mesosomes which are the inner extensions of the cell membrane. Reproduction Asexual Reproduction
Bacteria reproduce asexually asexually by binary fission under favorable conditions conditions it takes about 20 minutes for one bacteria to divide into two by binary fission.
Sexual Reproduction
Some bacteria show a primitive mode of sexual reproduction. It is different from sexual reproduction in higher form. The steps are: ○ Two conjugating (lie very close for exchange of genes) bacteria are held together by pili. ○ A segment of DNA strand is transferred from one bacterium to another bacterium.
Many species of bacteria possess rings of DNA called plasmids, apart from the chromosome , which replicate along with bacterial chromosome and bear genes for antibiotic resistance, sex factor etc.
Beneficial and harmful bacteria They harm us by causing many diseases. On the other hand some bacteria are very useful. Diseases Caused By Bacteria Name of Bacterium
Human Disease Symptoms Cure
1. Vibrio cholerae
Cholera
2. Salmonella typhi
Typhoid
3. Clostridium tetani
Tetanus
4. Coryneb Corynebact acteri erium um dipther diptheriae iae Diphth Diphtheri eria a 5. Mycobact Mycobacterium erium tuberculosi tuberculosiss Tuberculosi Tuberculosiss
Name Name of Bacte Bacteriu rium m
Plant Plant Diseas Diseases es Sympto Symptoms ms Cure Cure
Xanthomonas axonopodis axonopodis Citrus canker
Beneficial Activities of Bacteria Name of bacterium
Activities
1. Rhizobium
Found in roots of legumes, (Peas, grams, Pulses etc) fixes atmospheric nitrogen as ammonia, which is then converted into useful amino acid.
2. Azot Azotob obac acte terr
Make Makess the the soi soill fer ferti tile le.. It fixe fixess atm atmos osph pher eric ic nitr nitrog ogen en in in the the soi soil. l.
3. Streptomycetes
Produces Streptomycin antibiotic. [Used to treat Tuberculosis]
4. Lactobacillus
Ferments lactose (milk sugar) to lactic acid. This helps in setting of milk into curd.
5. Methanogenic bacteria
Sewage treatment; Production of Methane gas (biogas) from the dung of ruminant animals.
Cyanobacteria These were earlier called the blue green algae. algae . A very successful group on primitive earth. They could carry out photosynthesis and the oxygen releases during the process changed the earth’s atmosphere and gradually the level of oxygen increased in the earth’s atmosphere. Mycoplasmas These are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants. Archaebacteria Kingdom Monera includes two groups 1. Archaebacteria and 2. Eubacteria Archaebacteria includes bacteria that live in unusual environments particularly at low levels of oxygen. Main types of Archaebacteria are ○ Methanogenic bacteria that live in sewage and intestinal tracts tracts of animals. Methanogens are present in the guts of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals. ○ Thermo acidophilic bacteria that live in hot springs. ○ Halophilic bacteria live in salty conditions conditions e.g. where hot sun concentrates sea water Eubacteria: include cyanobacteria and all other bacteria.
KINGDOM PROTISTA ================== ○ unicellular eukaryotic ○ Some of these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around. ○ Their mode of nutrition can be autotrophic or heterotrophic. Examples are unicellular algae, diatoms and protozoans. Protista: Protista: unicellular algae, diatoms and protozoans (Amoeba, paramecium, Euglena). 3 Categories: a. Animal-like Protists. b. Plant-like Protists. c. Fungus-like Protists. I. Animal-like Protists: e.g. Protozoan means "First Animal" 4 Groups of Animal-like Protists 1. Sarcodines: e.g. amoeba 2. Ciliates : e.g. Paramecium
3. Flagellates: 4. Sporozoans : e.g. Plasmodium 1. Sarcodines: ○ Have pseudo pods (Greek:“false foot”) ○ Many have shells. These shells form limestone, marble and chalk. Amoeba: ○ Contractile Vacuoles: controls amount of water inside ○ Food Vacuole: Vacuole: where food is digested. ○ They are sensitive to light and some chemicals. ○ Reproduces by binary fission
Entamoeba ○ One common species is Entamoeba histolytica which causes amoebic dysentery in humans. ○ It is amoeboid in form. ○ New host gets infected when the cyst is swallowed along with contaminated food or water. The cyst bursts and releases Entamoeba in the intestines where it causes local abscesses (open injury). ○ The symptoms of amoebic dyscenteiy are abdominal pain, nausea, blood and mucus with stool. 2. Ciliates ○ Tiny hair-like projections used for movement, to gather food and as feelers. Paramecium ○ Pellicle Pellicle:: tough outer wall. ○ Slipper shaped ○ Oral groove: like the mouth ○ Gullet: holds food. ○ Food Vacuole: digests food. ○ Anal Pore: removes wastes ○ 2 Contractile Vacuoles ○ 2 Nuclei ○ Reproduces by either binary fission or conjugation conjugation..
3. Flagellates (Zooflagellates) ○ Have a Flagellum Flagellum:: a long whip-like structure used for movement. ○ Many live in animals ○ Symbiosis a close relationship, at least one benefits. ○ Mutualism Mutualism:: when both partners benefit. The Trypanosome Causative agent of African Sleeping Sickness. Sickness. Transmitted from infected wild animals by the tsetse fly to humans Victim develops a fever and becomes weak and anemic. This is due to the effect of the toxic metabolites produced by this organism. Finally the parasites invade the fluid surrounding the brain and spinal cord, the person loses consciousness and dies. Drugs are effective in the early stages of this disease.
4. Sporozoans ○ All Sporozans are parasites. ○ They feed on cells and body fluids. ○ Form from Spores (tiny reproductive cells). ○ Pass from one host to another. ○ Pass from ticks, mosquitoes or other animals to humans. Plasmodium vivax:
An excellent example of a sporozoan is Plasmodium vivax , the causative agent of malaria. malaria . There are two stages involved in the life cycle of Plasmodium vivax ; Asexual (in the human) and Sexual (in the mosquito). mosquito). Sexual phase is spent in the female Anopheles mosquito □ When an infected mosquito bites a human, spores enter the bloodstream and produce gametes in the red blood cells. □ When an infected human is bitten by a mosquito, gametes unite in the gut of the mosquito to form a zygote. □ In the mosquito, the zygote matures into more spores which are passed on to the next human victim.
Male Anopheles cannot cause malaria as it feeds on plant juices and not human blood. II. Plant-like Protists (Algae) ○ Unicellular and Multicellular ○ Colonies (groups of unicellular protists) ○ Can move on their own ○ Autotrophs Autotrophs:: make their own food from simple materials using light energy (photosynthesis).
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70% of the Earth’s oxygen is produced by Plant-like Protists! Pigments:: chemicals that produce color Pigments
6 Groups of Plant like Protists ○ Euglenoids ○ Diatoms ○ Dinoflagellates ○ Red Algae ○ Green Algae ○ Brown Algae Euglenoids ○ Green ○ Unicellular ○ Live in fresh water ○ Autotrophs, but can be heterotrophs under certain conditions. ○ Flagella ○ Eyespot: sensitive to light. ○ Chloroplasts ○ Pellicle Diatoms ○ Unicellular ○ 10,000 living species. ○ Aquatic ○ Glass like cell wall ○ Thousands of species of diatoms form food for aquatic animals. ○ Diatoms are either unicellular, unicellular, colonial or filamentous and occur in a wide variety variety of shapes ○ Each cell has a single prominent nucleus and plastids. They produce shells (cell walls) walls) containing silica. ○ diatoms have left behind large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’. earth’. Being gritty this soil is used in polishing, filtration of oils and syrups. Diatoms are the chief ‘producers’ in the oceans. ○ Diatomaceous earth: earth: coarse powder that comes from dead diatoms (toothpaste, car polish & reflective paint). Dinoflagellates ○ Unicellular ○ Cell walls are like plates of armor. ○ Two flagella ○ Spins when it moves. ○ Colorful (pigments) ○ Can glow in the dark. ○ Causes Red Tide ○ Very often, red dianoflagellates (Example: Gonyaulax) undergo such rapid multiplication that they make the sea appear red (red tides). Toxins released by such large numbers may even kill other marine animals such as fishes. Red Tide From time to time, there are algal blooms and the so-called red tides form. Toxins from the dinoflagellates are released. Fish die from the toxin and paralytic shellfish poisoning(PSP) may occur.
Red Algae ○ Multicellular seaweeds ○ Live in deep ocean waters ○ Used for ice cream and hair conditioner Used as food in Asia
Colour of the Red Sea is due to the dominant occurrence of a red alga. Green Algae ○ Most are unicellular ○ Some form colonies ○ Few are multicellular ○ Can live in fresh and salt water and on land in damp places. ○ Very closely related to green plants. Brown Algae ○ Commonly called seaweed ○ Can contain brown, green, yellow, orange and black pigments. ○ Attach to rocks ○ Have air bladders ○ Giant Kelp can be 100 meters long! ○ Used as food thickeners Usefulness of Algae: ○ Provide food food for fish as as part of phytoplankton (organisms floating floating on the water surface) ○ These are rich sources of vitamins A and E. ○ Many marine forms are important sources sources of iodine, potassium and other minerals. ○ Blue-green algae increase the soil fertility by fixing atmospheric nitrogen. ○ Some algae can fix atmospheric nitrogen, nitrogen, so they are a source of natural fertilizer for the plants. ○ A group of algae ( diatoms) deposit silica in their walls. After their death these these algae are preserved as fossils. Their deposits in large amounts are used as filters, and for lining of furnaces.
III. Fungus-like Protists ○ Heterotrophs ○ Have cell walls. ○ Many have flagella and are able to move at some point in their lives. ○ Three types : Slime Molds, Water & Downy Molds ○ Reproduce with Spores (tiny cell that is able to grow into a new organism) Water & Downy Molds ○ Live in water or moist places. ○ Tiny threads that look like fuzz. ○ Attack food crops ○ Caused the Irish Potato Famine. Slime Molds: ○ Reproduce by Fruiting Bodies: ○ The Fruiting Bodies contain Spores. ○ At first they look like ameba, then later they look like mold. ○ Live on moist shady places. ○ Feed on bacteria and other microorganisms.
KINGDOM FUNGI: =============== ○ These are heterotrophic eukaryotic organisms. ○ They use decaying organic material as food and are therefore called saprophytes. ○ Many of them have the capacity to become multicellular organisms at certain stages in their lives. ○ They have cell-walls made of a tough complex sugar called chitin. Some fungal species live in permanent mutually dependent relationships with bluegreen algae (or cyanobacteria). Such
relationships are called symbiotic. symbiotic. These symbiobic life forms are called lichens. lichens. Examples: Examples: yeast, mushrooms, Penicillium, Agaricus, Aspergillus
Four main kinds of Fungi The fungi are of four main kinds 1. Yeasts, Yeasts , which are unicellular. moulds, which have irregular shape. 2. Slime moulds, 3. Mushrooms and toadstools, toadstools, which are large enough to be seen by naked eyes. 4. Lichens and mycorrhizae which exist in symbiotic associations. Yeast: Nutrition Yeast is saprotrophic. saprotrophic. It can directly absorb simple sugar (glucose) (glucose) but for obtaining sucrose sucrose (cane sugar) it gives out the enzyme zymase which breaks down sucrose into simple sugars. The simple sugars are then simply absorbed into the cell Slime Moulds These consist of a naked, creeping multinucleate mass of protoplasm sometimes covering up to several square metres. Mushrooms and Toadstools The vegetative part of the mycelium lies concealed in the substratum (in ground or in wood, etc.) When conditions are favorable the umbrella like mushroom grow out with a stalk and a cap. Lichens : Lichens are symbiotic associations associations i.e. mutually useful associations, between green algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients nutrients and water for its partner. So close close is their association that if one saw a lichen in nature one would never imagine imagine that they had two different organisms within within them. ○ Lichens are very good pollution indicators – they do not grow in polluted areas. Economic importance of Fungi Harmful Fungi: Rust): It causes brown patches on leaf and stem of wheat. It decreases the yield of wheat and 1. Puccinia graminis (Wheat Rust): makes it unfit for human consumption. 2. Rhizopus or (Bread Mould) grows on bread. If the bread is ex posed to warm and humid conditions a cottony mass develops in few days. This white cotton mass later develops a greyish black colour. i. The whitish network is called mycelium. ii. The mycelium contains thread like structures called hyphae. iii. The root-like sturctures growing growing out of the hyphae penetrate the bread, and secrete digestive enzymes (extracellular digestion) and absorb the digested food. 3. In human, skin diseases like ringworm and athlete’s foot are caused by fungi. fungi. Some ear infections are also caused by fungi.
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Certain Mushrooms (such as Agaricus campestris) are edible. Yeasts is used for fermentation during manufacture of bread, beer, soya sauce, cheese and wine. getting minerals from the environment environment while fungi Mycorrhizae are fungi associated associated with roots of plants. Roots benefit in getting gets food from the plant in return through such association. Neurospora has been a favourite experimental material in Genetics. Various antibiotics are derived from fungi. Penicillin is obtained from Peni Penicilliu cillium m notat notatum um. Its antibiotic effect was discovered by chance by Alexander Flemming in 1927.
KINGDOM PLANTAE: ================= Plants are divided into five groups: Thallophytes, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
The first level of classification among plants depends on whether the plant body has well differentiated, distinct components. The next level of classification is based on whether the differentiated plant body has special tissues for the transport of water and other substances within it. Further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.
Thallophytes: ○ commonly called algae, predominantly aquatic. ○ Examples are Spirogyra, Ulothrix, Cladophora and Chara Bryophytes: ○ amphibians of the plant Kingdom ○ Example: Moss (Funaria) and Marchantia. Pteridophytes: ○ Examples: Marsilea, ferns and horse-tails.
The thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores. The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore called ‘cryptogamae’, or ‘those with hidden
reproductive organs’.
On the other hand, plants with well differentiated reproductive tissues that ultimately make seeds are called phanerogams. phanerogams. Seeds are the result of the reproductive process. process. They consist of the embryo along with stored stored food, which serves for the initial growth of the embryo during germination. germination. Gymnosperms: Examples are pines, such as Deodar, Cycas Angiosperms: Plant embryos in seeds have structures called cotyledons. cotyledons. Cotyledons are called ‘seed ‘ seed leaves’ leaves ’ because in many instances they emerge and become green when the seed germinates. Thus, cotyledons represent a bit of pre -designed plant in the seed. The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed. Plants with seeds havin g a single cotyledon are called monocotyledonous or monocots. monocots. Plants with seeds having two cotyledons are called dicots. dicots. Examples: Monocots – Paphiopedilum, Dicots – Ipomoea KINGDON ANIMALIA: ================== They are further classified based on the extent and type of the body design differentiation found. Animals are divided into ten groups: Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Mollusca, Echinodermata, Protochordata and Vertebrata.
Porifera: Porifera: commonly called sponges, sponges, and are mainly found in marine habitats. E.g. Euplectelia, Sycon, Spongilla
Coelenterata : The body is made of two layers of cells. cells . Some of these species live in colonies (corals), while others have a solitary like –span (Hydra). Jellyfish and sea sea anemones are common common examples
Platyhelminthes: The body is bilaterally symmetrical, meaning that the left and the right halves of the body have the same design. There are three layers of cells from which differentiated tissues can be made, which is why such animals are called triploblastic. triploblastic. However, there is no true internal body cavity or coelom, coelom , in which well developed organs can be accommodated. The body is flattened flattened dorsi ventrally, meaning from top to bottom, bottom, which is why these animals are called called flatworms. They are either freeliving or parasitic. Some examples are freeliving animals like planarians, or parasitic animals like liverflukes
Nematoda: The nematode body is also bilaterally symmetrical and triploblastic. However, the body is cylindrical rather than flattened. flattened. There are tissues, but no real organs, although a sort of body cavity or a pseudocoelom, pseudocoelom, is present. T hese are very familiar as parasitic worms causing diseases, such as the worms causing elephantiasis (filarial worms) worms ) or the worms in the intestines (roundworm or pinworms).
Annelida: Annelid animals are also bilaterally symmetrical and triploblastic, but in addition they have a true body cavity. cavity. This allows true organs to be packaged in the body structure.
Arthropoda: This is probably the largest group of animals. animals. These animals are bilaterally symmetrical and segmented. There is an open circulatory system, and so the blood does not flow in welldefined blood vessels. The coelomic cavity is blood-filled. They have jointed legs (the word ‘arthropod’ means ‘jointed legs’). Some familiar familiar examples are prawns, butterflies, houseflies, spiders, spiders, scorpions and crabs.
Mollusca: In the animals of this group, there is bilateral symmetry. symmetry. The coelomic cavity is reduced. There is little segmentation. They have an open circulatory system and kidney-like organs for excretion. There is a foot that is used for moving around. E xamples are nails and mussels.
Echinodermata: In Greek, echinos means hedgehog, and derma means skin. Thus, these are spiny skinned organisms. These are exclusively freeliving marine animals. They are triploblastic and have a coelomic cavity. They also have a peculiar water-driven tube system that hey use for moving around. They have hard calcium carbonate structures structures that they use as a skeleton. Examples are starfish and sea urchins
Protochordata: they show a new feature of body design, namely a notochord, at least at some stages during their lives. Examples are Balanoglossus, Herdemania and Amphioxus Vertebrata: Vertebrates are bilaterally symmetrical, triploblastic, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs. All chordates possess the following features: (i) have a notochord (ii) have a dorsal nerve cord (iii) are triploblastic (iv) have paired gill pouches (v) are coelomate. They are further divided into Pisces, Amphibia, Reptilia, Aves, Mammalia.
========================================================================================================= Viruses & Viroids: =============== Viruses did not find a place in classification since they are not truly ‘living’, if we understand living as those organisms that have a cell structure. The viruses are non-cellular organisms that are characterised by having an inert crystalline structure outside the living cell. The name virus that means venom or poisonous fluid was given by Pasteur. D.J. Ivanowsky (1892) recognised certain microbes as causal organism of the mosaic disease of tobacco. tobacco . These were found to be smaller than bacteria because they passed through
bacteria-proof filters. M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium vivum fluidum (infectious living fluid). W.M. Stanley (1935) showed that viruses could be crystallised and crystals consist largely of proteins. They are inert outside their specific host cell. Viruses are obligate parasites. In addition to proteins viruses also contain genetic material, that could be either RNA or DNA. DNA. No virus contains both RNA and DNA. DNA. A virus is a nu cleoprotein and the genetic material is infectious. ○ In general, viruses that infect plants have single stranded RNA ○ viruses that infect animals have either single or double stranded RNA or double stranded stranded DNA. ○ Bacterial viruses viruses or bacteriophages (viruses that infect the bacteria) are usually double stranded DNA viruses. viruses. The protein coat called capsid capsid made of small subunits called capsomeres, capsomeres, protects the nucleic acid. These capsomeres capsomeres are arranged in helical or polyhedral geometric geometric forms. Viruses cause diseases like mumps, small pox, herpes and influenza. influenza . AIDS in humans is also caused by a virus. In plants, the symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth. Viroids : In 1971 T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. disease. It was found to be a free RNA; RNA ; it lacked the protein coat that is found in viruses, hence the name viroid. The RNA of the viroid was of low molecular weight.
Nomenclature: The system of scientific naming or nomenclature we use today was introduced by Carolus Linnaeus ○ The binomial nomenclature makes for a uniform uniform way of identification of the vast diversity diversity of life around us. ○ The binomial nomenclature is made up of two words – a generic name and a specific name. ○ We limit ourselves to writing the name of the genus and species of that particular organism.
