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Biological Classification Notes Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the group in a hierarchy of categories. Importance of classification- « Itis not possible to study every organism. Study of one or two organism of a group gives sufficient information about the essential features of the group. « It helps in identification of new organism. « Classification helps in knowing the relationship amongst different groups of organisms. e« The organism of past cannot be studied without a proper system of classification. Classification e Artificial system of classification « Natural system of classification e Phylogenetic system of classification Artificial system of classification— Only one or two morphological characters for grouping of organism is used. Flowering and non-flowering plants, enaima and anaima. Aristotle classification. Natural system of classification— Takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms. Bentham and Hooker classification, etc. Phylogenetic System of Classification— Based on the evolutionary relationship of organisms. In this system organism are classified on the basis of their evolution on earth from primitive to highly evolved. Engler and Prantl classification and Hutchinson classification, etc. Depending upon the type of system of classification organism are classified into following kingdom system. Kingdom system of classification « Two kingdom : Plantae Animalia « Three kingdom : Plantae Protista Animalia « Five kingdom : Monera Protista Fungi Plantae Animaila « Intwo kingdom system of classification organisms are grouped on the basis of presence and absence of cell wall as proposed by Linnaeus( father of taxonomy). « Three kingdom systems- Haeckel separated unicellular animals, algae and fungi on the basis of lack of tissue differentiation and new kingdom Protista was introduced. « Five kingdom systems- R.H.Whittaker divided all the organism into five kingdom in order to develop phylogenetic classification. 1. Monera— The kingdom includes all prokaryotes- mycoplasma, bacteria, actinomycetes and cyanobacteria. Unicellular, prokaryotes and contain the most primitive of living forms The cells are microscopic and cell wall is generally present. Genetic materials are not organized into nucleus and contain naked DNA. Membrane bounded organelles are absent. Reproduction is asexual except gene recombination. aa Fon = Flagella may be present and are of single stranded. Example- Blue-green algae, Bacteria, etc. Bacteria are the most abundant micro-organism that can survive in all kinds of climate. rai Bacilli Spirilla Vibrio « They are group of most primitive prokaryotes which live under most hostile conditions like extreme salty area (halophiles), hot springs (thermoacidophiles) and marshy area (methanogens). They differ from other bacteria in having different cell wall structure (absence of peptidoglycan). Methanogens are present in the gut of several ruminant animals like cows and buffalo, which is responsible for production of biogas (methane) from dung of these animals. Eubacteria — They are called as true bacteria. They contain rigid cell wall, if motile contain flagellum. Cyanobacteria or blue-green algae are gram positive photosynthetic bacteria. They contain chlorophyll a and carotenoids. They may be unicellular, colonial or filamentous, fresh water, marine or terrestrial. Some of them have specialized heterocyst cells to perform nitrogen fixation (Nostoc and Anabaena). Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammonia etc. to produce energy and help in recycling of nitrogen, phosphorous, sulphur etc. Heterotrophic bacteria are most abundant and act as decomposer. They are helpful in production of curd, antibiotic and fixing nitrogen in leguminous plants. Some of e They have two flagella, one short and other long. e They are photosynthetic in presence of sunlight and act as predators in absence of sunlight. e Example- Euglena, Peranerma. Slime Moulds e They are saprophytic protists and feeds on decaying twigs and leaves. e Under favorable condition, they form an aggregation called plasmodium which produce fruiting bodies bearing spores. e Thecell wall of spores contain cellulose, ¢ The spores are dispersed by air currents. e Example- Physarum, Fuligo. Protozoans e All protozoans are heterotrophs and live as predators or parasites. e They are considered as primitive relatives of animals. e Amoeboids move and capture food by pseudopodia. Some are parasitic also. ¢ Flagellated protozoans are free-living or parasitic. They have flagella. ¢ Ciliated protozoans are aquatic and have cilia all over the body for movement. e Sporozoans includes organism that have infectious spore like stage in their life cycle. Amoeboids porozoans Plasmodium Flagellated Kingdom Fungi- e They are achlorophyllous, heterotrophic, spore forming, non-vesicular eukaryotic organisms. e Cell wall is made up of chitin or fungal cellulose. e« Reserved food is glycogen. Mode of nutrition is saprophytic, parasitic or symbiotic. Reproduction may be vegetative (fragmentation, fission or budding), asexual (conidia, sporangiospores or zoospores) or sexual reproduction by oospores, ascospore and basidiospores. Sexual cycles invalves the following steps- . Plasmogamy, fusion of male and female gametes. . Karyogamy, fusion of two nuclei. . Meiosis in zygote to produce haploid spores. Phycomycetes— They are found tn aquatic habitat and on decaying wood in moist and damp places. The mycelium is aseptate and coenocytic. Asexual reproduction by zoospores( motile) or aplanospores (non-motile). Example- Mucus, Rhizopus, Albugo etc. Ascomycetes (The sac fung}) They are saprophytic, decomposers, parasitic or coprophilous (growing on dung). Mycelium and branched and septate and asexual spores are conidia. Sexual spores are called ascospores produced inside the fruiting body called ascocarps. Example- Neurospora, Asperigillus, Claviceps etc. Basidiomycetes (The club fungi) The mycelium is branched and septate. Vegetative reproduction is by fragmentation. Asexual spores are not found. Sexual reproduction is by two vegetative or somatic cells forming basidium. Basidiospores are produced in basidium by developing a fruiting body called basidiocarps. Lichens are symbiotic association between algae and fungi. The algal part is called Phycobiont and fungal parts are called Mycobiont. They are good pollution indicator as they do not grow in polluted area. 
