Biological Classification

 

Biological Classification

Biological classification is the scientific procedure of arranging organisms into groups and groups on the base of their parallels and distinctness and placing the group in a scale of orders.

v Significance of classification-

 • It isn't 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.

 • The organism of history can not be studied without a proper system of classification.

 Classification

 • Artificial system of classification

 • Natural system of classification

 • Phylogenetic system of classification

1.    Artificial system of classification – Only one or two morphological characters for grouping of organism is used. Flowering andnon-flowering Plants, enaima and anaima. Aristotle classification.

2.    Natural system of classification – Takes into consideration similar study of a number of characters so as to bring out natural parallels and distinctness and hence natural connections among the organisms. Bentham and Hooker classification,etc.

3.    Phylogenetic System of Classification – Grounded on the evolutionary relationship of organisms. In this system organism are classified on the base of their elaboration on earth from primitive to largely evolved. Engler and Prantl classification and Hutchinson classification,etc.

 Depending upon the type of system of classification organism are classified into following Kingdom system.

 Biological Classification

Kingdom system of classification

 • Two Kingdom: Plantae Animalia

 • Three Kingdom: Plantae Protista Animalia

 • Five Kingdom: Monera Protista Fungi Plantae Animaila

 • In two kingdom system of classification organisms are grouped on the base of presence and absence of cell wall as proposed by Linnaeus ( father of taxonomy).

 • Three Kingdom systems-Haeckel separated unicellular creatures, algae and fungi on the base of lack of towel isolation 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.

a)    Monera

The Kingdom includes all prokaryotes-mycoplasma, bacteria, actinomycetes and cyanobacteria.

 1. Unicellular, prokaryotes and contain the most primitive of living forms

.2. The cells are bitsy and cell wall is generally present.

 3. Inheritable accoutrements aren't organized into nexus and contain naked DNA.

 4. Membrane bounded organelles are absent.

 5. Reproduction is asexual except gene recombination.

 6. 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.

Biological Classification

 They're group of utmost primitive prokaryotes which live under utmost hostile conditions like minimum salty Kingdom (halophiles), hot springs (thermoacidophiles) and marshy Kingdom (methanogens). They differ from other bacteria in having different cell wall structure ( absence of peptidoglycan).

Methanogens are present in the gut of several ruminant creatures like cows and buffalo, which is responsible for product of biogas (methane) from soil of these creatures.

·       Eubacteria – They're 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, social or filamentous, fresh water, marine or terrestrial. Some of them have specialized heterocyst cells to perform nitrogen obsession (Nostoc and Anabaena).

 Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammoniaetc. to produce energy and help in recycling of nitrogen, phosphorous, sulphuretc. Heterotrophic bacteria are most abundant and act as decomposer. They're helpful in product of curd, antibiotic and fixing nitrogen in leguminous Plants. Some of them are pathogenic and beget complaint like cholera, typhoid, tetanus and citrus canker.

 

 Mycoplasma – they're the simplest free living prokaryotes. They're also known as PPLO (Pleuropneumonia like organism). They warrant cell wall and can survive without oxygen. They beget complaint in Plants and creatures.

Biological Classification

b)    Protista

Kingdom Protista includes Chrysophytes, Dinoflagellates, Eugleoids, slime mould and Protozoans.

 

v Chrysophytes

1. It includes all unicellular and social eukaryotes.

 2. Utmost of them are submarine forming plankton.

 3. Mode of nutrition may be photosynthetic, saprophytic, parasitic or holozoic.

 4. Flagella if present are 11 stranded with 9 2 arrangement of microtubules composed of tubulin.

 5. Inheritable material consists of 2 or further DNA motes.

Biological Classification

v Dianoflagellates

 • They includes diatoms and golden algae (desmids) plant in fresh water as well as marine water.

 • In diatoms cell wall forms two thin lapping cells which fit together as in cleaner box.

 • The siliceous imperishable cell wall pile over at the bottom of water budgets and form big stacks called diatomaceous earth. It may extend for hundred cadence and used for polishing, filtration of canvas and bathos. They're principal patron in abysses.

 • They're principally unicellular, motile, biflagellate and photosynthetic protists.

 • Predominate colour is golden brown but unheroic, green, red and indeed blue also exists.

 • Some Dinoflagellates like Gymnodinium and Gonyaulax grow in large number in the ocean and make the water look red and beget the so called “ red drift”.

v Euglenoids

 • They're Euglena like unicellular flagellates which retain pellicle rather of cell wall which make their body flexible.

 • They've two flagella, one short and other long.

 • They're photosynthetic in presence of sun and act as bloodsuckers in absence of sun.

 • Illustration-Euglena, Peranema.

v Slime Moulds

 • They're saprophytic protists and feeds on decaying outgrowths and leaves.

 • Under favorable condition, they form an aggregation called plasmodium which produce regenerating bodies bearing spores.

 • The cell wall of spores contain cellulose.

 • The spores are dispersed by air currents.

 • Illustration-Physarum, Fuligo.

v Protozoans

 • All protozoans are heterotrophs and live as bloodsuckers or spongers.

 • They're considered as primitive cousins of creatures.

 • Amoeboids move and capture food by pseudopodia. Some are parasitic also.

 • Flagellated protozoans are free-living or parasitic. They've flagella.

 • Ciliated protozoans are submarine and have cilia each over the body for movement.

 • Sporozoans includes organism that have contagious spore like stage in their life cycle.

 Biological Classification

c)  Kingdom Fungi –

• They're achlorophyllous, heterotrophic, spore forming,non-vesicular eukaryotic organisms.

 • Cell wall is made up of chitin or fungal cellulose.

 • 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 reduplication by oospores, ascospore and basidiospores.

 • Sexual cycles involves the following way-

 1. Plasmogamy, emulsion of manly and womanish gametes.

 2. Karyogamy, emulsion of two capitals.

 3. Meiosis in zygote to produce haploid spores.

 Phycomycetes –

 • They're plant in submarine niche and on decaying wood in wettish and damp places.

 • The mycelium is aseptate and coenocytic.

 • Asexual reduplication by zoospores (motile) or aplanospores (non-motile).

 • Illustration-Mucus, Rhizopus, Albugoetc.

 

 Ascomycetes (The sac fungi)

 • They're saprophytic, decomposers, parasitic or coprophilous ( growing on soil).

 • Mycelium and fanned and septate and asexual spores are conidia.

 • Sexual spores are called ascospores produced inside the fruiting body called ascocarps.

 Illustration-Neurospora, Asperigillus, Clavicepsetc.

 Basidiomycetes (The club fungi)

 • The mycelium is fanned and septate.

 • Vegetative reduplication is by fragmentation. Asexual spores aren't plant. Sexual reduplication is by two vegetative or physical cells forming basidium.

 • Basidiospores are produced in basidium by developing a fruiting body called basidiocarps.

 • Illustration-Agaricus, Ustilago, Puccinia.

 Deuteromycetes (The fungi amiss)

 • Only vegetative and asexual phase is known.

 • Mycelium is septate and fanned. Some members are saprophytes or parsites.

 • Illustration-Alternaria, Trichoderma, Colletotrichu.

d)  Kingdom Plantae

 1. Eukaryotic, chlorophyll bearing organism.

 2. Life cycle is divided into diploid saprophytic and haploid gametophytic, which alternate with each other.

 3. Kingdom Plantae includes Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.

e)  Kingdom Animalia

 1. Heterotrophic, eukaryotic organisms that are multicellular and cell wall is absent in the cell.

 2. Mode of nutrition is holozoic and reserve food is glycogen or fats.

 3. Sexual reduplication is by coition between manly and womanish followed by embryological development.

 Virus, Viroids and Lichens

. Five Kingdom system of classification don't includes Virus, Viroids and Lichens.

Virus

Contagions are non-cellular organisms having inert crystalline structure outside the living. When they enter the living cell, they take over the ministry of living cell to replicate themselves.

 •D.J.Ivanowsky honored certain microbes as unproductive organism of mosaic complaint of tobacco.

 • In addition to proteins, contagions also contain inheritable material that could be DNA or RNA. In general, contagion that infect Plants have single stranded RNA and contagion that infect creatures have double stranded DNA.

 • Some common conditions caused by contagion are common deep freeze, influenza, AIDS, small spell, splint rolling and curling.

 • Bacteria feeding contagion are calledBacteriophage.They're generally double stranded DNA contagions.

 • The protein fleece called capsid is made of small subunits called capsomeres, protects the nucleic acid. These capsomeres are arranged in spiral or polyhedral geometric forms.

·       Viroids

 Viroids are discovered byT.O.Diener as new contagious agent lower than contagion causing potato spindle tuber complaint. They're free RNA without protein fleece.

·       Lichens

Lichens are symbiotic association between algae and fungi. The algal part is called Phycobiont and fungal corridor are called Mycobiont. They're good pollution index as they don't grow in weakened Kingdom.