Classification of Organism
Classification of Organism
⇒ There are millions of organisms. It is impossible to study each individual separately. Classification means to categories organism into different groups. Study of an individual of a group gives us the idea of rest of the member of that group.
⇒ Linnaeus divide all organism into two kingdomsPlanate and Animalia in his book “Systema Nature”. The foundation of modern classification system was laid in the line of classification system started by Linnaeus. Therefore Linnaeus is called ‘Father of Taxonomy. Due to disputed position of organism like bacteria, virus, fungi and euglena, there is a need of reconsideration of system of classification.
⇒ The book ‘Genera plantarium’ was written by Benthem and Hooker.
Five Kingdom Classification
⇒ Five Kingdom Classification was proposed in 1969 by R.H. Whittaker. The criteria of classifying organism into five kingdoms are complexity of cell structure, complexity of body of organism, mode of nutrition, life style and phylogenetic relationship.
1. Monera It includes all prokaryotic organism like bacteria.
⇒ Bacterial structure is very simple but they show very complex behaviour.
⇒ They may be photosynthetic chemosynthetic autotrophic. autotrop autotrophic or
⇒ Vast majority of bacteria are heterotrophic.
⇒ Archaebacteria and Eubacteria are the group of bacteria.
⇒ Archaebacteria are found in most harsh condition like hot springs, marshy and extreme salty area.
⇒ Eubacteria is also known as true bacteria.
⇒ Cynobacteria is also known as blue green algae having chlorophyll ‘a’ similar to green plants. They are unicellular, colonial or filamentous found in both fresh water and marine water.
⇒ Nostoc and Anabaena can fix atmospheric nitrogen due to presence of specialised cell heterocysts.
⇒ Chemosynthetic bacteria play a great role in recycling like nitrogen, phosphorous, iron & sulphur.
⇒ Heterotrophic bacteria are decomposer.
⇒ They are helpful for human like making curd, antibiotics, fixing nitrogen, etc.
⇒ Some are pathogen causing disease in human, plant, farm animals and pets.
⇒ Bacteria reproduce mainly by fission.
⇒ The mycoplasma are smallest organism that lack a cell wall. They can survive without oxygen.
⇒ Plasmids are small, circular, double stranded, self replicating extra- chromosomal DNA commonly found in prokaryotes.
2. Protista : All single-celled eukaryotes are placed under protista.
⇒ This group includes diatoms, dinoflagellates, Euglenoids, slime moulds and protozoan.
⇒ Dinoflagellates are mostly marine and photosynthetic.
⇒ Slime moulds are saprophytic protists.
⇒ Protozoan are heterotrophs.
⇒ Protozoan are grouped as amoeboid protozoans (Amoeba), flagellated protozoans (Trypanosoma) ciliated protozoans (Paramoecium), sporozoans (Plasmodium).
⇒ Euglena have both heterotrophic and autotrophic nutrition.
⇒ Euglena is a connecting link between plants and animals.
3. Fungi: This kingdom includes nongreen plants having heterotrophic nutrition.
⇒ Most fungi are saprophytes obtaining their nutrition from dead and decaying organic matter. Ex. Mushroom, Toadstools.
⇒ Yeasts are unicellular fungi used in making bread and beer. They reproduce asexualy by budding.
⇒ Some fungi are parasitic causing disease in plants and animals.
⇒ Aspergillus, Mucor, Rhizopus etc are the example of fungi.
⇒ Except yeasts fungi are filamentous consist of long slender thread like structure called hyphae.
⇒ Some fungi live as symbionts in association with algae known as lichensand with the root of higher plant called mycorrhiza.
⇒ Some fungi are source of antibiotic like Penicillum.
4. Plantae: This kingdom includes all plant except algae, diatoms, fungi and member of monera and protista.
5. Animalia: Almost all animal comes under this kingdom except protozoan.
⇒ Binomial nomenclature: There was the need of uniform international naming of organism. In biology every organism is represented by two proper name. The first name is genus, always started with capital letter and the second name is species started with small letter. For example scientific name of human is Homo sapiens. Homo is the name of genus, whose one species is sapiens.
⇒ Panchanan Maheswari popularised the use of embryological characters in taxonomy.
⇒ The botanist Joseph Dalton Hooker is credited with creating one of the first widely used natural system of plant classification.
⇒ Basic unit of classification is species.
⇒ Highest unit of classification is kingdom.
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