SYSTEMS OF CLASSIFICATION :
- Earliest Classification was given by Aristotle. Divided plants into herbs, shrubs and trees. Animals into those with RBC’s and those who do not have it.
Two kingdom classification :
- Given by Carolous Linnaeus − Plant kingdom and Animal kingdom.
Five kingdom classification :
- By R. H. Whittaker. Monera, Protista, Fungi, Plantae and Animalia are the five kingdoms.
Kingdom Monera :
Bacteria :
- Have bacteria a sole member.
- Bacteria can have shapes like: Coccus (spherical), Bacillus (rod-shaped), Vibrio comma shaped) and sprillum (spiral shaped).
- Bacteria found almost everywhere and can be Photosynthetic autotrophs, Chemosynthetic autotrophs or Heterotrophs.
Archaebacteria :
- Differs from bacteria having different cell wall structure.
- They live in most harsh habitats
- Halophiles (salt-loving)
- Thermophiles (in hot springs)
- Acidophiles (high acidic condition)
- Methanogen (marshy area)
- Methanogen are also found in the gut of ruminant and produces biogas.
Eubacteria :
- Called true bacteria having a rigid cell wall, and if motile a flagellum.
- They also known as blue green algae or Cyanobacteria.
- Cyanobacteria are photosynthetic autotrophs.
- Unicellular, colonial or filamentous, marine and terrestrial algae.
- Colonies are surrounded by gelatinous sheath.
- Some of these can fix atmospheric nitrogen by specialized cells called heterocyst, e.g. Nostoc and Anabaena.
- Chemosynthetic autotrophs: Oxidize various inorganic substances like nitrates/nitrites, ammonia and use released energy for their ATP production.
- Heterotrophic bacteria:
- Mostly decomposer
- Helpful in making curd from milk
- Produce antibiotics
- Symbiotically associated with leguminous plant and fix nitrogen.
- Some are pathogen causing diseases like cholera, typhoid, and tetanus.
- Bacteria reproduce mainly by fission, also produce spore in unfavorable condition.
- Reproduce sexually by transfer of DNA form one bacteria to other, the process called conjugation.
Mycoplasma :
- Completely lack cell wall.
- Smallest living cells.
- Can survive without oxygen.
- Pathogenic in animals and plants.
Kingdom Protista :
- All are unicellular and eukaryotic.
- Mostly aquatic, can live in moist places.
- Forms a link between plants, animals and fungi.
- The cell contain nucleus and membrane bound organelles.
Chrysophytes :
- Includes diatoms and golden algae (desmids)
- Found in freshwater or marine water.
- Mostly planktonic ( passive swimmer)
- Photosynthetic.
- Cell walls overlap to fit together like a soap box.
- Cell wall contains silica hence indestructible.
- Their accumulation forms ‘Diatomaceous Earth’.
- Used in polishing, filtration of oils and syrups.
- Diatoms are the chief ‘producers’ in the oceans.
Dinoflagellates :
- Marine, photosynthetic.
- Cell wall has stiff cellulose plates.
- Appears yellow, green, brown, blue or red depending on the pigments.
- Have two flagella − one longitudinal and other transversely in a furrow between wall plates.
- Red Dinoflagellates (Gonyaulax) form red tides.
