Kerala PSC - Study Material : Biology (Kingdom Classification)

Kerala PSC - Study Material : Biology (Kingdom Classification)

Classification is the arrangement of organisms into groups on the basis of similarities and differences among them.
  • Taxonomy is the science of Classification.
  • Linnaeus proposed the Two Kingdom Classification i.e. Plant and Animals.
  • Five kingdom classification was developed by R.H. Whittaker.
    1. Kingdom Monera are organisms with prokaryotic cells and diverse nutritional habits.
    2. Kingdom Protista are unicellular or colonial eukaryotes with diverse nutritional habits.
    3. Kingdom Fungi are multinucleate organisms with non-photosynthetic nutrition.
    4. Kingdom Plantae are multicellular autotrophic higher plants possessing cell-wall and chlorophyll.
    5. Kingdom Animalia are multicellular heterotropic organism without cellwalland chlorophyll.


  • Bacteria were first observed by Anton Van Leeuwenhoek in 1676.
  • Bacteria are microscopic unicellular prokaryotic organism characterized by the lack of a membrane bound nucleus and membrane bound organelles.
  • Bacteria are placed in Kingdom Monera.
  • Bacteriology is the study of bacteria.
  • According to shape, bacteria are classified into five they are:
    1. Cocci - spherical or oval cell
    2. Bacilli - rod shaped cell
    3. Vibrios - comma shaped, curved rodes.
    4. Spirilla - rigid spiral forms
    5. Spirochaetes - flexible spiral forms
  • Reproduction in bacteria is largely asexual by binary fission.
  • Sexual reproduction in bacteria is called conjugation.
  • Respiration of bacteria are aerobic and anaerobic.


  • Virus the term is coined by M.W. Beigerinck.
  • Virology is the study of viruses.
  • A virus is a small infectious agent that can replicate only inside the living cells of organisms.
  • All viruses are nucleoprotein particles and contain either DNA or RNA. The genetic material inside the virus is protected by a protein coat called 'capsid'.
  • A complete viral particle capable of infection is called a Virion.
  • Viroids are newly found group of pathogenic agents, much smaller than the viruses.
  • HIV is an RNA virus
  • Viruses having RNA as genetic material is known as retro viruses.
  • Bacteriophages are viruses eating (destroying) bacteria.


  • Fungi are eukaryotic organisms.
  • They are non-ascular organisms.
  • They reproduce by means of spores.
  • They are typically non-motile.
  • The vegetative body of the fungi may be unicellular or composed of microscopic threads called hyphae.
  • The structure of cell wall is similar to plants but chemically the fungi cell wall are composed of chitin.
  • Fungi are heterotrophic organisms.
  • Nutrition in fungi - they are saprophytes, or parasites or symbionts.
  • Reproduction in fungi is both by sexual and asexual means. Sexual state is referred to as teleomorph, asexual state is referred to as anamorph.
  • L.S.D (Lysergic acid diethylamide) is obtained from a fungi, called Ergot.
  • Many fungi are involved in symbiotic relationships.
  • Some fungi are parasites. They are specialized to penetrate a host and break down the host's tissues. Parasitic fungi often cause illness and may eventually kill their host.
  • Two common mutualistic relationships involving fungi are mycorrhiza (fungi and plant roots) and lichen (fungi and either cyanabacteria or green algae).
  • Some fungi also have mutualistic relationships with insects.

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