Summary of Biological Classification

Summary of Biological Classification

 

  •  The biological classification of plants and animals was first proposed  by Aristotle on the basis of simple morphological characters.  Linnaeus later classified all living organisms into two kingdoms  – Plantae and Animalia.
  •  An elaborate five-kingdom classification was proposed by  Whittaker – Monera, Protista, Fungi, Plantae, and Animalia.
  •  The main criteria of the five kingdom classifications were cell structure, body organization, mode of nutrition and reproduction, and phylogenetic relationships.
  •  In the five kingdom classifications, bacteria are included in Kingdom Monera. Bacteria are cosmopolitan in distribution.
  •  These organisms show the most extensive metabolic diversity.  Bacteria may be autotrophic or heterotrophic in their mode of nutrition.
  •  Kingdom Protista includes all single-celled eukaryotes such as   Chrysophytes, Dinoflagellates, Euglenoids, Slime-moulds, and Protozoans.
  •  Protists have defined nucleus and other membrane-bound organelles. They reproduce both asexually and sexually.
  •  Members of Kingdom Fungi show a great diversity in structures and habitat.
  •  Most fungi are saprophytic in their mode of nutrition.
  •  They show asexual and sexual reproduction.
  •  Phycomycetes, Ascomycetes, Basidiomycetes, and   Deuteromycetes are the four classes under this kingdom.
  •  The Plantae includes all eukaryotic chlorophyll-containing organisms.
  •  Algae, bryophytes, pteridophytes, gymnosperms, and angiosperms are included in this group.
  •  The life cycle of plants exhibits an alternation of generations –  gametophytic and sporophytic generations.
  •  The heterotrophic eukaryotic, multicellular organisms lacking a  cell wall are included in the Kingdom Animalia.
  • The mode of nutrition of these organisms is holozoic. They reproduce mostly by the sexual mode. Some acellular organisms like viruses and viroids as well as the lichens are not included in the five kingdom system of classification.