Classification Systems of Organisms

Classification Systems of Organisms

Two kingdom classification systems

  • It is the oldest system of classification
  • It divides organism in to two kingdoms, planate and animalia.
  • Plants are autotrophs because these can prepare food from simple organic materials.
  • Animalia are heterotrophs because these cannot prepare their food and depend upon other organism.
  • Bacteria, fungi and algae were included in to kingdom plantae.

Draw backs of two kingdom classification system

  • It not explains euglena like organisms because it is plant like as well as animal like.
  • It ignores difference between prokaryotes and eukaryotes.

 Three kingdom classification systems

  • It divides organisms in to three kingdoms, plantae,  animalia and Protista.
  • Kingdom protista was proposed by Ernst Hackel in 1866.
  • Protista include those organism which do not fit in to plantae or animalia i.e. Euglena

 Draw backs of three kingdom classification system

  • It ignores difference between prokaryotes and eukaryotes.
  • It places fungi in kingdom plantae, which is wrong. 

 Differences of fungi from plants and animals

  • It has cellulose in its cell wall.
  • It gets food by absorption.

   Five kingdom classification systems

  • It was introduced by Robert Whittaker in 1967.
  • It is based on levels of cellular organization and principal modes of nutrition.
  • It divides organisms in to five kingdoms, plantae,  animalia, Protista , fungi and Monera.
  • Kigdom monera have prokaryotic cell. Kingdom protista, fungi, plantae and animalia have eukaryotic cell

Kingdom Monera

  • It includes organisms formed by prokaryotic cells i.e bacteria and cyanobacteria.
  • Prokaryotic cells may be unicellular or form chains, cluster or colony.
  • Prokaryotic cells are different from eukaryoic cells.

Kingdom protista

  • It includes eukaryotic unicellular or multicellular organisms.
  • There are three types of protists.
  1. Algae: These are plant like protists. These have cell wall and chlorophyll. These are unicellular, colonial or multicellular.
  1. Protozoans: These are animal like protists.
  2. Fungus  like protists

Importance of kingdom protista 

Biologists believe that plants, animals and fungi are evolved from protista. Protists are evolved from monera.

Kingdom fungi

  • It includes eukaryotic multicellular, heterotrophic organisms which get food by absorption.
  • They live on organic matter and mostly are decompsers.
  • Its example is mushrooms.

Kingdom plantae

  • It includes eukaryotic, multicellular, autotrophic organisms. e.g mosses ,flowering plants etc.
  • Plants can make their own food by photosynthesis.
  • These have multicellular sex organs and form embryos.

Kingdom Animalia

  • It includes eukaryotic, multicellular, consumers. e.g. cow, earthworm etc.
  • Animals ingest food and digest in body cavities.
  • They show movements.

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