System of classification ( diversity -2)

Artificial system of classification:
These system of classification were based on size, color or nature of the organism. It is helpful in quick identification of the organism.Aristotle classified the organisms on the basis of nature of their habitat ie terrestrial, aquatic or arboreal.Theophrastus classified known plants on the basis of their form, life span and habitat into four categories- trees, herbs and shrubs.The drawback of these system were that closely related organisms got separated into different groups while unrelated organisms got grouped together.

ARISTOTLE

THEOPHRASTUS

E.H.HAECKEL

WHITTAKER

Natural system of classification: These systems were based on natural relationship between different organisms and indicated similarities and differences between the organisms. 

Two kingdom classification: Traditionally all organisms were divided into two kingdoms: animalia and plantae. Shortcomings: Fungi are non motile but non photosynthetic. Some algae on the other hand were motile .Euglena and chlamydomonas has features of both plants and animals.

Three kingdom classification: E.H. Haeckel suggested a third kingdom protista to include unicellular eukaryotic microorganisms.

Four kingdom classification: Copeland introduced the kingdom Monera for all prokaryotic organisms.

Five kingdom classification: Robert H. Whittaker divided the organisms into five kingdoms namely: monera, protista, fungi, plantae and animalia.

Six kingdom classification: Woese further divided bacteria into Archaebacteria and Eubacteria on the basis of cell wall composition.