Biological classification 4

THREE DOMAIN SYSTEM:

The current best classification is the three-domain system of Carl woese et al. in 1990.In above classifications we observed that organisms are classified into prokaryotes and eukaryotes. The new data shows that the prokaryotes were diverged early in the history of life, and thus there are the three major categories of organisms. They are Eubacteria, Archaea, and Eukarya. The prokaryotes were divided into domains Eubacteria and archaea while eukaryotes were classified into domain Eukarya. Carl woese classified based on difference of 18S/16S rRNA genes present in those domains.

Three domain system - Tree diagram

                                   

Tabular form of three domain system

                               

SIX KINGDOM SYSTEM:

          This is the most recent classification done by Carl woese, O Kandler, ML Wheelis in 1990. In this system the domain Eukarya includes four kingdoms- Protists, Fungi, Plantae and Animalia in which organisms are Eukaryotic. After comparison of the base sequences of 16S mRna variety of organisms these scientists proposed that the bacteria should be divided into two kingdoms namely Archaebacteria and Eubacteria. The organisms in these kingdoms are Prokaryotic organisms.

History of taxonomic concepts:

                               

Edouard chatton

1883 - 1947

Sydney W. Fox

1912 - 1998

                 



                  Courtesy by google images