Three domains systejn or six kingdom classification is a
living
biological classification system in which
organisms were divided based on cellular characteristics.
Carl Woese in 1990 introduced it.
The three domains are
(i) Archaea It contains prokaryotic organisms, which
have a monolayer core of lipids in the cell membrane
and distinct nucleotides in their 16 S RNA.
(ii) Bacteria It contains typical prokaryotes, which lack
membrane covered cell organelles but do not have a
of microchambers for separating various activities.
(iii) Eukarya This domain contains eukaryotic organisms,
originated by endosymbiotic association between some
archaebacteria and eubacteria.
It have four
kingdoms—Protista, Fungi, Plantae and Animalia.