Domain (biology)

In biological taxonomy, a domain (/dəˈmeɪn/ or /doʊˈmeɪn/) (Latin: regio[1]), also dominion,[2] superkingdom, realm, or empire, is the highest taxonomic rank of all organisms taken together.

The term domain was proposed by Carl Woese, Otto Kandler, and Mark Wheelis (1990) in a three-domain system.

[2] Carl Linnaeus made the classification "domain" popular in the famous taxonomy system he created in the middle of the eighteenth century.

This system was further improved by the studies of Charles Darwin later on but could not classify bacteria easily, as they have very few observable features to compare to the other domains.

[5] Carl Woese made a revolutionary breakthrough when, in 1977, he compared the nucleotide sequences of the 16s ribosomal RNA and discovered that the rank "domain" contained three branches, not two as scientists had previously thought.

[1] Archaea are prokaryotic cells, typically characterized by membrane lipids that are branched hydrocarbon chains attached to glycerol by ether linkages.

[1] Members of the domain Eukarya – called eukaryotes – have membrane-bound organelles (including a nucleus containing genetic material) and are represented by five kingdoms: Plantae, Protozoa, Animalia, Chromista, and Fungi.

Life Domain Kingdom Phylum Class Order Family Genus Species
The hierarchy of biological classification 's eight major taxonomic ranks . Life is divided into domains, which are subdivided into further groups. Intermediate minor rankings are not shown.
Bacteria Archaea Eukaryota Aquifex Thermotoga Bacteroides–Cytophaga Planctomyces "Cyanobacteria" Proteobacteria Spirochetes Gram-positives Chloroflexi Thermoproteus–Pyrodictium Thermococcus celer Methanococcus Methanobacterium Methanosarcina Haloarchaea Entamoebae Slime molds Animals Fungi Plants Ciliates Flagellates Trichomonads Microsporidia Diplomonads
A speculatively rooted tree for RNA genes , showing major branches Bacteria, Archaea, and Eukaryota
The three-domain tree and the eocyte hypothesis (two-domain tree), 2008. [ 7 ]
Phylogenetic tree showing the relationship between the eukaryotes and other forms of life, 2006. [ 8 ] Eukaryotes are colored red, archaea green, and bacteria blue.