In biological taxonomy, a domain ( or ) ( latin : regio [ 1 ] ), besides dominion, [ 2 ] superkingdom, realm, or empire, [ 3 ] is the highest taxonomic rank of organisms in the three-domain system of taxonomy devised by Carl Woese et alabama. in 1990. [ 1 ] According to this arrangement, the tree of life consists of three domains : Archaea, Bacteria, and Eukarya. [ 1 ] The first two are all prokaryotic microorganisms, or largely single-celled organisms whose cells have a distorted or non-membrane bandaged nucleus. All life that has a cell nucleus and eukaryotic membrane-bound organelles is included in Eukarya.
Reading: Domain (biology) – Flickroom
Non-cellular life is not included in this system. Alternatives to the three-domain system include the earlier two-empire system ( with the empires Prokaryota and Eukaryota ), and the eocyte guess ( with two domains of Bacteria and Archaea, and Eukarya included within Archaea ) .
The term “ knowledge domain ” was proposed by Carl Woese, Otto Kandler and Mark Wheelis ( 1990 ) in a three-domain system. This term represents a synonym for the category of dominion ( Lat. dominium ), introduced by Moore in 1974. [ 2 ]
Characteristics of the three domains
A speculatively rooted corner for RNA genes, showing major branches Bacteria, Archaea, and Eukaryota  Eukaryotes are colored red, archaea green, and bacteria blue.Phylogenetic tree showing the relationship between the eukaryotes and other forms of life, 2006Eukaryotes are colored red, archaea green, and bacteria blue. Each of these three domains contains alone rRNA. This forms the footing of the three-domain system. While the presence of a nuclear membrane differentiates the Eukarya from the Archaea and Bacteria, both of which lack a nuclear membrane, distinct biochemical and RNA markers differentiate the Archaea and Bacteria from each other. [ 1 ]
Archaea are prokaryota cells, typically characterized by membrane lipids that are branched hydrocarbon chains attached to glycerol by ether linkages. The presence of these ether linkages in Archaea adds to their ability to withstand extreme point temperatures and highly acidic conditions, but many archaea live in meek environments. Halophiles, organisms that boom in highly piquant environments, and hyperthermophiles, organisms that thrive in highly hot environments, are examples of Archaea. [ 1 ]
Archaea evolved many cell sizes, but all are relatively small. Their size ranges from 0.1 μm to 15 μm diameter and up to 200 μm long. They are about the size of bacteria, or similar in size to the mitochondrion found in eukaryotic cells. Members of the genus Thermoplasma are the smallest of the Archaea. [ 1 ]
even though bacteria are prokaryotic cells good like Archaea, their membranes are made of phospholipid bilayers. Cyanobacteria and mycoplasmas are two examples of bacteria. They characteristically do not have ether linkages like Archaea, and they are grouped into a different category—and hence a unlike sphere. There is a great distribute of diverseness in this domain. Confounded by that diversity and horizontal gene transfer, it is following to impossible to determine how many species of bacteria exist on the planet, or to organize them in a tree-structure, without cross-connections between branches. [ 1 ]
Members of the knowledge domain Eukarya—called eukaryotes—have membrane-bound organelles ( including a nucleus contain genic material ) and are represented by five kingdoms : Plantae, Protozoa, Animalia, Chromista, and Fungi. [ 1 ]
exclusion of viruses and prions
The three-domain system does not include any form of non-cellular life. Stefan Luketa proposed a five-domain system in 2012, adding Prionobiota ( noncellular and without nucleic acid ) and Virusobiota ( noncellular but with nucleic acidic ) to the traditional three domains. [ 6 ]
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See also: Virus classification
Alternative classifications of animation include :