Editing Three-domain system (section)

{{short description|Hypothesis for classification of life}}
[[File:Phylogenetic tree of life 1990 LUCA.svg|thumb|upright=1.75|A [[phylogenetic tree]] based on [[Ribosomal RNA|rRNA]] data, emphasizing the separation of bacteria, archaea, and eukarya  as proposed by [[Carl Woese]] et al. in 1990,<ref name="w1990" /> with the hypothetical [[last universal common ancestor]]]]<!--Please note that the tree in PhylomapB is NOT the one that Woese et al actually proposed in 1990, see the image in their paper for yourself: someone has "improved" it with later accretions, making the caption false-->
The '''three-domain system''' is a [[taxonomy (biology)|taxonomic]] [[classification system]] that groups all [[cell (biology)|cell]]ular [[life]] into three [[domain (biology)|domain]]s, namely [[Archaea]], [[Bacteria]] and [[Eukarya]], introduced by [[Carl Woese]], [[Otto Kandler]] and [[Mark Wheelis]] in 1990.<ref name="w1990">{{cite journal | vauthors = Woese CR, Kandler O, Wheelis ML | title = Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 87 | issue = 12 | pages = 4576–9 | date = June 1990 | pmid = 2112744 | pmc = 54159 | doi = 10.1073/pnas.87.12.4576 | bibcode=1990PNAS...87.4576W| doi-access = free }}</ref> The key difference from earlier classifications such as the [[two-empire system]] and the five-kingdom classification is the splitting of Archaea (previously named "archaebacteria") from Bacteria as completely different organisms. 

The three domain hypothesis is considered obsolete by some since it is thought that eukaryotes do not form a separate domain of life; instead, they arose from a fusion between two different species, one from within Archaea and one from within Bacteria.<ref name="Gabaldón"/><ref name=":02">{{Cite journal |last1=Nobs |first1=Stephanie-Jane |last2=MacLeod |first2=Fraser I. |last3=Wong |first3=Hon Lun |last4=Burns |first4=Brendan P. |date=2022 |title=Eukarya the chimera: eukaryotes, a secondary innovation of the two domains of life? |url=https://linkinghub.elsevier.com/retrieve/pii/S0966842X21002699 |journal=Trends in Microbiology |volume=30 |issue=5 |pages=421–431 |doi=10.1016/j.tim.2021.11.003|pmid=34863611 |s2cid=244823103 |url-access=subscription }}</ref><ref name=":3">{{Cite journal |last=Doolittle |first=W. Ford |date=2020 |title=Evolution: Two Domains of Life or Three? |journal=Current Biology |volume=30 |issue=4 |pages=R177–R179 |doi=10.1016/j.cub.2020.01.010 |pmid=32097647 |doi-access=free |bibcode=2020CBio...30.R177D }}</ref> (see  [[Two-domain system]])