<P> The three - domain system is a biological classification introduced by Carl Woese et al. in 1977 that divides cellular life forms into archaea , bacteria , and eukaryote domains . In particular , it emphasizes the separation of prokaryotes into two groups , originally called Eubacteria ( now Bacteria ) and Archaebacteria ( now Archaea ) . Woese argued that , on the basis of differences in 16S rRNA genes , these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic machinery , often called a progenote . To reflect these primary lines of descent , he treated each as a domain , divided into several different kingdoms . Woese initially used the term `` kingdom '' to refer to the three primary phylogenic groupings , and this nomenclature was widely used until the term `` domain '' was adopted in 1990 . </P>
<P> The three - domain system is a biological classification introduced by Carl Woese et al. in 1977 that divides cellular life forms into archaea , bacteria , and eukaryote domains . In particular , it emphasizes the separation of prokaryotes into two groups , originally called Eubacteria ( now Bacteria ) and Archaebacteria ( now Archaea ) . Woese argued that , on the basis of differences in 16S rRNA genes , these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic machinery , often called a progenote . To reflect these primary lines of descent , he treated each as a domain , divided into several different kingdoms . Woese initially used the term `` kingdom '' to refer to the three primary phylogenic groupings , and this nomenclature was widely used until the term `` domain '' was adopted in 1990 . </P>
who determined archaea are the third domain of life
who determined archaea are the third domain of life
Carl Woese et al.
Carl Woese et al.