Domain

From EvoWiki

The taxonomic rank of domain was first proposed by Carl Woese in 1990, as a superrank of the kingdom; his Three Domains are:

• Eukarya - Eukaryotes
• Eubacteria / Bacteria - Prokaryotes that include most of the "familiar" bacteria
• Archaebacteria / Archaea - Prokaryotes that include various oddballs like methanogens

This taxonomy was originally a result of comparing small-subunit ribosomal RNA (SSU rRNA) sequences, sometimes called 16S rRNA or 18S rRNA on account of its ultracentrifuge sedimentation rate in Svedberg units (that "S"). Woese had selected it because it is both ubiquitous and strongly-conserved. However, it is supported by a variety of additional features.

Woese invented the name Archaebacteria, later Archaea, on the ground that many of this taxon's members are well-adapted to early-Earth conditions (Extremophiles). This is because many of them are anaerobic and many are also chemoautotrophic (making all their biomolecules from inorganic compounds like hydrogen, carbon dioxide, and sulfur, and also using various chemical reactions as an energy source).

Recent literature has tended to adopt the new domain system.

References

• The Tree of Life Project
• University of California Museum of Paleontology