Three domain classification was proposed by Carl Woese (1977) and his co-workers. They classified organisms based on the difference in 16s rRNA genes. This adds the taxon domain higher than the kingdom. In this system, prokaryotes are divided into two domains-bacteria and Arachaea.
All eukaryotes are placed under the domain Eukarya. Archae appears to have common features with Eukarya. Archaea differ from bacteria in cell wall composition and differ from bacteria and eukaryotes in membrane composition and RNA types.
