All Prokaryote Domains

The prokaryote domains are Bacteria and Archaea, the two lineages into which the old Prokaryotae are now divided. They are as different from each other as either is from the third domain, the Eukaryota, and none of the three is ancestral to the others, although each shares certain features with the others and has unique characteristics of its own. Work showing that what had been called prokaryotes are far more diverse than anyone suspected led to this split. Until recently living organisms were divided into two kingdoms, animal and vegetable, and the scheme most often used afterward grouped all bacteria in a single kingdom, Monera.