Lesson Overview Building the Tree of Life
Three Domains
Genetic analysis has revealed that the two main prokaryotic kingdoms
are more different from each other, and from eukaryotes, than
previously thought. So, biologists established a new taxonomic
category—the domain. A domain is a larger, more inclusive category
than a kingdom.
Under this system, there are three domains—domain Bacteria
(corresponding to domain Eubacteria), domain Archaea (corresponding
to kingdom Archaebacteria), and domain Eukarya (corresponding to
kingdoms Fungi, Plantae, Animalia, and kingdom “Protista”).
Quotes are put around kingdom “Protista” to indicate that it is not a
monophyletic group.