Domains: The tree of life groups all living organisms based on evolutionary relationships
into large, inclusive groups, primarily based on the presence or absence of a nucleus within the
cell. The largest taxonomic group is called the domain. The two groups of prokaryotic
organisms are so different from each other that they are grouped into different domains. So the
original concept that all bacteria (prokaryotic organisms) should be classified in the same
kingdom (called Monera) has been altered. The three domains are: Archea (prokaryotic),
Bacteria (prokaryotic) and Eukarya (includes the kingdoms Protista, Fungi, Plantae and
Animalia).