Monera

Monera (/məˈnɪərə/ mə-NEER-ə) is a kingdom that contains unicellular organisms without a nucleus (i.e., a prokaryotic cell organization), such as bacteria. The kingdom is considered superseded.

The taxon Monera was first proposed as a phylum by Ernst Haeckel in 1866. Subsequently, the taxon was elevated to the rank of kingdom in 1925 by Édouard Chatton. The last commonly accepted mega-classification with the taxon Monera was the five-kingdom classification system established by Robert Whittaker in 1969.

Under the three-domain system of taxonomy, which was established in 1980 and reflects the evolutionary history of life as currently understood, the organisms found in kingdom Monera have been divided into two domains, Archaea and Bacteria (with Eukarya as the third domain). Furthermore the taxon Monera is paraphyletic. The term "moneran" is the informal name of members of this group and is still sometimes used (as is the term "prokaryote") to denote a member of either domain.

Despite the fact that most bacteria were classified under Monera, the bacterial phylum Cyanobacteria (the blue-green algae) was not initially classified under Monera, but under Plantae because of the ability of its members to photosynthesise.