Monera are bacteria and other mostly tiny, single-celled organisms whose genetic material is loose in the cell. The genetic material of
plants,
animals, and other
eukaryotes (
true nucleus), on the other hand, is held in the cell's nucleus. While the Monera were briefly understood to be one of
five biological kingdoms, it is now understood to comprise two kingdoms the eubacteria and the archaebacteria. The Monera kingdom included most organisms with a
prokaryotic cell organization (that is, no nucleus). For this reason, the kingdom was sometimes called
Prokaryota or
Prokaryotae.
Monera has since been divided into Archaea and Bacteria, forming the more recent six-kingdom system and three-domain system. All new schemes abandon the Monera and now treat the Bacteria, Archaea, and Eukarya as separate domains or kingdoms.
Prior to the five-kingdom model with its Monera kingdom, these organisms were classified as two separate divisions of plants the Schizomycetes (bacteria) were considered fungi, and the Cyanophyta were considered blue-green algae. The latter are now considered a group of bacteria, typically called the cyanobacteria and are now known not to be closely related to plants, fungi, or animals.
Traditionally organisms were classified as animal, vegetable, or mineral as in Systema Naturae. After the discovery of microscopy, attempts were made to fit microscopic organisms into either the plant or animal kingdom. In 1866 Ernst Haeckel proposed a three kingdom system which added Protista as a new kingdom that contained most microscopic organisms.[1] One of his eight major divisions of Protista was called Moneres. Haeckel's Moneres subcategory included known bacterial groups such as Vibrio. Haeckel's Protista kingdom also included eukaryotic organisms now classified as Protist. It was later decided that Haeckel's Protista kingdom had proven to be too diverse to be seriously considered one single kingdom.
