Monera

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Figure 1. Five kingdoms. The eukaryotes ("true cells") are now said to comprise one related domain, while the monera comprise the other two: bacteria and archaea.
Figure 1. Five kingdoms. The eukaryotes ("true cells") are now said to comprise one related domain, while the monera comprise the other two: bacteria and archaea.

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.

Recent DNA and RNA sequence analyses has demonstrated that there are two major groups of prokaryotes, the Bacteria and Archaea, which do not appear to be closer in relationship to each other than they are to the Eukaryotes. Thus, 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.



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[edit] History

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.

In 1969, Robert Whittaker published a proposed five kingdom system for classification of living organisms.[2] Whittaker's system placed most single celled organisms into either the prokaryotic Monera or the eukaryotic Protista. The other three kingdoms in his system were the eukaryotic Fungi, Animalia, and Plantae.

[edit] Summary

Linnaeus
1735
2 kingdoms		 Haeckel
1866[1]
3 kingdoms		 Chatton
1937[3]
2 empires		 Copeland
1956[4]
4 kingdoms		 Whittaker
1969[2]
5 kingdoms		 Woese et al.
1977[5]
6 kingdoms		 Woese et al.
1990[6]
3 domains
(not treated) Protista Prokaryota Monera Monera Eubacteria Bacteria
Archaebacteria Archaea
Eukaryota Protista Protista Protista Eukarya
Vegetabilia Plantae Fungi Fungi
Plantae Plantae Plantae
Animalia Animalia Animalia Animalia Animalia


[edit] References

  1. ^ a b E. Haeckel (1867). Generelle Morphologie der Organismen. Reimer, Berlin. 
  2. ^ a b Robert Whittaker (1969) "New concepts of kingdoms or organisms. Evolutionary relations are better represented by new classifications than by the traditional two kingdoms" in Science Volume 163, pages 150-160. Entrez PubMed 5762760
  3. ^ E. Chatton (1937). Titres et travaux scientifiques. Sette, Sottano, Italy. 
  4. ^ H. F. Copeland (1956). The Classification of Lower Organisms. Palo Alto: Pacific Books. 
  5. ^ C. R. Woese, W. E. Balch, L. J. Magrum, G. E. Fox and R. S. Wolfe (1977). "An ancient divergence among the bacteria". Journal of Molecular Evolution 9: 305–311. 
  6. ^ Carl R. Woese, Otto Kandler, Mark L. Wheelis: "Towards a Natural System of Organisms: Proposal for the domains Archaea, Bacteria, and Eucarya", doi:10.1073/pnas.87.12.4576

[edit] See also

[edit] External links