Difference between revisions of "Monera" - New World Encyclopedia

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[[Image:5kingdoms.png|thumb|right|Figure 1. Five kingdoms.]]
 
[[Image:5kingdoms.png|thumb|right|Figure 1. Five kingdoms.]]
  
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'''Monera''' is an [[obsolete]] [[kingdom (biology)|biological kingdom]] that comprised most living things with a [[prokaryote|prokaryotic]] [[cell (biology)|cell]] organization (see [[Bacteria]] and [[Archaea]]). For this reason the kingdom was sometimes called [[prokaryote|Prokaryotae]]. Prior to its creation these were treated as two separate divisions of [[plants]]: the Schizomycetes or [[bacterium|bacteria]], considered [[fungi]], and the [[Cyanophyta]] or blue-green [[algae]].  They later are now considered a group of [[bacteria]], typically called the [[cyanobacteria]], and are known not to be closely related to [[plant]]s, [[fungi]], or [[animal]]s. Recent [[DNA sequencing|DNA]] and [[RNA sequencing|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 [[Eukaryote]]s. All new schemes abandon the Monera and now treat the Bacteria, Archaea, and [[Eukaryote|Eukarya]] as separate domains or kingdoms.
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'''Monera''', in some systems of [[Taxonomy#Scientific or biological classification|biological classification]], is a [[taxonomy#Domain and Kingdom systems|kingdom]] that comprises most living things with a [[prokaryote|prokaryotic]] [[cell (biology)|cell]] organization. For this reason, the kingdom also has been called Prokaryotae.
  
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Traditionally objects were classified as animal, vegetable or mineral (see: [[Systema Naturae]]). After the discovery of [[microscope|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<ref name="Haeckel">{{cite book|author = E. Haeckel|title = Generelle Morphologie der Organismen|publisher = Reimer, Berlin|year = 1866}}</ref>. Later, Haeckel proposed the fourth kingdom of which he called Monera. 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 the Monera had proven to be too diverse to be seriously considered one single kingdom.
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Kingdom Monera historically included the [[bacteria]], [[cyanobacteria|blue-green algae]] (cyanobacteria or blue-green bacteria), and the [[archaebacteria]] (Towle 1989). At times, four phyla of Kingdom Monera were recognized: Archaebacteria, Schizopyta (bacteria), Cyanophyta (the phytosynthetic cyanobacteria), and Prochlorophyta (symbiotic photosynthetic bacteria). However, the unique nature of the archaebacteria has led to classifications where they are not included with Monera.
  
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In 1969 [[Robert Whittaker]] published a proposed five kingdom system (Figure 1) for classification of living organisms<ref name="Whittaker1969">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 (journal)|Science]]'' Volume 163, pages 150-160. {{Entrez Pubmed|5762760}}</ref>. 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, Animals and Plants.
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In the five kingdom system of biological classification, the other kingdoms are [[Protista]], [[Fungi]], [[Plantae]], and [[Animalia]]. In the six kingdom system, the archaebacteria are separated into their own kingdom, Archaebacteria or [[Archaea]].  
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[[Image:Phylogenetic_tree.svg|thumb|right|260px|Figure 2. A [[phylogenetic tree]] of living things, based on [[rRNA]] sequence data, showing the separation of [[bacterium|bacteria]], [[archaea]], and [[eukaryote]]s.]]
 
  
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The history of the classification of bacteria and archaebacteria, and the use of the category Monera, reveals the nature of taxonomy (like science) to be dynamic, including clashes of doctrine and competing groups. Recently, this has manifested in a taxonomy where both Monera and, to a degree, the kingdom system are considered obsolete.
  
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{{biological systems}}
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Although the kingdom level traditionally was the highest level, since 1990, a higher classification level has been promoted called a "domain" or "superkingdom." It includes three major groups: The Archaea, Bacteria, and [[Eukaryote|Eukaryota]]. Some place Monera as a kingdom under the domain Bacteria; however, in originator Carl Woese's popular three-domain system, Monera no longer exists, as life is divided into multiple main divisions incorporated within the three domains Bacteria, Archaea, and Eukarya.
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==Monera in biological classification==
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For two centuries, from the mid-eighteenth century until the mid-twentieth century, organisms were generally considered to belong to one of two kingdoms, [[Plant|Plantae]] (plants, including bacteria) or [[Animal|Animalia]] (animals, including protozoa). This system was proposed by Carolus Linnaeus in the mid-18th century. However, this classification had obvious difficulties, including the problem of placing [[fungus|fungi]], [[protist]]s, and [[prokaryote]]s. There are single-celled organisms that fall between the two categories, such as ''Euglena,'' that can photosynthesize food from sunlight and yet feed by consuming organic matter.
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In 1866, [[Ernst Haeckel]] proposed a three kingdom system that added [[Protista]] as a new kingdom that contained most microscopic organisms (Haeckel 1866). 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 [[eukaryote|eukaryotic]] organisms now classified as [[Protist]]. Later, Haeckel proposed a fourth kingdom, which he called Monera. It was later decided that Monera proved to be too diverse to be seriously considered one single kingdom.
 +
 
 +
In 1969, [[Robert Whittaker]] published a proposed five kingdom system (Figure 1) for classification of living organisms (Whittaker 1969). Whittaker's system placed most single celled organisms into either the Monera ([[prokaryotes]]&mdash;bacteria and [[cyanobacteria|blue-green algae]]) or the Protista ([[eukaryote]]s). The other three kingdoms in his system were the eukaryotic Fungi, Animals, and Plants.  This system was widely used for three decades, and remains popular today.
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[[Image:Phylogenetic_tree.svg|thumb|right|260px|Figure 2. A phylogenetic tree of living things, based on [[rRNA]] sequence data, showing the separation of [[bacterium|bacteria]], [[archaea]], and [[eukaryote]]s.]] 
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The three-domain system was introduced by [[Carl Woese]] in 1990 (Woese et al. 1990). One of the reasons such a classification has been developed is because research has revealed the unique nature of anaerobic bacteria (called Archaeobacteria, or simply Archaea). These "living fossils" are genetically and metabolically very different from oxygen-breathing organisms (Woese 1987). Based on molecular phylogeny studies, Woese proposed that the prokaryotes (monerans) be divided into two separate groups: Bacteria and Archaea. This gave three groupings: [[Archaea]], [[Bacterium|Bacteria]], and [[Eukaryote|Eukaryota]] or Eukarya.
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In his 1990 proposed phylogeny (Woese et al. 1990), these three domains are all rooted in a universal common ancestor that Woese (1987) had speculated on earlier. This proposed phylogeny is the most widely accepted categorical phylogeny accepted today (see diagram to the right). However, the most modern interpretation for these three domains is the "Universal and Eukaryote Phylogenetic Tree" based on 16s rDNA as presented on the Tree of Life website (Sogin 2006).
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Some maintain the five-kingdom classification ''under'' the higher-level "domain" category. However, Woese's three domain system, based upon genetic relationships rather than obvious morphological similarities, divides life into 23 main divisions, all incorporated within the three domains of Bacteria, Archaea, and Eukarya. In this scheme, Kingdom Monera no longer exists.
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There are additional systems of biological classification in use. Some authorities, who recognize a need to separate bacteria and archaebacteria, nonetheless keep the kingdom system as the highest level classification, but add a sixth kingdom, the Archaebacteria. In this six-kingdom system, the Kingdom Monera remains. 
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Coexisting with these schemes is one dividing living organisms into the two main divisions of [[prokaryote]] (cells that lack a nucleus: Bacteria, etc.) and [[eukaryote]] (cells that have a nucleus and membrane-bound organelles: Animals, plants, fungi, and protists).
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Thus, today there are several competing top classifications of [[life]]:
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*The three-domain system of Carl Woese, with top level groupings of [[Archaea]], [[Eubacteria]], and [[Eukaryota]] domains
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*The two-empire system, with top level groupings of [[Prokaryota]] (or [[Monera]]) and [[Eukaryota]] empires
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*The five-kingdom system with top level groupings of [[Monera]], [[Protista]], [[Fungi]], [[Plantae]], and [[Animalia]]
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*The six-kingdom system with top level groupings of [[Archaebacteria]], [[Monera]], [[Protista]], [[Fungi]], [[Plant|Plantae]], and [[Animal|Animalia]]
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Overall, the majority of biologists accept the domain system, but a large minority uses the five-kingdom method. A small minority of scientists adds Archaea or Archaebacteria as a sixth kingdom but do not accept the domain method.
  
  
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Based on molecular phylogeny studies, [[Carl Woese]] proposed that the prokaryotes (monerans) be divided into two separate groups: Bacteria and Archaea. In Carl Woese's 1990 proposed phylogeny<ref name="Woese1990">"Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya" by C. R. Woese, O. Kandler, and M. L. Wheelis in [[Proceedings of the National Academy of Sciences|Proceedings of the National Academy of Sciences U.S.A.]] (1990) Volume 87, pages 4576-4579. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=2112744 Full text online].</ref>, these three kingdoms are all rooted in a universal common ancestor and this is the most widely accepted categorical phylogeny accepted today (see diagram to the right). However, the most modern interpretation for these three kingdoms is the "Universal and Eukaryote Phylogenetic Tree" based on 16s rDNA as presented on the Tree of Life website<ref name="Sogin2006">"Universal and Eukaryote trees Based on 16s rDNA." by Mitchell L. Sogin (2006) [http://tolweb.org/notes/?note_id=54 Tree of Life website].</ref>.
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{{biological systems}}
  
 
==References==
 
==References==
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<div class="references-small">
 
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<references />
 
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</div>
 
  
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==See also==
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* Haeckel, E. 1866. ''Generelle Morphologie der Organismen''. Berlin: Reimer.
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*[[Bacterial cell structure]]
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* Sogin, M. L. 2006. Universal and eukaryote trees based on 16s rDNA. ''Tree of Life Website''.
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*[[Kingdom (biology)]]
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* Whittaker, R. 1969. New concepts of kingdoms or organisms: Evolutionary relations are better represented by new classifications than by the traditional two kingdoms. ''Science'' 163: 150-160.
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Monera also  called Prokayotae it is the kingdom of prokaryotic organisms that are unicellular  that is a single-celled: consisting of a single cell & lack a true cell nucleus.
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* Woese, C. R. 1987. [http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=2439888 Bacterial evolution]. ''Microbiological Reviews'' 51(2):221-271.
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* Woese, C. R., O. Kandler, and M. L. Wheelis. 1990. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=2112744 Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya]. ''Proceedings of the National Academy of Sciences U.S.A.'' 87: 4576-4579.  
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==External links==
 
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*[http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=2439888 Bacterial evolution] by [[Carl Woese]] (1987). Woese reviewed the historical steps leading to the use of the term "Monera" and its later abandonment (full text online). {{Entrez Pubmed|2439888}}
 
  
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]
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[[Category:Prokaryotes]]
 
{{credit|102576834}}
 
{{credit|102576834}}

Latest revision as of 13:09, 10 March 2023

Figure 1. Five kingdoms.

Monera, in some systems of biological classification, is a kingdom that comprises most living things with a prokaryotic cell organization. For this reason, the kingdom also has been called Prokaryotae.

Kingdom Monera historically included the bacteria, blue-green algae (cyanobacteria or blue-green bacteria), and the archaebacteria (Towle 1989). At times, four phyla of Kingdom Monera were recognized: Archaebacteria, Schizopyta (bacteria), Cyanophyta (the phytosynthetic cyanobacteria), and Prochlorophyta (symbiotic photosynthetic bacteria). However, the unique nature of the archaebacteria has led to classifications where they are not included with Monera.

In the five kingdom system of biological classification, the other kingdoms are Protista, Fungi, Plantae, and Animalia. In the six kingdom system, the archaebacteria are separated into their own kingdom, Archaebacteria or Archaea.

The history of the classification of bacteria and archaebacteria, and the use of the category Monera, reveals the nature of taxonomy (like science) to be dynamic, including clashes of doctrine and competing groups. Recently, this has manifested in a taxonomy where both Monera and, to a degree, the kingdom system are considered obsolete.

Although the kingdom level traditionally was the highest level, since 1990, a higher classification level has been promoted called a "domain" or "superkingdom." It includes three major groups: The Archaea, Bacteria, and Eukaryota. Some place Monera as a kingdom under the domain Bacteria; however, in originator Carl Woese's popular three-domain system, Monera no longer exists, as life is divided into multiple main divisions incorporated within the three domains Bacteria, Archaea, and Eukarya.

Monera in biological classification

For two centuries, from the mid-eighteenth century until the mid-twentieth century, organisms were generally considered to belong to one of two kingdoms, Plantae (plants, including bacteria) or Animalia (animals, including protozoa). This system was proposed by Carolus Linnaeus in the mid-18th century. However, this classification had obvious difficulties, including the problem of placing fungi, protists, and prokaryotes. There are single-celled organisms that fall between the two categories, such as Euglena, that can photosynthesize food from sunlight and yet feed by consuming organic matter.

In 1866, Ernst Haeckel proposed a three kingdom system that added Protista as a new kingdom that contained most microscopic organisms (Haeckel 1866). 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. Later, Haeckel proposed a fourth kingdom, which he called Monera. It was later decided that Monera proved to be too diverse to be seriously considered one single kingdom.

In 1969, Robert Whittaker published a proposed five kingdom system (Figure 1) for classification of living organisms (Whittaker 1969). Whittaker's system placed most single celled organisms into either the Monera (prokaryotes—bacteria and blue-green algae) or the Protista (eukaryotes). The other three kingdoms in his system were the eukaryotic Fungi, Animals, and Plants. This system was widely used for three decades, and remains popular today.

Figure 2. A phylogenetic tree of living things, based on rRNA sequence data, showing the separation of bacteria, archaea, and eukaryotes.

The three-domain system was introduced by Carl Woese in 1990 (Woese et al. 1990). One of the reasons such a classification has been developed is because research has revealed the unique nature of anaerobic bacteria (called Archaeobacteria, or simply Archaea). These "living fossils" are genetically and metabolically very different from oxygen-breathing organisms (Woese 1987). Based on molecular phylogeny studies, Woese proposed that the prokaryotes (monerans) be divided into two separate groups: Bacteria and Archaea. This gave three groupings: Archaea, Bacteria, and Eukaryota or Eukarya.

In his 1990 proposed phylogeny (Woese et al. 1990), these three domains are all rooted in a universal common ancestor that Woese (1987) had speculated on earlier. This proposed phylogeny is the most widely accepted categorical phylogeny accepted today (see diagram to the right). However, the most modern interpretation for these three domains is the "Universal and Eukaryote Phylogenetic Tree" based on 16s rDNA as presented on the Tree of Life website (Sogin 2006).

Some maintain the five-kingdom classification under the higher-level "domain" category. However, Woese's three domain system, based upon genetic relationships rather than obvious morphological similarities, divides life into 23 main divisions, all incorporated within the three domains of Bacteria, Archaea, and Eukarya. In this scheme, Kingdom Monera no longer exists.

There are additional systems of biological classification in use. Some authorities, who recognize a need to separate bacteria and archaebacteria, nonetheless keep the kingdom system as the highest level classification, but add a sixth kingdom, the Archaebacteria. In this six-kingdom system, the Kingdom Monera remains.

Coexisting with these schemes is one dividing living organisms into the two main divisions of prokaryote (cells that lack a nucleus: Bacteria, etc.) and eukaryote (cells that have a nucleus and membrane-bound organelles: Animals, plants, fungi, and protists).

Thus, today there are several competing top classifications of life:

Overall, the majority of biologists accept the domain system, but a large minority uses the five-kingdom method. A small minority of scientists adds Archaea or Archaebacteria as a sixth kingdom but do not accept the domain method.


Linnaeus
1735
2 kingdoms 		Haeckel
1866
3 kingdoms 		Chatton
1937
2 empires 		Copeland
1956
4 kingdoms 		Whittaker
1969
5 kingdoms 		Woese et al.
1977
6 kingdoms 		Woese et al.
1990
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


References
ISBN links support NWE through referral fees

  • Haeckel, E. 1866. Generelle Morphologie der Organismen. Berlin: Reimer.
  • Sogin, M. L. 2006. Universal and eukaryote trees based on 16s rDNA. Tree of Life Website.
  • Whittaker, R. 1969. New concepts of kingdoms or organisms: Evolutionary relations are better represented by new classifications than by the traditional two kingdoms. Science 163: 150-160.
  • Woese, C. R. 1987. Bacterial evolution. Microbiological Reviews 51(2):221-271.
  • Woese, C. R., O. Kandler, and M. L. Wheelis. 1990. Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. Proceedings of the National Academy of Sciences U.S.A. 87: 4576-4579.

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