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The three-domain system is a biological classification introduced by Carl Woese
Carl Woese

Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of Svedberg ribosome RNA, a technique pioneered by Woese and which is now standard practice....
 in 1990 that divides cellular life forms into archaea
Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
, bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
, and eukaryote
Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
 domain
Domain (biology)

In Biology taxonomy, a domain is the highest taxonomic rank of organisms, higher than a Kingdom . According to the three-domain system of Carl Woese, introduced in 1990, the Tree of life consists of three domains: Archaea, Bacteria and Eukaryota....
s. In particular, it emphasizes the separation of prokaryote
Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other cell membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus....
s into two groups, originally called Eubacteria and Archaebacteria. Woese argued that, on the basis of differences in 16S rRNA gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s, these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic
Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
 machinery, often called a progenote.






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The three-domain system is a biological classification introduced by Carl Woese
Carl Woese

Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of Svedberg ribosome RNA, a technique pioneered by Woese and which is now standard practice....
 in 1990 that divides cellular life forms into archaea
Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . Archaea, like bacteria, are prokaryotic....
, bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
, and eukaryote
Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
 domain
Domain (biology)

In Biology taxonomy, a domain is the highest taxonomic rank of organisms, higher than a Kingdom . According to the three-domain system of Carl Woese, introduced in 1990, the Tree of life consists of three domains: Archaea, Bacteria and Eukaryota....
s. In particular, it emphasizes the separation of prokaryote
Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other cell membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus....
s into two groups, originally called Eubacteria and Archaebacteria. Woese argued that, on the basis of differences in 16S rRNA gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s, these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic
Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
 machinery, often called a progenote. To reflect these primary lines of descent, he treated each as a domain, divided into several different kingdom
Kingdom (biology)

In Biology taxonomy, kingdom or regnum is a taxonomic rank in either the highest rank, or the Rank below domain . Each kingdom is divided into smaller groups called Phylum ....
s.

Classification


Niches


Each of the three cell types tends to fit into recurring specialties or roles. Bacteria tend to be the most prolific reproducers, at least in moderate environments. Archaeans tend to adapt quickly to extreme environments, such as high temperatures, high acids, high sulfur, etc. This includes adapting to use a wide variety of food sources. Eukaryotes are the most flexible with regard to forming cooperative colonies, such as in multi-cellular organisms, including humans. In fact, the structure of a Eukaryote itself may have derived from a joining of different cell types, forming organelle
Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
s.

See also


  • Phylogenetic tree
    Phylogenetic tree

    A phylogenetic tree or evolutionary tree is a tree showing the evolutionary relationships among various biological species or other entities that are believed to have a common descent....
  • Taxonomy
    Taxonomy

    Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
  • Two-empire system
    Two-empire system

    The two-empire system was the top-level biological classification system in general use before the establishment of the three-domain system. It classified cellular life into Prokaryota and Eukaryota....
  • Five-kingdom system
  • Monera
    Monera

    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 , on the other hand, is held in the cell's nucleus....