The Archaea [ɑrˈkiə] (help·info) are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon (sometimes spelled "archeon"). Archaea, like bacteria, are prokaryotes and have no cell nucleus or any other organelles within their cells. In the past they were viewed as an unusual group of bacteria and named archaebacteria but since the Archaea have an independent evolutionary history and show many...
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The Archaea [ɑrˈkiə] (help·info) are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon (sometimes spelled "archeon"). Archaea, like bacteria, are prokaryotes and have no cell nucleus or any other organelles within their cells. In the past they were viewed as an unusual group of bacteria and named archaebacteria but since the Archaea have an independent evolutionary history and show many differences in their biochemistry from other forms of life, they are now classified as a separate domain in the three-domain system. In this system, introduced by Carl Woese, the three main branches of evolutionary descent are the Archaea, Eukaryota and Bacteria. Archaea are further divided into four phyla of which two, the Crenarchaeota and the Euryarchaeota, are most intensively studied. Classifying the Archaea is still difficult, since the vast majority of these organisms have never been studied in the laboratory and have only been...
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