(Chatton, 1925) Whittaker & Margulis, 1978
|Supergroups and kingdoms|
Eukaryota, whose members are known as eukaryotes (/juːˈkærioʊts, -əts/), is a diverse domain of organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of living things, along with the two groups of prokaryotes, the Bacteria and the Archaea.
The eukaryotes emerged in the Archaea, possibly within the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is about equal to that of prokaryotes. Eukaryotes emerged approximately 2.2 billion years ago, during the Proterozoic eon, likely as flagellated cells. These were created by symbiogenesis between an anaerobic Asgard archaean and an aerobic proteobacterium, which formed the mitochondria. A second episode of symbiogenesis with a cyanobacterium created the plants, with chloroplasts. The oldest-known eukaryote fossils, multicellular planktonic organisms belonging to the Gabonionta, were discovered in Gabon in 2023, dating back to 2.1 billion years ago.
Eukaryotic cells contain membrane-bound organelles such as the nucleus, the endoplasmic reticulum, and the Golgi apparatus. Eukaryotes may be either unicellular or multicellular. In comparison, prokaryotes are typically unicellular. Unicellular eukaryotes are sometimes called protists. Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion.
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