Temporal range: StatherianPresent
Scientific classification Edit this classification
Domain: Eukaryota
(Chatton, 1925) Whittaker & Margulis, 1978
Supergroups and kingdoms[2]

The eukaryotes (/jˈkærits, -əts/) constitute the domain of Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes: the Bacteria and 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 much larger than that of prokaryotes.

The eukaryotes seemingly emerged in the Archaea, within the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes emerged approximately 2.2 billion years ago, during the Proterozoic eon, likely as flagellated cells. The leading evolutionary theory is they 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 (fertilization).

  1. ^ Cite error: The named reference Provora was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference AdlBass2019 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference w1990 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Margulis 1996 was invoked but never defined (see the help page).

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