Prokaryote
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Prokaryotes are single-celled organisms without a
nucleus; i.e.
Bacteria and
Archaea. This name comes from the Greek root
karyon, meaning
nut, combined with the prefix
pro-, meaning
before. Organisms composed of cells with a nucleus are called
eukaryotes, where the prefix
eu- means
good or
true.
Prokaryotic life is ubiquitous on Earth, present in every conceivable
biome (and also being found in places where no life of any kind had been expected to exist, for example the endolithic biome). As such, there are prokaryotes with all manner of adaptations. Detailed treatments of prokaryotic structure can be found in the
bacteria and
archaea articles.
It is thought that the
first living cells on Earth were likely prokaryotic in structure, and possibly similar to some existing archaea. Fossil prokaryotes have been found in extremely ancient rocks on Earth. There was also a recent discovery of what may have been fossil prokaryotes in a
Martian meteorite, though this has since been disputed.
\nCategory:Microbiology
