Two-empire system
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The two-empire system (two-superkingdom system) was the top-level biological classification system in general use before the establishment of the three-domain system. It classified life into Prokaryota and Eukaryota. When the three-domain system was introduced, some biologists preferred the two-superkingdom system, claiming that the three-domain system overemphasized the division between Archaea and Bacteria. However, given the current state of knowledge and the rapid progress in biological scientific advancement, especially due to genetic analyses, that view has all but vanished.
| Two superdomains | Three domains | Six kingdoms | ||
|---|---|---|---|---|
| Biota / Vitae life |
Acytota / Aphanobionta (Viruses, Viroids, Prions?, ...) non-cellular life | |||
| Cytota cellular life |
Prokaryota / Procarya (Monera) |
Bacteria | Eubacteria | |
| Archaea | Archaebacteria | |||
| Eukaryota / Eukarya | Protista | |||
| Fungi | ||||
| Plantae | ||||
| Animalia | ||||
This system was preceded by Haeckel's three-kingdom system: Animalia – Plantae – Protista
