Topic summary
Endosymbiotic Theory
Extracted from the Wikipedia article Symbiogenesis.
Endosymbiosis of protomitochondria
Endosymbiotic theory for the origin of mitochondria suggests that the proto-eukaryote engulfed a protomitochondrion, and this endosymbiont became an organelle, a major step in eukaryogenesis, the creation of the eukaryotes.