Endosymbiosis

This process has its name from Greek: endom = inside and symbiosis = together living and describes that one organism lives inside another. This permanent coexistence, which supports both organisms, is common among the recent species on earth (e.g., algae live in the cells of corals). In the case of the Apicomplexa (e.g., species of the genera Toxoplasma , Sarcocystis , Eimeria , Isospora , Plasmodium ), even a secondary endosymbiosis occurs, since the so-called apicoplast represents a former red algae cell that had previously ingested another cell (Cyanobacterium), which is now retained as so-called chloroplast in its interior.

This endosymbiosis (double or single) is considered as the driving force in eukaryotic evolution.