1. ancestral prokaryote, undergoes
2. infoldings of plasma membrane, which permits
3. development of nuclear membrane and endomembranous system
4. engulfment of aerobic heterotrophic prokaryotes, generates
5. ancestral heterotrophic eukaryote with mitochondria.
Next, acccording to SET,
an ancestral heterotropic eukaryote (5) undergoes
6. serial engulfment of photosynthetic prokaryotes, which generates
7. ancestral photosynthetic eukaryote with plastids.
*Secondary endosymbiosis is engulfment by a eukaryotic cell of another eukaryote that already possesses endosymbiotic organelles derived from primary endosymbiosis. Similarly, acquisitions may be tertiary. The eukaryotic crown group Alveolata has a particularly complex history of plastid acquisition.