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)
6. serial engulfment of photosynthetic prokaryotes, which generates
7. ancestral photosynthetic eukaryote with plastids.
Schematic in FFT Article Protist Images: Endosymbiosis and Parasitism Hatena
*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.
More images: Site with good diagrams tems & drop-down menu of endosymbiosis and chloroplasts : diagram of plastid diversity : diagram ~ endosymbiotic formation of algal groups :