Endosymbiosis

• Eukaryotic cells - presence of internal membranes and organelles - lacking in bacteria and archaea. 
• Suggested that to 2 membranes that chloroplasts contain derive from the endosymbiotic procedure itself:
• the inner membrane derives from the prokaryote ancestor.
• the outer membrance derives from the vacuolar membrane of the eukaryotic cell which was involved in engulfing the endosymbiont. 

• Ancestral Eukaryotic cell engulfs an aerobic bacterium (mitochondria).
• It then engulfs a photosynthetic bacterium to form endosymbiosis to form plant cells. 

Evidence

• Mitochondria and chloroplasts are similar in size and morphology to prokaryotes.
• Both reproduce by binary fission as do bacteria.
• Organelles can only arise from pre exsisting organelles.
• Mitochondria and chloroplasts have their own DNA.
• Organellular DNA resembles those of bacteria (DNA phylogeny)
• Organelles contain their own ribosomes.
• Differences in the composition of the 2 membranes.
• Organelles can be targetted by antibiotics specific to prokaryotes.