How do organelles, bacteria, and protists factor into the Endosymbiotic theory?
Original hypothesis: * mitochondria are the result of endocytosis of aerobic bacteria * chloroplasts are the result of endocytosis of photosynthetic bacteria * (the two above) by large anaerobic bacteria that would not otherwise be able to exist in an aerobic environment. * this arrangement became a mutually beneficial relationship for both cells (symbiotic relationship). Scientists think that mitochondria and chloroplasts were once free-living because * mitochondria and chloroplasts are the same size as prokaryotic cells * they divide by binary fission * mitochondria and chloroplasts have their own DNA & their own ribosomes Lynn Margulis theorized: IF mitochondria and chloroplasts truly were engulfed bacterial endosymbiotes, THEN there would be evidence of bacterial DNA within those organelles. (Later verified.) The endosymbiotic theory does not prove that mitochondria and chloroplasts are direct descendants of bacteria.
