What Is Endosymbiotic Theory?

By Staff WriterLast Updated Mar 30, 2020 11:36:56 AM ET

Endosymbiotic theory holds that chloroplasts and mitochondria came about through the evolution of blue-green algae and bacteria through endocytosis. Endocytosis occurs when a substance passes into a cell through the cell's membrane, and then the cell plasma fuses together to keep the material inside forming an intracellular vesicle.