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•  The origin of eukaryotic cells can be explained by the endosymbiotic theory

An endosymbiont is a cell which lives inside another cell with mutual benefit

Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis

The engulfed prokaryotic cell remained undigested as it contributed new functionality to the engulfing cell (e.g. photosynthesis)

Over generations, the engulfed cell lost some of its independent utility and became a supplemental organelle

Overview of the Process of Endosymbiosis


Evidence for Endosymbiosis

Mitochondria and chloroplasts are both organelles suggested to have arisen via endosymbiosis

Evidence that supports the extracellular origins of these organelles can be seen by looking at certain key features:

  • Membranes (double membrane bound)
  • Antibiotics (susceptibility)
  • Division (mode of replication)
  • DNA (presence and structural composition)
  • Ribosomes (size)

Mnmemonic:  MAD DR  (mad doctor)

Chloroplast and Mitochondrial Evidence

endosymbiosis evidence