Endosymbiotic Theory

Endosymbiosis Symbiosis, which means "living together" is an ecological interaction in which two or more species live in or on each other in close contact. Thus, endosymbiosis is when an organism actually lives within another organism.

The Endosymbiotic Theory The endosymbiotic theory is the idea that a long time ago, prokaryotic cells engulfed other prokaryotic cells by endocytosis. This resulted in the first eukaryotic cells. First proposed by Lynn Margulis Explains the origin of eukaryotic cells Explains the origin of certain membrane-bound organelles

What Exactly Happened? Ancient Prokaryotes Chloroplast Plants and plant-like protists Ancient Prokaryotes Heterotrophic bacteria Nuclear envelope evolving Photosynthetic bacteria Mitochondrion Primitive Autotrophic (Photosynthetic) Eukaryote Animals, fungi, and animal-like protists Ancient Heterotrophic Prokaryote Primitive Heterotrophic Eukaryote

Evidence in support of the endosymbiotic theory: Similarities between mitochondria, chloroplasts, & prokaryotes: Circular DNA Ribosomes Binary fission

Questions Explain the Endosymbiotic Theory. What does “symbiosis” mean? Based on this theory, how did chloroplasts and mitochondria arise?