Symbiogenesis
Theory that eukaryotic cells arose from symbiotic mergers of prokaryotes.
Symbiogenesis, also known as the endosymbiotic theory or serial endosymbiotic theory, is the leading evolutionary theory for the origin of eukaryotic cells from prokaryotic organisms. It holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes taken one inside the other in endosymbiosis.
- field
- Evolutionary biology, cell biology
- key_proponents
- Konstantin Mereschkowski, Lynn Margulis
- core_claim
- Mitochondria and plastids originated from endosymbiotic bacteria
- current_status
- Widely accepted for mitochondria and chloroplasts
Lore & Background
Mereschkowski proposed that complex life-forms originated by two episodes of symbiogenesis: the incorporation of symbiotic bacteria to form nuclei and chloroplasts. Essay on the Theory of Symbiogenesis, writing, 'The theory of symbiogenesis is a theory of selection relying on the phenomenon of symbiosis.'
Reader's Guide
Symbiogenesis revolutionized the history of evolution by proposing a mechanism for evolutionary development not encompassed in the original Darwinian vision. It demonstrated that major evolutionary advancements, particularly the origin of eukaryotic cells, may have resulted from symbiotic mergers rather than from gradual mutations and individual competition—that is, classical natural selection. Accordingly, symbiogenic theory suggests that endosymbiosis may be a powerful force in generating evolutionary novelty, beyond that which can be explained by natural selection alone. The fundamental theory of symbiogenesis as the origin of mitochondria and chloroplasts is now widely accepted.
Did You Know?
- Mitochondria appear to be phylogenetically related to Rickettsiales bacteria, while chloroplasts are thought to be related to cyanobacteria.
- The transport proteins called porins are found in the outer membranes of mitochondria and chloroplasts, and also bacterial cell membranes.
- Cardiolipin is found only in the inner mitochondrial membrane and bacterial cell membranes.
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