Context:
Mitochondria in eukaryotic cells and chloroplasts in plant cells have evolved from free-living bacteria.
- Present-day cells evolved from a common prokaryotic ancestor along 3 lines of descent, giving rise to archaebacteria, eubacteria, and eukaryotes.
- The endosymbiotic theory explains that the first eukaryotic cells evolved approximately 2 billion years ago.
- Large cells brought about endosymbiosis by engulfing small cells, where the large cells did not digest the small cells. Instead, the small cells lived within the large cells and evolved into organelles.
- From independent cell to organelle the large and small cells formed a symbiotic relationship in which both cells benefited.
- Mitochondria – Some of the small cells were able to break down the large cell’s wastes for energy.
- They supplied energy not only to themselves but also to the large cell.
- They became the mitochondria of eukaryotic cells.
- Chloroplasts – Other small cells were able to use sunlight to make food.
- They shared the food with the large cell.
- They became the chloroplasts of eukaryotic cells.
- The ancestor of mitochondria was a proteobacterium that was engulfed by an asgardarchaean organism.
- Descendants of this endosymbiotic union gave rise to animals, fungi and plants.
- In plants, the intake of a photosynthesizing cyanobacterium followed the asgard-mitochondrial union, and the cyanobacterium became the chloroplasts.
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Evolution of Eukaryotes,Evolution of Eukaryotes
