BIO130H1 Chapter Notes - Chapter 1: Alphaproteobacteria, Proteobacteria, Endomembrane System
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BIO130H1 Full Course Notes
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Document Summary
The next step in the evolution of modern eukaryotes was when a descendent of the feca cell ingested a small, aerobic prokaryote which somehow resisted digestion within the cytoplasm, taking up residence as a permanent endosymbiont. As the host cell reproduced, so did the endosymbiont, so that a colony of these composite cells was soon produced. Over many generations, endosymbionts lost many of the traits that were no longer required for survival, and the once independent oxygen respiring microbes evolved into precursors of modern day mitochondria. Researchers have compared the dna sequences of mitochondrial genes (mtdna) with those found in major clades of bacteria and archaea. Collectively, such studies indicate that mitochondria arose from an alpha proteobacterium. Margulis proposed that the acquisition of another endosymbiont cell, more specifically a cyanobacteria, had converted an early heterotrophic eukaryote into an ancestor of photosynthetic eukaryotes: the green algae and plants.
