Biology 2581B Lecture Notes - Lecture 3: Proteobacteria, Archaea, Eukaryote
28 Apr 2016
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Document Summary
Endosymbiosis begins with 2 distinct organisms, both free-living and unicellular and both with a distinct genome. One of the organisms then engulfs the other, but digestion for some reason does not occur. The engulfed organism stays inside the host, and sometimes a benefit (one way or the other) can occur. Over time, the host and the endosymbiont share molecules (e. g. macromolecules). Eventually, this sharing relationship develops deep enough to be called an endosymbiotic relationship. Later on, due to random mutations, a certain gene that allows the endosymbiont to be free- living is lost. As a result, the endosymbiont is trapped inside the host as it cannot live outside the host anymore: by losing a gene that allows the endosymbiont to be free living, it turns the evolutionary ratchet. The evolutionary ratchet is turned by events which are very hard to undo once they have occurred as it increases the complexity between the two interacting systems.
