Biology 2581B Lecture Notes - Lecture 3: Symbiosis, Lokiarchaeota, Archaea
28 Jan 2016
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Hypothetical example: two organisms (distinct a and b) Unicellular and have a genome; a feeds on b. B stays in undigested somehow inside of a. B could be parasitic, but here imagined as mutually beneficial. B learns how to stay undigested, starts to adapt to insides of a, etc. ) Can start calling a the host and b the symbiont (maintained throughout the life cycle or long periods of time) B can still subsist on its own w/o a; genes may allow for this (gene x) After a random mutation b can no longer live freely (endosymbiotic gene loss); b can now only be okay within organism a. B is now trapped inside a; no going back. Like an evolutionary ratchet (genetic evolutionary change that increases complexity, resulting in the organism being forced to evolve in one direction) B now trapped has less genetic function devoted to survival (loses unnecessary genetic machinery and gains adaptations needed for function within.
