The origin of eukaryotes

Published on March 31, 2016   29 min

Other Talks in the Series: Evolutionary Physiology

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The title of this lecture is The Origin of Eukaryotes, and I am Neil Blackstone at Northern Illinois University.
Let me briefly review the history of life. This is the history of several major evolutionary transitions. The origin of life, the origin of simple cells, the origin of complex cells that became eukaryotes, and the origin of multicellularity. Much of the complexity of life was built up in this way, first groups of molecules, then molecules within simple cells, simple cells within complex cells and finally complex eukaryotic cells within multicellularity organisms. Note that all complex multicellular organisms are derived from eukaryotic, not prokaryotic, cells.
Each of the major transitions involve lower-level units banding together to form a group. In each case, there was evolutionary conflict among these lower-level units, should they cooperate or should they defect and behave selfishly? For the higher-level unit to emerge, these conflicts had to be mediated. Rick Michod points out that mechanisms of conflict mediation in biology typically decrease the variation of the lower-level units, thus decreasing the likelihood that a selfish lower-level unit will evolve, or increase the variation among the higher-level units, thus increasing the likelihood that a cooperative group will be favored by natural selection.
While evolutionary conflicts impede transitions, other selective forces nevertheless favor banding together. In particular, the resulting groups were larger and tended to be the largest organisms of their time. Because they were bigger, these higher-level units could successfully outcompete any lower-level units that had not banded together. As compared to the smaller lower-level units, higher-level units have a number of ecological advantages such as more food resources, easier dispersal, more offspring, and fewer predators.