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The
title of this lecture
is The Origin of Eukaryotes,
and I am Neil Blackstone
at Northern Illinois University.
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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.
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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.
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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.
