CAS AN 234 Lecture 3: lecture notes 1:26:17 Evolutionary Theory (cont.) and Adaptation

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Thursday, January 26, 2017
Lecture Notes 1/26/17
Evolutionary Theory pt. 3
-Darwin’s Argument (recap):
-Natural populations could grow exponentially; however, natural populations normally
are relatively stable; therefore, many individuals do not leave as many offspring as
they might; those best suited to the prevailing environment will leave the most
offspring; because of heredity, offspring are like their parents; over many generations,
natural selection builds individuals that are well adapted to their environments
-misconceptions about evolution
-1)survival of the fittest: no, more accurately, reproduction of the fittest, survival is
useful only inasmuch as it leads to successful reproduction
-2)some species are more evolved than others: natural selection required a massive
shift in thinking about our place in nature, no “great chain of being”, everything is
related by descent from a common ancestor, every living thing is equally “evolved”,
organisms evolve traits that aid in survival and reproduction in a specific environment
-however humans are “special”, not in kind but in degree, other primates use tools, but
human tool use is unprecedented, other animals have communication but human
communication is unprecedented, other animals are social, but human sociality is
unprecedented
-3)natural selection is goal directed: selection imparts an advantage to certain
individuals in a particular environment at that particular moment, no “planning” for the
future, whatever traits help an organism survive and reproduce will become more
numerous in the population
-think of natural selection like a tinkerer, not a designer, natural selection works with
existing variation, selecting whichever traits work in the prevailing environment, this
process has been co-opted by engineers to produce innovative designs that would
never have been produced by a human designer
-4)natural selection is a random process: mutations are random, natural selection is
definitively not random, mutation (random changes in the genotype that affect
changes in the phenotype), natural selection (those that pass on their genes are
those that have advantageous traits)
!1
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