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Evolution and Natural
Natural Selection does not produce
perfection, just “good enough”.
 Natural selection is not all-powerful; it
does not produce perfection
 If your genes are “good enough,” you’ll
get some offspring into the next
generation—you don’t have to be perfect
Natural Selection has no goals; it’s
not striving to produce “progress”
or a balanced ecosystem
Natural selection is a process rather than a
guiding hand
Natural selection is the simple result of
variation, differential reproduction, and
It is mindless and mechanistic. It has no
goals; it’s not striving to produce “progress”
or a balanced ecosystem.
Natural Selection is a random
 The genetic variation that occurs in a
population because of mutation is random
 Selection acts on that variation in a very
non-random way: genetic variants that
aid survival and reproduction are much
more likely to become common than
variants that don't
Evolutionary theory implies that
life evolved (and continues to
evolve) randomly, or by chance
Chance and randomness do factor into
Important mechanisms of evolution are nonrandom and these make the overall process
non-random --- selection
Process of mutation, which generates genetic
variation, is random, but selection is nonrandom
Evolution results in progress;
organisms are always getting
better through evolution
 Natural selection does result in the
evolution of improved abilities to survive
and reproduce
 Mutation, migration, and genetic drift may
cause populations to evolve in ways that
are actually harmful overall or make them
less suitable for their environments
 Evolution produces a tree, not a ladder
Individual organisms can evolve
during a single lifespan
 Populations, not individual organisms,
 Evolutionary change is based on changes
in the genetic makeup of populations over
Evolution only occurs slowly and
Evolution occurs slowly and gradually, but
it can also occur rapidly
 Over the past 50 years, we've observed
squirrels evolve new breeding times in
response to climate change, a fish species
evolve resistance to toxins dumped into
the Hudson River, and a host of microbes
evolve resistance to new drugs we've
Because evolution is slow,
humans cannot influence it
 Humans often cause major changes in the
environment, we are frequently the
instigators of evolution in other
 Pesticide and bacterial resistence
Genetic drift only occurs in
small populations
Genetic drift has a larger effect on small
populations, but the process occurs in all
Genetic drift occurs because, due to chance,
the individuals that reproduce may not
exactly represent the genetic makeup of the
whole population
In large populations, the changes in gene
frequency from generation to generation tend
to be small, while in smaller populations,
those shifts may be much larger