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Natural Selection
Darwin’s 4 Main Postulates
1. Individuals, even siblings, in a
population vary (there is variation)
2. These variations can be passed
to offspring (are inherited)
Darwin’s 4 Main Postulates
3. More offspring are produced
than the environment can support,
so there is competition for
resources (from Malthus)
4. Those individuals whose
characteristics make them best
suited to the environment (fitness)
live and reproduce and have more
offspring
(survival of the fittest).
Darwin’s Finches
Individuals do not evolve,
populations evolve!
Evolution is change in the genes of
a population over time.
Both gene frequency (how
common a gene is) and gene
expression (whether it is turned on
or off) can change.
Journal Questions
#2 - If I had a third child and
he/she was born with seven
fingers, would that be an example
of evolution? If so, why? If not
necessarily, what would be
necessary for this to be considered
an example of evolution, and what
factors might influence this?
#3 - Thoughts/Reflections