Download Microevolution is a change in a population*s gene pool

Microevolution is a change in a
population’s gene pool
Ch. 14.4
Populations and Their Gene Pools
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
Population is a local group of individuals
belonging to the same species
Natural selection becomes clear when an
ENTIRE population is tracked over time
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GENE POOL  consists of all the alleles in all
the individuals that make up a population
–
Think of it as the reservoir for the next generation to
gather it’s genes

Where genetic variation is stored
Changes in Gene Pools
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Causes of genetic variation  mutuations and
sexual recombination (random occurrences)
Natural selection is NOT random
–
Environment favors genetic combinations that
CONTRIBUTE to survival/reproductive success

Mendel’s and Darwin’s work combined lead us
to MICROEVOLUTION  a generation to
generation change in the frequencies of alleles
within a population
Genetic Drift
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A change in the gene pool of a population due
to chance  GENETIC DRIFT
ALL populations are subject to genetic drift
–

Smaller pop; more impact genetic drift has on that
pop.
The smaller the sample, the greater the chance
that the results will differ from an expected
result
–
Ex: coin tossed 10 times vs. 1,000 times
Gene Flow and Mutation
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Exchange of genes with another pop.  GENE
FLOW
–
Fertile individuals or their gametes migrate btwn
pops.
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Change in organism’s DNA  MUTATION
Mutations are esp. important as a source of
variation in asexually reproducing organisms
that clone themselves rapidly
Natural Selection and Fitness

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Natural selection is a BLEND of CHANCE and
SORTING
FITNESS  contribution that an individual
makes to the gene pool of the next generation
compared to other individuals