Download AP Biology Natural selection acts on individuals “survival of the fittest”

Evolution of Populations
 Natural selection acts on individuals
 “survival of the fittest”

differential reproductive success
 who bears more offspring
 Populations evolve

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genetic makeup (alleles in gene
pool) of population changes
over time
Mummichog
Individuals survive or don’t survive…
Individuals DON’T evolve…
Individuals are selected
Populations evolve
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2007-2008
5 Agents of evolutionary change
Mutation
Gene Flow
Genetic Drift
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Non-random mating
Selection
Where does Genetic Variation come from?

random changes to DNA
Wet year
Beak depth
 Mutation
Dry year
Dry year
Dry year
 errors in mitosis & meiosis
1977
 environmental damage
 recombination of alleles
 new arrangements in every offspring
 new combinations = new
phenotypes
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1982
1984
11
Beak depth of
offspring (mm)
 Gene Shuffling
1980
10
9
8
Medium ground finch
8
9
10
11
Mean beak depth of parents (mm)
1. Mutation & Variation
 Mutation changes DNA sequence
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2. Gene Flow
 Movement of individuals &
alleles in & out of populations
seed & pollen distribution by
wind & insect
 migration of animals

 causes genetic mixing
across regions
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3. Non-random mating
 Sexual selection
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4. Genetic drift
 Effect of chance events

founder effect
 small group splinters off & starts a new colony

bottleneck
 some factor (disaster) reduces population to
small number & then population recovers &
expands again
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5. Natural selection
 Differential survival & reproduction due
to changing environmental conditions
AP Biology
5 Agents of evolutionary change
Mutation
Gene Flow
Genetic Drift
AP Biology
Non-random mating
Selection