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Genes, Chromosomes, etc. The tiny mechanisms of evolution. This slide intentionally left. blank. Evolution at the Population Level. Gene Flow. The Movement of Alleles The Movement of Alleles Migration and Inter-breeding. Genetic Drift. Random change in gene pool, - PowerPoint PPT Presentation
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Genes, Chromosomes, etc.
The tiny mechanisms of evolution
This slide intentionally left
blank
Evolution at the Population Level
Gene Flow The Movement of Alleles
The Movement of AllelesMigration and Inter-breeding
Genetic Drift Random change in gene pool,
particularly powerful in small populations
Genetic Drift
Genetic Drift and Population Size
Founder Effect Small number of individuals from population
migrate and form new population May not carry all alleles in parent population May carry alleles in different frequencies
from parent population
Bottleneck Effect Catastrophic events (floods, diseases)
leave a few survivors Survivors may not carry all alleles in
parent population May carry alleles in different
frequencies from parent population
The Bottleneck Effect
Forces of Evolution and Genetic Variation
Evolutionary Force
Variation within population
Variation between populations
Mutation Increases Increases
Gene Flow Increases Decreases
Genetic Drift Decreases Increases
Natural Selection
Decreases or stabilizes
Increases
Speciation and Forces of Evolution Time
› Mutation and natural selection produce change over time
› Enough time (and change) leads to appearance of new “kind”
Reproductive isolation› No gene flow to reduce differences
between populations› Mutations, genetic drift, and natural
selection increase differences