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Transcript
Mechanisms of
Evolution
Gene Pool
• All the genes
present in a
population
Genetic Drift
• Evolution occurring through random
changes in allele frequency over time.
Genetic Drift
• Creation of gametes
is randomized
• Some alleles are
passed on more than
others by chance
http://www.biology.arizona.edu/evolution/act/drift/frame.html
• Gene drift is more noticeable in smaller
populations. Why?
Types of Genetic Drift
• Founder Effect: occurs when a small
group of individuals colonize a new habitat
• allele frequency changes as a result of the
migration of a small subgroup
Types of Genetic Drift
• Bottleneck effect: a significant percent of
the population is killed or cannot
reproduce
– Natural disaster
– Habitat destruction
– Hunting
Bottleneck Effect
Gene Flow
• Movement of genes from one population
to another
Divergent Evolution
• Differences between
groups can lead to the
formation of new species
• different groups adapt to
different environments
• Remember homologous
structures
Ancestral Cat
Convergent Evolution
• Different organisms living in
similar environments can
evolve similar traits
• Convergent Evolution: the
process by which unrelated
organisms come to resemble
each other
• Remember analogous
structures!
– Shark and dolphin