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