1. Mechanisms of Evolution
Natural selection
Genetic drift
Sexual selection
Gene flow (migration)
Mutation

2. 1. Genetic Drift RANDOM change in allele frequency
More pronounced in small populations
2 Kinds
Founder effect
Bottleneck effect

3. Founder Effect
A few individuals from a population act as “founders” of a new population
May have only a few of the alleles in original population

4. Bottleneck Effect
Population is reduced to smaller numbers by chance event
Only a few alleles may still remain in gene pool

5. 2. Sexual Selection
Mate choice

6. 3. Gene Flow (Migration)
Add new alleles from other populations

7. 4. Mutation
Only source for brand new alleles for a gene

8. 5. Natural Selection
Organisms with genes that lead to survivorship in certain situations will become more common in a population