11.3 Other Mechanisms of Evolution
KEY CONCEPT
Natural selection is not the only mechanism through which populations evolve.
Five factors that can lead to evolution.

11.3 Other Mechanisms of Evolution
1. Gene flow is the movement of alleles (genes) in and out of populations.
occurs when individuals join new populations and reproduce-migrate
Increase genetic variation in the receiving population
Animal move
Plants and fungi-wind,
“hitchhikers” bald eagle migration

11.3 Other Mechanisms of Evolution
• Gene flow moves alleles from one population to another.

11.3 Other Mechanisms of Evolution
2. Genetic drift is a random change in allele frequencies due to chance.
Causes a LOSS of genetic diversity in a population.
More common in small populations
Example1: Bottleneck Effectnatural or man-made disaster leads to a drastic reduction in population size.

11.3 Other Mechanisms of Evolution
Example 2: Founder Effect
Few individuals colonize a new population
Occurs after start of new population.

11.3 Other Mechanisms of Evolution
Negative Effects on a Population.
Less likely to have some individuals that can adapt
Harmful alleles can become more common due to chance
Reduces variation and adaptability

11.3 Other Mechanisms of Evolution
3. Mutations produce the genetic variation needed for evolution.

11.3 Other Mechanisms of Evolution
4. Sexual selection selects for traits that improve mating success.

11.3 Other Mechanisms of Evolution
3. Non-random mating-Sexual selection occurs when certain traits increase mating success.
– males produce many sperm continuously
– females are more limited in potential offspring each cycle

11.3 Other Mechanisms of Evolution
• Two Types
– intrasexual selection: competition among males
– intersexual selection: males display certain traits to females

11.3 Other Mechanisms of Evolution
5. Natural selection selects for traits advantageous for survival.