1. KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. Five factors that can lead to evolution.

2. occurs when individuals join new populations and reproduce-migrate
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

3. Gene flow moves alleles from one population to another.

4. 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 Effect- natural or man-made disaster leads to a
drastic reduction in population size.

5. Example 2: Founder Effect
Few individuals colonize a new population
Occurs after start of new population.

6. 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

7. 3. Mutations produce the genetic variation needed for evolution.

8. 4. Sexual selection selects for traits that improve mating success.

9. 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

10. Two Types
intrasexual selection: competition among males
intersexual selection: males display certain traits to females

11. 5. Natural selection selects for traits advantageous for survival.