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1. Gene flow is the movement of alleles (genes) in and out of populations.

KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. Five factors that can lead to evolution. bald eagle migration. 1. Gene flow is the movement of alleles (genes) in and out of populations.

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1. Gene flow is the movement of alleles (genes) in and out of populations.

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

  2. bald eagle migration 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”

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

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

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

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