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KEY CONCEPT Natural selection is not the only mechanism through which populations evolve.

KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. bald eagle migration. Gene flow is the movement of alleles between populations. Gene flow occurs when individuals join new populations and reproduce. Gene flow keeps neighboring populations similar.

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KEY CONCEPT Natural selection is not the only mechanism through which populations evolve.

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  1. KEY CONCEPT Natural selection is not the only mechanism through which populations evolve.

  2. bald eagle migration Gene flow is the movement of alleles between populations. • Gene flow occurs when individuals join new populations and reproduce. • Gene flow keeps neighboring populations similar. • Low gene flow increases the chance that two populations will evolve into different species.

  3. Genetic drift is a change in allele frequencies due to chance. • Genetic drift causes a loss of genetic diversity. • It is most common in small populations. • A population bottleneck can lead to genetic drift. • It occurs when an eventdrastically reducespopulation size. • The bottleneck effect isgenetic drift that occursafter a bottleneck event. • Leads to lack of genetic genetic variation b/c of the minimized population

  4. It occurs when a few individuals start a new population. • The founder effect is genetic drift that occurs after start of new population. • The founding of a small population can lead to genetic drift.

  5. less likely to have some individuals that can adapt • harmful alleles can become more common due to chance • Genetic drift has negative effects on a population.

  6. Sexual selection occurs when certain traits increase mating success. • Sexual selection occurs due to higher cost of reproduction for females. • males produce many sperm continuously • females are more limited in potential offspring each cycle b/c they produce only 1 egg

  7. intrasexual selection: competition among males • intersexual selection: males • display certain traits to females • There are two types of sexual selection.

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