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

Explore the key concepts of gene flow, genetic drift, and sexual selection in population evolution. Understand how gene flow leads to similarity between neighboring populations while genetic drift can cause loss of genetic diversity. Discover how sexual selection influences mating success through competition and display of traits.

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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 Definition: Gene flow is the movement of alleles between populations. • How it works: Gene flow occurs when individuals join new populations and reproduce. • Lots of Gene flow results in neighboring populations that are similar. • Limited gene flow results in the chance that two populations will evolve into different species.

  3. Definition: Genetic drift is a change in allele frequencies due to chance or catastrophe. • How it works: Causes a loss of genetic diversity. In small populations. • A bottleneck effect: • It occurs when an eventdrastically reducespopulation size.

  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. Definition: Sexual selection occurs when certain traits increase mating success. • How it works: • males produce many sperm continuously; females have fewer eggs

  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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