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Published byReynard Cross Modified over 9 years ago
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KEY CONCEPT Natural selection is not the only mechanism through which populations evolve. Five factors that can lead to evolution.
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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
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Gene flow moves alleles from one population to another.
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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.
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Example 2: Founder Effect
Few individuals colonize a new population Occurs after start of new population.
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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
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3. Mutations produce the genetic variation needed for evolution.
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4. Sexual selection selects for traits that improve mating success.
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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
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Two Types intrasexual selection: competition among males intersexual selection: males display certain traits to females
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5. Natural selection selects for traits advantageous for survival.
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