AP Biology evolution unit covering natural selection, population genetics, Hardy-Weinberg equilibrium, and evidence for evolution.
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- What is natural selection?
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The process where organisms with advantageous heritable traits are more likely to survive and reproduce, passing those traits to offspring.- What three components must be present for natural selection to occur?
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Variation in the population, heritable traits, and differential reproductive success.- What is directional selection?
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Natural selection that favors one extreme phenotype, causing the population average to shift toward that extreme.- What is stabilizing selection?
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Natural selection that favors the intermediate phenotype, reducing variation and maintaining the population mean.- What is disruptive selection?
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Natural selection that favors both extreme phenotypes over the intermediate, increasing variation.- Explain the peppered moth example of natural selection.
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Light moths were camouflaged on light bark, dark moths on dark bark. Industrial pollution darkened bark, so dark moths became more common, then declined when pollution decreased.- What is an adaptation?
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A heritable trait that increases an organism's fitness in a particular environment.- What is heritable variation?
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Differences in traits among individuals in a population that are caused by genetic differences, not environment.- Why is variation necessary for natural selection to act?
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Without variation in traits, all individuals have equal chances of survival and reproduction, so selection cannot favor certain alleles.- What did Darwin observe about finch beaks on the Galapagos Islands?
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Different finch species had different beak sizes and shapes, each adapted to the available food sources on their island.- What is allele frequency?
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The proportion of a particular allele among all alleles at a locus in a population.- What is genotype frequency?
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The proportion of a particular genotype among all individuals in a population.- What is Hardy-Weinberg equilibrium?
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A stable state where allele and genotype frequencies do not change from generation to generation.- State the Hardy-Weinberg equation.
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p squared plus 2pq plus q squared equals 1, where p and q are allele frequencies.- In the Hardy-Weinberg equation, what does p squared represent?
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The frequency of the homozygous dominant genotype.
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