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Natural Selection Ch 23, U205PP

Natural Selection Ch 23, U205PP. Natural selection is the primary mechanism of adaptive evolution Natural selection Accumulates and maintains favorable genotypes in a population. Life is not fair…. A Closer Look at Natural Selection. From the range of variations available in a population

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Natural Selection Ch 23, U205PP

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  1. Natural Selection Ch 23, U205PP

  2. Natural selection is the primary mechanism of adaptive evolution • Natural selection • Accumulates and maintains favorable genotypes in a population Life is not fair…

  3. A Closer Look at Natural Selection • From the range of variations available in a population • Natural selection increases the frequencies of certain genotypes, fitting organisms to their environment over generations

  4. Evolutionary Fitness • The phrases “struggle for existence” and “survival of the fittest” • Are commonly used to describe natural selection • Can be misleading • Reproductive success • Is generally more subtle and depends on many factors

  5. Absolute Fitness • is survival and fitness of a particular genotype. • Relative (Darwinian) fitness • Is the contribution of a genotype to the next generation as compared to the contributions of alternative genotypes for the same locus

  6. Why Natural Selection Cannot Fashion Perfect Organisms • Evolution is limited by historical constraints • Adaptations are often compromises • Chance and natural selection interact • Selection can only edit existing variations

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