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General Biology: Evolution of Populations

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  • What evolves in natural selection, individuals or populations?

    Populations evolve over generations, not individuals. Natural selection acts on individuals, but evolutionary change is seen in populations.

  • What is microevolution?

    Microevolution refers to changes in allele frequencies within a population over generations.

  • Name the three mechanisms that can cause changes in allele frequencies.

    Natural selection, genetic drift, and gene flow.

  • Which mechanism leads to adaptive evolution?

    Natural selection is the only mechanism that leads to adaptive evolution.

  • What causes genetic variation among individuals?

    Genetic variation is caused by differences in genes or segments of DNA, combined with environmental influences.

  • What is the difference between discrete and quantitative characters?

    Discrete characters have distinct categories, while quantitative characters vary along a continuum.

  • What is average heterozygosity?

    It measures the percentage of loci at which individuals are heterozygous in a population.

  • What is geographic variation?

    Differences in gene pools of separate populations due to geographic isolation or environmental gradients.

  • How can mutations affect genetic variation?

    Mutations can introduce new alleles by changing nucleotide sequences; they can be neutral, harmful, or beneficial.

  • Why are mutations in somatic cells not passed to offspring?

    Because only mutations in gamete-producing cells can be inherited.

  • How does sexual reproduction contribute to genetic variation?

    By recombining alleles during meiosis, sexual reproduction creates new genetic combinations.

  • What does the Hardy-Weinberg principle state?

    Allele and genotype frequencies in a population remain constant between generations if no evolution occurs.

  • What conditions must be met for Hardy-Weinberg equilibrium?

    No mutations, random mating, no natural selection, large population size, and no gene flow.

  • How do you calculate allele frequencies in a diploid population?

    Count alleles for each genotype, multiply homozygous individuals by 2, add heterozygous alleles, then divide by total alleles.

  • What is the formula representing genotype frequencies in Hardy-Weinberg equilibrium?

    \((p+q)^2 = p^2 + 2pq + q^2\), where p and q are allele frequencies.

  • What is genetic drift?

    Random fluctuations in allele frequencies, especially significant in small populations.

  • What is the founder effect?

    When a small group separates from a larger population, causing different allele frequencies in the new group.

  • What is the bottleneck effect?

    A drastic reduction in population size that changes allele frequencies due to chance survival.

  • How does gene flow affect populations?

    Movement of alleles between populations through migration, which can increase or decrease genetic variation and fitness.

  • What are the three modes of natural selection?

    Directional (favors one extreme), disruptive (favors extremes), and stabilizing (favors intermediate phenotypes).

  • What is sexual selection?

    A form of natural selection that increases mating success, often causing sexual dimorphism.

  • What is heterozygote advantage?

    When heterozygous individuals have higher fitness than either homozygote, maintaining genetic variation.

  • Why can't natural selection produce perfect organisms?

    Because it can only act on existing variation, is limited by historical constraints, and environments constantly change.