Evolution and Population Genetics
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What is the primary role of natural selection in a population?

  • It favors phenotypes that are less adapted to the environment.
  • It decreases genetic variation within a population.
  • It has no impact on the reproductive success of organisms.
  • It increases the frequencies of certain genotypes over generations. (correct)

    • Which term best describes the contribution of one genotype relative to others for a specific trait?

  • Absolute fitness
  • Phenotypic relevance
  • Relative fitness (correct)
  • Genetic drift

    • What type of selection favors individuals at both extremes of the phenotypic range?

  • Stabilizing selection
  • Directional selection
  • Disruptive selection (correct)
  • Sexual selection

    • What is a common misconception about evolutionary fitness?

    <p>It encompasses a variety of subtle factors influencing reproductive success.</p> Signup and view all the answers

    Which of the following terms refers to the struggle for existence within natural selection?

    <p>Survival of the fittest</p> Signup and view all the answers

    What is microevolution primarily concerned with?

    <p>Change in the genetic makeup of a population.</p> Signup and view all the answers

    Which of the following processes is NOT a main evolutionary process affecting allele frequency?

    <p>Gene cloning</p> Signup and view all the answers

    Which statement best describes the concept of a gene pool?

    <p>The collection of all genes and their variants in a population.</p> Signup and view all the answers

    What does population genetics study?

    <p>The genetic changes in populations over time.</p> Signup and view all the answers

    Which of the following characterizes the Modern Synthesis in evolutionary biology?

    <p>It reconciles Mendelian genetics with Darwinian evolution.</p> Signup and view all the answers

    What is a population in the context of evolution?

    <p>A localized group capable of interbreeding.</p> Signup and view all the answers

    Which factor is least likely to contribute to the evolution of a population?

    <p>Organism's personal fitness.</p> Signup and view all the answers

    What does the study of allele frequency changes in populations help scientists understand?

    <p>The mechanisms of microevolution.</p> Signup and view all the answers

    Which process is primarily responsible for creating genetic variation in sexually reproducing populations?

    <p>Sexual recombination</p> Signup and view all the answers

    What is a characteristic of point mutations?

    <p>They can significantly impact phenotype despite being a change in one base.</p> Signup and view all the answers

    Which of the following is true regarding mutation rates in organisms?

    <p>They tend to be lower in animals and plants as compared to microorganisms.</p> Signup and view all the answers

    What is genetic drift primarily influenced by?

    <p>The size of the population</p> Signup and view all the answers

    How do chromosomal mutations typically affect an organism?

    <p>They are almost always harmful.</p> Signup and view all the answers

    What results from natural selection in a population?

    <p>Some alleles are passed on at greater frequencies.</p> Signup and view all the answers

    Which of the following statements about mutation is incorrect?

    <p>Most mutations are beneficial and lead to improved fitness.</p> Signup and view all the answers

    What role does gene flow play in microevolution?

    <p>It introduces new alleles from other populations.</p> Signup and view all the answers

    What is the role of diploidy in the preservation of genetic variation?

    <p>It maintains genetic variation through hidden recessive alleles.</p> Signup and view all the answers

    Which mechanism exemplifies balancing selection?

    <p>Maintaining stable frequencies of two or more phenotypic forms.</p> Signup and view all the answers

    What advantage do heterozygous individuals have at certain loci?

    <p>Greater fitness than homozygotes.</p> Signup and view all the answers

    How does the sickle-cell allele demonstrate heterozygote advantage?

    <p>It confers resistance to malaria while causing mutations.</p> Signup and view all the answers

    What occurs during frequency-dependent selection?

    <p>Fitness declines for morphs that become too common in the population.</p> Signup and view all the answers

    What is a potential outcome of balancing selection?

    <p>Maintenance of multiple alleles at frequencies.</p> Signup and view all the answers

    Which factor contributes most to maintaining genetic variation in populations?

    <p>Frequent migrations leading to new alleles.</p> Signup and view all the answers

    What is the consequence of heterozygote advantage for alleles at particular loci?

    <p>It leads to the preservation of both alleles.</p> Signup and view all the answers

    What does the gene pool represent in a population?

    <p>The total aggregate of genes at any one time</p> Signup and view all the answers

    What does the Hardy-Weinberg theorem state about allele frequencies?

    <p>They remain constant unless outside forces act</p> Signup and view all the answers

    In a population at Hardy-Weinberg equilibrium, what is the expected frequency of the homozygous genotype represented by p²?

    <p>64%</p> Signup and view all the answers

    If the allele frequency of allele A is represented by p and allele a by q, which equation holds true?

    <p>p + q = 1</p> Signup and view all the answers

    Under what condition will allele frequencies not change within a population?

    <p>When gametes contribute randomly to the next generation</p> Signup and view all the answers

    What is the frequency of the heterozygous genotype in a population, defined by the formula 2pq?

    <p>2pq</p> Signup and view all the answers

    Which of the following is a condition for a population to be in Hardy-Weinberg equilibrium?

    <p>Random mating must occur</p> Signup and view all the answers

    What effect do real-world conditions have on allele and genotype frequencies in populations over time?

    <p>They change over time</p> Signup and view all the answers

    What percentage of the population in Hardy-Weinberg equilibrium with allele frequencies p = 0.8 and q = 0.2 will be homozygous recessive?

    <p>4%</p> Signup and view all the answers

    Which statement is true regarding the Hardy-Weinberg theorem?

    <p>It is based on specific genetic principles</p> Signup and view all the answers

    Study Notes

    Overview

    • Evolution occurs in populations, not individuals.
    • Natural selection acts on individuals.

    Genetic Variation

    • Genetic variations in populations contribute to evolution.

    Population Genetics

    • Microevolution is the change in the genetic makeup of a population over generations.
    • Population genetics studies these changes.

    The Modern Synthesis

    • Reconciled Darwin’s and Mendel’s ideas.
    • Integrates Mendelian genetics with Darwinian theory of evolution by natural selection.
    • Focuses on populations as the unit of evolution.

    Gene Pools and Allele Frequencies

    • A population is a localized group of individuals capable of interbreeding and producing fertile offspring.
    • Gene pool is the total aggregate of genes in a population at any given time.
    • Gene pool consists of all gene loci in all individuals of the population.

    The Hardy-Weinberg Theorem

    • Describes a population that is not evolving.
    • Allele and genotype frequencies remain constant from generation to generation provided that only Mendelian segregation and recombination of alleles are at work.

    Hardy-Weinberg Equilibrium

    • Describes a population where random mating occurs.
    • Allele frequencies do not change.

    Conditions for Hardy-Weinberg Equilibrium

    • The Hardy-Weinberg theorem describes a hypothetical population.
    • Real populations have changing allele and genotype frequencies.

    Causes of Microevolution

    • Mutation and sexual recombination produce variation that makes evolution possible.

    Mutation

    • Changes in the nucleotide sequence of DNA.
    • Creates new genes and alleles.

    Point Mutations

    • A change in one base in a gene.
    • Can have a significant impact on phenotype.
    • Usually harmless, but may have an adaptive impact.

    Mutations That Alter Gene Number or Sequence

    • Chromosomal mutations are almost certain to be harmful.
    • May be neutral or even beneficial.
    • Gene duplication can duplicate chromosome segments.

    Mutation Rates

    • Mutation rates are typically low in animals and plants.
    • Rates are more rapid in microorganisms.

    Sexual Recombination

    • Important for producing genetic differences that enable adaptation.
    • Far more important than mutation in sexually reproducing populations.

    Natural Selection

    • Differential success in reproduction.
    • Results in particular alleles being passed on to the next generation in greater proportions.

    Genetic Drift

    • Change in allele frequencies due to random chance.
    • A smaller sample size increases the chance of deviation from the expected result.

    Natural Selection

    • Increases the frequency of genotypes that are better suited to the environment.

    Evolutionary Fitness

    • An organism’s contribution to the gene pool of the next generation, relative to other individuals.

      Relative Fitness

      • The contribution of a genotype to the next generation relative to alternative genotypes for the same locus.

    Modes of Selection

    • Natural selection can favor certain genotypes, leading to three modes of selection:
    • Directional Selection
    • Disruptive Selection
    • Stabilizing Selection

    Directional Selection

    • Favors individuals at one end of the phenotypic range.
    • Examples: peppered moths, giraffe necks, long lizard tails, etc.

    Disruptive Selection

    • Favors individuals at both extremes of the phenotypic range.
    • Creates a bimodal distribution.

    Preservation of Genetic Variation

    • Mechanisms help to preserve genetic variation in a population.
    • Diploidy
    • Balancing Selection

    Diploidy

    • Maintains genetic variation through recessive alleles.

    Balancing Selection

    • Maintains stable frequencies of two or more phenotypic forms in a population.
    • Leads to a state called balanced polymorphism.

    Heterozygote Advantage

    • Heterozygotes have greater fitness than homozygotes.
    • Example: sickle-cell allele.

    Frequency-Dependent Selection

    • The fitness of any morph declines if it becomes too common in the population.

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    Lecture 3 - Population Genetics 2 PDF

    Description

    Test your knowledge on the principles of evolution and population genetics. This quiz covers topics such as natural selection, genetic variation, and the Hardy-Weinberg theorem, providing a comprehensive overview of how populations evolve over time. Challenge yourself and see how well you understand these fundamental concepts.

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