MasteringBiology Flashcards: Selection
36 Questions
100 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which type of selection tends to increase genetic variation?

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

    • Disruptive selection eliminates phenotypes near the ____ and favors the _____ phenotypes, resulting in ____ in a population.

    average; extreme; increased genetic variation

    In a bell-shaped curve, the x-axis of the graph represents which of the following?

  • Frequency of traits
  • The value of a particular characteristic (correct)
  • The average of the traits
  • None of the above

    • Heterozygote advantage leads to less genetic variation in the population.

    <p>False</p> Signup and view all the answers

    Which kind of selection appears to have made giraffes long-necked?

    <p>Directional selection</p> Signup and view all the answers

    Directional selection drives the average of the population _____

    <p>in one direction</p> Signup and view all the answers

    Which kind of selection is most likely at work regarding the birth weight of babies?

    <p>Stabilizing selection</p> Signup and view all the answers

    Stabilizing selection causes _____; ____ phenotypes become less common.

    <p>no change in the average of the population; extreme</p> Signup and view all the answers

    Which kind of selection acts on beak size in black-bellied seedcrackers?

    <p>Disruptive selection</p> Signup and view all the answers

    Disruptive selection causes ____ to be favored over the intermediate phenotypes.

    <p>both extreme phenotypes</p> Signup and view all the answers

    Which kind of selection acts on the adult body size of Aristelliger lizards?

    <p>Stabilizing selection</p> Signup and view all the answers

    Allele frequencies measure _____

    <p>the relative proportions of different alleles in a population</p> Signup and view all the answers

    By looking at how allele frequencies change over time, ____

    <p>you can see how populations are evolving</p> Signup and view all the answers

    Consistently causes a population to become better adapted to its environment

    <p>Natural selection</p> Signup and view all the answers

    Cannot cause a harmful allele to become more common

    <p>Natural selection</p> Signup and view all the answers

    A result of differential success in reproduction

    <p>Natural selection</p> Signup and view all the answers

    Responsible for the founder effect

    <p>Genetic drift</p> Signup and view all the answers

    Causes allele frequencies to fluctuate randomly

    <p>Genetic drift</p> Signup and view all the answers

    Responsible for the bottleneck effect

    <p>Genetic drift</p> Signup and view all the answers

    A result of the movement of fertile individuals or their gametes

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

    Can introduce new alleles into a population's gene pool

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

    Natural selection is the result of ____

    <p>differential survival and reproduction</p> Signup and view all the answers

    Natural selection is the only mechanism of evolution that ____

    <p>consistently causes a population to become better adapted to its environment</p> Signup and view all the answers

    Genetic drift describes evolution due to _____ and causes _____ fluctuations in allele frequencies.

    <p>chance events; unpredictable</p> Signup and view all the answers

    Genetic drift can have a _____ effect in a small population

    <p>particularly significant</p> Signup and view all the answers

    Gene flow results when _____.

    <p>alleles are transferred into or out of a population due to the migration of fertile individuals or their gametes</p> Signup and view all the answers

    Gene flow can bring new alleles that are ____, ____, or ___ into a population

    <p>beneficial, harmful, or neutral</p> Signup and view all the answers

    During an extreme heat wave, plants with white flowers survive better. Mechanism? Effect on allele frequencies?

    <p>Natural selection; frequency of white allele increases</p> Signup and view all the answers

    A person uproots the five closest plants, which all happen to have white flowers. Mechanism? Effect on allele frequencies?

    <p>Genetic drift; frequency of purple allele increases</p> Signup and view all the answers

    A storm kills many plants at random. Mechanism? Effect on allele frequencies?

    <p>Genetic drift; allele frequencies change but not predictably</p> Signup and view all the answers

    Plants with purple flowers attract more insects, which pollinate the plants. Mechanism? Effect on allele frequencies?

    <p>Natural selection; frequency of purple allele increases</p> Signup and view all the answers

    Workers from a nearby greenhouse accidentally introduce white flower seeds into this population's habitat. Mechanism? Effect on allele frequencies?

    <p>Gene flow; frequency of white allele increases</p> Signup and view all the answers

    Different events and conditions result in _____, _____, and ____

    <p>natural selection, genetic drift, and gene flow</p> Signup and view all the answers

    Natural selection, genetic drift, and gene flow cause _____ in different ways

    <p>allele frequencies to change and populations to evolve</p> Signup and view all the answers

    _____, which results from differential survival and reproduction, is the only mechanism of evolution that consistently causes a population to become better adapted to its environment.

    <p>Natural selection</p> Signup and view all the answers

    _____ and _____ cause alleles to increase in frequency regardless of whether they are harmful, neutral, or beneficial, _____ causes only beneficial alleles to become more common in a population.

    <p>Genetic drift; gene flow; natural selection</p> Signup and view all the answers

    Study Notes

    Selection Types and Genetic Variation

    • Disruptive selection increases genetic variation by favoring extreme phenotypes while eliminating average ones.
    • Directional selection alters the average phenotype in a population by pushing it in a specified direction, as seen in giraffes with long necks.
    • Stabilizing selection maintains the average phenotype while reducing the frequency of extreme phenotypes, such as birth weights leading to complications with very large or small babies.

    Phenotype Influence and Traits

    • In bell-shaped curves, the x-axis represents the range of a specific characteristic, such as size or color.
    • Black-bellied seedcrackers exhibit disruptive selection in beak size, as they have adapted to eat either soft or hard seeds.

    Genetic Concepts

    • Heterozygote advantage provides better fitness for heterozygous individuals, resulting in increased genetic variation contrary to the notion that it reduces variation.
    • Allele frequencies indicate the proportion of different alleles within a population, essential for studying evolution over time.

    Evolutionary Mechanisms

    • Natural selection is driven by differential survival and reproduction, consistently enhancing a population's adaptation to its environment.
    • Genetic drift randomly affects allele frequencies, causing significant effects in small populations due to chance events.
    • Gene flow introduces new alleles into a population, which can be beneficial, harmful, or neutral, affecting genetic diversity.

    Mechanisms and Allele Frequency Changes

    • During natural selection, plants with advantageous traits (e.g., white flowers during a heat wave) have allele frequencies that increase in their favor.
    • Genetic drift can lead to increased frequencies of specific alleles through chance events, such as uprooting plants or random storms affecting populations unpredictably.
    • Different events, like purposeful removal of plants or accidental introductions of seeds, demonstrate how genetic drift and gene flow can unpredictably change allele frequencies.

    Summarizing Change in Evolution

    • Natural selection, genetic drift, and gene flow are mechanisms that contribute to changes in allele frequencies and population evolution in distinct ways.
    • Only natural selection effectively leads to adaptation, while genetic drift and gene flow may increase allele frequencies without consideration of their effects on fitness.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz focuses on concepts related to selection in genetics, particularly disruptive selection. Test your understanding of how this type of selection influences genetic variation and its representation on graphs. Ideal for biology students wishing to master these concepts.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser