MasteringBiology Flashcards: Selection

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.

False Signup and view all the answers

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

Directional selection Signup and view all the answers

Directional selection drives the average of the population _____

in one direction Signup and view all the answers

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

Stabilizing selection Signup and view all the answers

Stabilizing selection causes _; phenotypes become less common.

no change in the average of the population; extreme Signup and view all the answers

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

Disruptive selection Signup and view all the answers

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

both extreme phenotypes Signup and view all the answers

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

Stabilizing selection Signup and view all the answers

Allele frequencies measure _____

the relative proportions of different alleles in a population Signup and view all the answers

By looking at how allele frequencies change over time, ____

you can see how populations are evolving Signup and view all the answers

Consistently causes a population to become better adapted to its environment

Natural selection Signup and view all the answers

Cannot cause a harmful allele to become more common

Natural selection Signup and view all the answers

A result of differential success in reproduction

Natural selection Signup and view all the answers

Responsible for the founder effect

Genetic drift Signup and view all the answers

Causes allele frequencies to fluctuate randomly

Genetic drift Signup and view all the answers

Responsible for the bottleneck effect

Genetic drift Signup and view all the answers

A result of the movement of fertile individuals or their gametes

Gene flow Signup and view all the answers

Can introduce new alleles into a population's gene pool

Gene flow Signup and view all the answers

Natural selection is the result of ____

differential survival and reproduction Signup and view all the answers

Natural selection is the only mechanism of evolution that ____

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

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

chance events; unpredictable Signup and view all the answers

Genetic drift can have a _____ effect in a small population

particularly significant Signup and view all the answers

Gene flow results when _____.

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

Gene flow can bring new alleles that are __, , or _ into a population

beneficial, harmful, or neutral Signup and view all the answers

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

Natural selection; frequency of white allele increases 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?

Genetic drift; frequency of purple allele increases Signup and view all the answers

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

Genetic drift; allele frequencies change but not predictably Signup and view all the answers

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

Natural selection; frequency of purple allele increases 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?

Gene flow; frequency of white allele increases Signup and view all the answers

Different events and conditions result in ___, _, and __

natural selection, genetic drift, and gene flow Signup and view all the answers

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

allele frequencies to change and populations to evolve 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.

Natural selection 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.

Genetic drift; gene flow; natural selection 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.

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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.

MasteringBiology Flashcards: Selection

Questions and Answers

Which type of selection tends to increase genetic variation?

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

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

Heterozygote advantage leads to less genetic variation in the population.

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

Directional selection drives the average of the population _____

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

Stabilizing selection causes _____; ____ phenotypes become less common.

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

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

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

Allele frequencies measure _____

By looking at how allele frequencies change over time, ____

Consistently causes a population to become better adapted to its environment

Cannot cause a harmful allele to become more common

A result of differential success in reproduction

Responsible for the founder effect

Causes allele frequencies to fluctuate randomly

Responsible for the bottleneck effect

A result of the movement of fertile individuals or their gametes

Can introduce new alleles into a population's gene pool

Natural selection is the result of ____

Natural selection is the only mechanism of evolution that ____

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

Genetic drift can have a _____ effect in a small population

Gene flow results when _____.

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

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

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

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

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

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

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

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

_____, 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.

_____ 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.

Study Notes

Selection Types and Genetic Variation

Phenotype Influence and Traits

Genetic Concepts

Evolutionary Mechanisms

Mechanisms and Allele Frequency Changes

Summarizing Change in Evolution

Studying That Suits You

Description

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Disruptive selection eliminates phenotypes near the __ and favors the _ phenotypes, resulting in __ in a population.

Stabilizing selection causes _; phenotypes become less common.

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

Gene flow can bring new alleles that are __, , or _ into a population

Different events and conditions result in ___, _, and __

___ 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.