Understanding Evolution and Natural Selection

What is the primary mechanism by which evolution occurs according to Darwin's theory?

• Genetic Drift

• Natural Selection

• Gene Flow

• Mutation

Answer explanation

According to Darwin's theory, evolution primarily occurs through natural selection, where individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.

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

• Non-random mating

• Large population size

• High mutation rate

• High gene flow

Answer explanation

A condition for Hardy-Weinberg equilibrium is a large population size, which minimizes genetic drift. Non-random mating, high mutation rates, and high gene flow disrupt this equilibrium.

How does gene flow affect the genetic variation between two populations?

• Increases variation within populations and decreases variation between them

• Decreases variation within populations and increases variation between them

• Has no effect on genetic variation

• Increases variation both within and between populations

Answer explanation

Gene flow introduces new alleles into a population, increasing genetic variation within that population. As alleles are shared between populations, it reduces the genetic differences between them, thus decreasing variation between populations.

Explain how a bottleneck effect can impact a population's genetic diversity.

• It increases genetic diversity by introducing new alleles.

• It reduces genetic diversity by drastically reducing population size.

• It maintains genetic diversity by stabilizing allele frequencies.

• It has no impact on genetic diversity.

Answer explanation

The bottleneck effect occurs when a population's size is drastically reduced, leading to a loss of genetic diversity. This reduction limits the gene pool, resulting in fewer alleles and decreased variability within the population.

Which type of natural selection favors individuals with extreme phenotypes over those with intermediate phenotypes?

• Stabilizing Selection

• Disruptive Selection

• Directional Selection

• Balancing Selection

Answer explanation

Disruptive Selection favors extreme phenotypes, leading to a population with two or more distinct forms. In contrast, Stabilizing Selection favors intermediate phenotypes, while Directional Selection favors one extreme.

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NGSS.HS-LS4-4

Describe how the founder's effect can lead to genetic differences in a new population.

• It results in a new population with genetic diversity similar to the original population.

• It leads to a new population with reduced genetic diversity and different allele frequencies.

• It causes the new population to have increased genetic diversity.

• It has no effect on the genetic makeup of the new population.

Answer explanation

The founder's effect occurs when a small group establishes a new population, leading to reduced genetic diversity and altered allele frequencies compared to the original population, as only a subset of alleles is represented.

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NGSS.HS-LS4-2

What is an example of a structural adaptation in animals?

• Migration patterns

• Camouflage

• Hibernation

• Photosynthesis

Answer explanation

Camouflage is a structural adaptation that helps animals blend into their environment, enhancing their ability to avoid predators or ambush prey. Unlike migration, hibernation, or photosynthesis, it involves physical traits.

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NGSS.HS-LS4-4

How does variation within a population contribute to natural selection?

• It decreases the chances of survival for all individuals.

• It provides a basis for individuals to adapt to changing environments.

• It ensures that all individuals are identical.

• It has no impact on natural selection.

Answer explanation

Variation within a population allows individuals to possess different traits, which can enhance their ability to survive and reproduce in changing environments, thus driving natural selection.

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NGSS.HS-LS4-2

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Calculate the expected frequency of the homozygous recessive genotype in a population in Hardy-Weinberg equilibrium if the frequency of the recessive allele is 0.3.

• 0.09

• 0.21

• 0.49

• 0.7

Answer explanation

In Hardy-Weinberg equilibrium, the frequency of the homozygous recessive genotype (aa) is q². Given the recessive allele frequency (q) is 0.3, calculate q²: (0.3)² = 0.09. Thus, the expected frequency is 0.09.

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Which of the following is an example of behavioral adaptation?

• Thick fur in polar bears

• Birds migrating south for the winter

• Cacti having spines

• Fish having gills

Answer explanation

Birds migrating south for the winter is a behavioral adaptation, as it involves changes in behavior to survive seasonal changes. In contrast, thick fur, spines, and gills are physical adaptations.