PCB 4674 | PCB4674 Exam 1: Evolution Updated
and Latest Questions and Correct Answers with
Rationale - Florida State University
1. Which of the following is a primary requirement for natural selection to occur within a
population?
A. The population must be in Hardy-Weinberg equilibrium.
B. Environmental conditions must remain constant over time.
C. Genetic variation must exist among individuals in the population.
D. Mutations must occur at a high rate to provide new traits.
Correct Answer: C
Expert Explanation: Natural selection depends on the presence of heritable differences
among individuals to function. Without genetic variation, every individual would have the
same fitness, preventing selection. These variations must lead to differential reproductive
success for evolution to proceed. While mutations provide new variation, they do not need
to occur at a high rate. Therefore, variation is the foundational raw material for the process
of natural selection.
2. In a small population of island lizards, a sudden hurricane kills 90% of the individuals. This
is an example of:
A. A population bottleneck.
B. Directional selection.
C. The founder effect.
D. Gene flow.
Correct Answer: A
Expert Explanation: A population bottleneck occurs when a disaster drastically reduces
the number of individuals in a population. This event leads to a random loss of genetic
diversity because the survivors represent only a fraction of the original gene pool. The
resulting allele frequencies often differ significantly from the pre-disaster population.
Unlike selection, this process is purely stochastic and does not favor specific adaptations. It
is a specific form of genetic drift that can have long-term evolutionary consequences.
3. Which mechanism of evolution is most likely to reduce genetic differences between two
separate populations?
A. Natural Selection
B. Genetic Drift
,C. Mutation
D. Gene Flow
Correct Answer: D
Expert Explanation: Gene flow involves the transfer of alleles between populations
through the migration of individuals or gametes. This process introduces new genetic
material and blends the gene pools of the involved populations. Over time, consistent gene
flow makes the populations more genetically similar to one another. It can counteract the
effects of local selection and genetic drift that cause populations to diverge. Thus, gene flow
acts as a homogenizing force in evolutionary biology.
4. What does the ‘fitness’ of an individual measure in an evolutionary context?
A. The physical strength and speed of the individual compared to others.
B. The ability of the individual to survive for the longest possible lifespan.
C. The number of mutations an individual accumulates during its lifetime.
D. The relative contribution of an individual to the gene pool of the next generation.
Correct Answer: D
Expert Explanation: Fitness is defined by the reproductive success of an individual
relative to others in the population. It encompasses both survival and the ability to produce
viable, fertile offspring. An individual that lives long but fails to reproduce has a fitness of
zero. Survival is only important insofar as it allows for the eventual transmission of genes.
Therefore, high fitness reflects the successful passage of an individual’s traits to future
generations.
5. Darwin’s concept of ‘descent with modification’ primarily suggests that:
A. Species remain unchanged over time unless a major mutation occurs.
B. All organisms share a common ancestor and change over many generations.
C. Evolution occurs through the inheritance of acquired characteristics.
D. Life was created in its current form and does not change.
Correct Answer: B
Expert Explanation: Descent with modification is the core idea that all life is linked by
common ancestry. It describes how species accumulate changes over long periods as they
adapt to different environments. This process leads to the diversity of life observed in the
fossil record and today. Unlike Lamarckian theory, it emphasizes that changes occur across
generations rather than within a single lifetime. It serves as the fundamental framework for
the modern theory of evolution.
, 6. A population of birds shows a preference for mates with the brightest feathers. This is an
example of:
A. Disruptive selection
B. Sexual selection
C. Stabilizing selection
D. Genetic drift
Correct Answer: B
Expert Explanation: Sexual selection is a form of natural selection where individuals with
certain inherited characteristics are more likely to obtain mates. In this scenario, the bright
feathers serve as a signal of quality or attractiveness to potential partners. This can lead to
the evolution of elaborate traits that might otherwise be disadvantageous for survival. It
results in differential reproductive success based on mating preference rather than just
environmental survival. Sexual selection is responsible for much of the ornamentation seen
in the animal kingdom.
7. Which of the following is true regarding the Hardy-Weinberg equilibrium?
A. It describes a population that is actively evolving.
B. It requires a small population size to maintain allele frequencies.
C. It assumes that mutations and natural selection are occurring.
D. It serves as a null model to identify if evolutionary forces are acting.
Correct Answer: D
Expert Explanation: The Hardy-Weinberg equilibrium provides a mathematical baseline
for a population that is not evolving. For the equilibrium to hold, several strict assumptions
like no selection and no migration must be met. When the observed allele frequencies
deviate from the model, scientists can conclude that evolution is occurring. This allows
researchers to pinpoint which evolutionary forces might be influencing the population. It is
an essential tool for quantifying the rate and direction of evolutionary change.
8. Stabilizing selection differs from directional selection because it:
A. Favors both extreme phenotypes over the intermediate ones.
B. Favors the intermediate phenotype and reduces phenotypic variation.
C. Favors one extreme phenotype over all others in the population.
D. Increases the overall genetic variation within the population.
Correct Answer: B
Expert Explanation: Stabilizing selection acts against extreme phenotypes and favors the
average or intermediate traits. This process typically occurs in stable environments where
and Latest Questions and Correct Answers with
Rationale - Florida State University
1. Which of the following is a primary requirement for natural selection to occur within a
population?
A. The population must be in Hardy-Weinberg equilibrium.
B. Environmental conditions must remain constant over time.
C. Genetic variation must exist among individuals in the population.
D. Mutations must occur at a high rate to provide new traits.
Correct Answer: C
Expert Explanation: Natural selection depends on the presence of heritable differences
among individuals to function. Without genetic variation, every individual would have the
same fitness, preventing selection. These variations must lead to differential reproductive
success for evolution to proceed. While mutations provide new variation, they do not need
to occur at a high rate. Therefore, variation is the foundational raw material for the process
of natural selection.
2. In a small population of island lizards, a sudden hurricane kills 90% of the individuals. This
is an example of:
A. A population bottleneck.
B. Directional selection.
C. The founder effect.
D. Gene flow.
Correct Answer: A
Expert Explanation: A population bottleneck occurs when a disaster drastically reduces
the number of individuals in a population. This event leads to a random loss of genetic
diversity because the survivors represent only a fraction of the original gene pool. The
resulting allele frequencies often differ significantly from the pre-disaster population.
Unlike selection, this process is purely stochastic and does not favor specific adaptations. It
is a specific form of genetic drift that can have long-term evolutionary consequences.
3. Which mechanism of evolution is most likely to reduce genetic differences between two
separate populations?
A. Natural Selection
B. Genetic Drift
,C. Mutation
D. Gene Flow
Correct Answer: D
Expert Explanation: Gene flow involves the transfer of alleles between populations
through the migration of individuals or gametes. This process introduces new genetic
material and blends the gene pools of the involved populations. Over time, consistent gene
flow makes the populations more genetically similar to one another. It can counteract the
effects of local selection and genetic drift that cause populations to diverge. Thus, gene flow
acts as a homogenizing force in evolutionary biology.
4. What does the ‘fitness’ of an individual measure in an evolutionary context?
A. The physical strength and speed of the individual compared to others.
B. The ability of the individual to survive for the longest possible lifespan.
C. The number of mutations an individual accumulates during its lifetime.
D. The relative contribution of an individual to the gene pool of the next generation.
Correct Answer: D
Expert Explanation: Fitness is defined by the reproductive success of an individual
relative to others in the population. It encompasses both survival and the ability to produce
viable, fertile offspring. An individual that lives long but fails to reproduce has a fitness of
zero. Survival is only important insofar as it allows for the eventual transmission of genes.
Therefore, high fitness reflects the successful passage of an individual’s traits to future
generations.
5. Darwin’s concept of ‘descent with modification’ primarily suggests that:
A. Species remain unchanged over time unless a major mutation occurs.
B. All organisms share a common ancestor and change over many generations.
C. Evolution occurs through the inheritance of acquired characteristics.
D. Life was created in its current form and does not change.
Correct Answer: B
Expert Explanation: Descent with modification is the core idea that all life is linked by
common ancestry. It describes how species accumulate changes over long periods as they
adapt to different environments. This process leads to the diversity of life observed in the
fossil record and today. Unlike Lamarckian theory, it emphasizes that changes occur across
generations rather than within a single lifetime. It serves as the fundamental framework for
the modern theory of evolution.
, 6. A population of birds shows a preference for mates with the brightest feathers. This is an
example of:
A. Disruptive selection
B. Sexual selection
C. Stabilizing selection
D. Genetic drift
Correct Answer: B
Expert Explanation: Sexual selection is a form of natural selection where individuals with
certain inherited characteristics are more likely to obtain mates. In this scenario, the bright
feathers serve as a signal of quality or attractiveness to potential partners. This can lead to
the evolution of elaborate traits that might otherwise be disadvantageous for survival. It
results in differential reproductive success based on mating preference rather than just
environmental survival. Sexual selection is responsible for much of the ornamentation seen
in the animal kingdom.
7. Which of the following is true regarding the Hardy-Weinberg equilibrium?
A. It describes a population that is actively evolving.
B. It requires a small population size to maintain allele frequencies.
C. It assumes that mutations and natural selection are occurring.
D. It serves as a null model to identify if evolutionary forces are acting.
Correct Answer: D
Expert Explanation: The Hardy-Weinberg equilibrium provides a mathematical baseline
for a population that is not evolving. For the equilibrium to hold, several strict assumptions
like no selection and no migration must be met. When the observed allele frequencies
deviate from the model, scientists can conclude that evolution is occurring. This allows
researchers to pinpoint which evolutionary forces might be influencing the population. It is
an essential tool for quantifying the rate and direction of evolutionary change.
8. Stabilizing selection differs from directional selection because it:
A. Favors both extreme phenotypes over the intermediate ones.
B. Favors the intermediate phenotype and reduces phenotypic variation.
C. Favors one extreme phenotype over all others in the population.
D. Increases the overall genetic variation within the population.
Correct Answer: B
Expert Explanation: Stabilizing selection acts against extreme phenotypes and favors the
average or intermediate traits. This process typically occurs in stable environments where
