BIO111 Exam 4 Actual Exam V3 | BIO111 General Biology (BIO111
Exam 4) | UCLA
1. Which of the following is the primary mechanism of adaptive evolution as proposed by
Charles Darwin?
A. Genetic drift
B. Mutation
C. Gene flow
D. Natural selection
Answer: D
Rationale: Natural selection is the process by which individuals with favorable traits are
more likely to survive and reproduce. This mechanism leads to the accumulation of
adaptations in a population over time. It is distinct from random processes like genetic drift
because it consistently leads to adaptive changes.
2. In a population at Hardy-Weinberg equilibrium, if the frequency of a recessive allele (q) is
0.3, what is the frequency of the homozygous dominant genotype?
A. 0.09
B. 0.49
C. 0.70
D. 0.21
Answer: B
Rationale: According to the Hardy-Weinberg formula, p plus q equals 1, so p must be 0.7.
The frequency of the homozygous dominant genotype is represented by p squared.
Calculating 0.7 squared yields 0.49 for the genotype frequency.
3. Which type of selection occurs when individuals at both extremes of a phenotypic range
are favored over intermediate phenotypes?
A. Disruptive selection
B. Directional selection
C. Stabilizing selection
D. Sexual selection
Answer: A
,Rationale: Disruptive selection favors individuals at both ends of the phenotypic spectrum.
This can lead to increased genetic variation within the population. Often, this type of
selection is a precursor to speciation events.
4. Which process is responsible for the movement of alleles between populations, potentially
reducing genetic differences between them?
A. Gene flow
B. Genetic drift
C. Natural selection
D. Non-random mating
Answer: A
Rationale: Gene flow occurs when individuals or their gametes move from one population
to another. This exchange of genetic material tends to homogenize the populations
involved. It can counteract the effects of natural selection and genetic drift by introducing
new alleles.
5. The sudden reduction in population size due to a natural disaster, leading to a change in
the allele frequencies, is known as:
A. The founder effect
B. Stabilizing selection
C. Assortative mating
D. The bottleneck effect
Answer: D
Rationale: The bottleneck effect happens when a large portion of a population is killed off
by a random event. The surviving individuals may not represent the original population’s
genetic diversity. This results in a significant loss of genetic variation and potentially high
frequencies of rare alleles.
6. Which species concept defines a species as a group of populations whose members have
the potential to interbreed and produce viable, fertile offspring?
A. Morphological species concept
B. Phylogenetic species concept
C. Biological species concept
D. Ecological species concept
Answer: C
, Rationale: The Biological Species Concept focuses on reproductive isolation rather than
physical appearance. It is the most widely used definition in evolutionary biology for sexual
organisms. However, it cannot be applied to fossils or asexually reproducing species.
7. What is the term for speciation that occurs when populations are geographically
separated?
A. Sympatric speciation
B. Polyploidy
C. Parapatric speciation
D. Allopatric speciation
Answer: D
Rationale: Allopatric speciation occurs when a physical barrier prevents gene flow
between populations. Over time, these isolated populations evolve independently through
mutation and selection. Eventually, they become reproductively isolated even if the barrier
is removed.
8. A structures that has no apparent function in a living organism but was functional in an
ancestor is called a:
A. Vestigial structure
B. Analogous structure
C. Homologous structure
D. Convergent structure
Answer: A
Rationale: Vestigial structures are remnants of features that served important functions in
an organism’s ancestors. Examples include the pelvic bones of whales and the human
appendix. They provide strong evidence for common descent and evolutionary change.
9. In a phylogenetic tree, a group that consists of an ancestral species and all its descendants
is called:
A. Polyphyletic
B. Paraphyletic
C. Monophyletic
D. Analogous
Answer: C
Exam 4) | UCLA
1. Which of the following is the primary mechanism of adaptive evolution as proposed by
Charles Darwin?
A. Genetic drift
B. Mutation
C. Gene flow
D. Natural selection
Answer: D
Rationale: Natural selection is the process by which individuals with favorable traits are
more likely to survive and reproduce. This mechanism leads to the accumulation of
adaptations in a population over time. It is distinct from random processes like genetic drift
because it consistently leads to adaptive changes.
2. In a population at Hardy-Weinberg equilibrium, if the frequency of a recessive allele (q) is
0.3, what is the frequency of the homozygous dominant genotype?
A. 0.09
B. 0.49
C. 0.70
D. 0.21
Answer: B
Rationale: According to the Hardy-Weinberg formula, p plus q equals 1, so p must be 0.7.
The frequency of the homozygous dominant genotype is represented by p squared.
Calculating 0.7 squared yields 0.49 for the genotype frequency.
3. Which type of selection occurs when individuals at both extremes of a phenotypic range
are favored over intermediate phenotypes?
A. Disruptive selection
B. Directional selection
C. Stabilizing selection
D. Sexual selection
Answer: A
,Rationale: Disruptive selection favors individuals at both ends of the phenotypic spectrum.
This can lead to increased genetic variation within the population. Often, this type of
selection is a precursor to speciation events.
4. Which process is responsible for the movement of alleles between populations, potentially
reducing genetic differences between them?
A. Gene flow
B. Genetic drift
C. Natural selection
D. Non-random mating
Answer: A
Rationale: Gene flow occurs when individuals or their gametes move from one population
to another. This exchange of genetic material tends to homogenize the populations
involved. It can counteract the effects of natural selection and genetic drift by introducing
new alleles.
5. The sudden reduction in population size due to a natural disaster, leading to a change in
the allele frequencies, is known as:
A. The founder effect
B. Stabilizing selection
C. Assortative mating
D. The bottleneck effect
Answer: D
Rationale: The bottleneck effect happens when a large portion of a population is killed off
by a random event. The surviving individuals may not represent the original population’s
genetic diversity. This results in a significant loss of genetic variation and potentially high
frequencies of rare alleles.
6. Which species concept defines a species as a group of populations whose members have
the potential to interbreed and produce viable, fertile offspring?
A. Morphological species concept
B. Phylogenetic species concept
C. Biological species concept
D. Ecological species concept
Answer: C
, Rationale: The Biological Species Concept focuses on reproductive isolation rather than
physical appearance. It is the most widely used definition in evolutionary biology for sexual
organisms. However, it cannot be applied to fossils or asexually reproducing species.
7. What is the term for speciation that occurs when populations are geographically
separated?
A. Sympatric speciation
B. Polyploidy
C. Parapatric speciation
D. Allopatric speciation
Answer: D
Rationale: Allopatric speciation occurs when a physical barrier prevents gene flow
between populations. Over time, these isolated populations evolve independently through
mutation and selection. Eventually, they become reproductively isolated even if the barrier
is removed.
8. A structures that has no apparent function in a living organism but was functional in an
ancestor is called a:
A. Vestigial structure
B. Analogous structure
C. Homologous structure
D. Convergent structure
Answer: A
Rationale: Vestigial structures are remnants of features that served important functions in
an organism’s ancestors. Examples include the pelvic bones of whales and the human
appendix. They provide strong evidence for common descent and evolutionary change.
9. In a phylogenetic tree, a group that consists of an ancestral species and all its descendants
is called:
A. Polyphyletic
B. Paraphyletic
C. Monophyletic
D. Analogous
Answer: C
