BIOD 102 BIOLOGY II MODULE 1 EXAM 2026/2027 | Portage
Learning Complete Solutions | Evolution, Population
Genetics, Speciation, Ecology | Pass Guaranteed - A+
Graded
Domain 1: Evolution & Natural Selection (10 Questions)
Q1: A population of beetles exhibits variation in color: some are dark brown, some are
light brown, and some are medium brown. The environment is a forest floor with dark
soil. Over several generations, the frequency of dark brown beetles increases
significantly while light brown beetles decrease. Which evolutionary mechanism best
explains this observation?
A. Genetic drift due to random sampling of alleles
B. Natural selection favoring camouflaged individuals [CORRECT]
C. Gene flow from a neighboring population of dark beetles
D. Mutation creating new dark color alleles
Correct Answer: B
Rationale: This scenario demonstrates natural selection: variation exists in the
population (color variation), the variation is heritable, and there is differential
survival/reproduction (dark beetles are better camouflaged from predators, survive
longer, and leave more offspring). The environment (dark soil) creates selective
pressure favoring dark coloration. Genetic drift (A) would cause random changes, not
consistent directional change toward dark color. Gene flow (C) is not mentioned and
would require migration. Mutation (D) is the ultimate source of variation but doesn't
explain the directional frequency change over generations.
,Q2: In a population of finches, those with larger, deeper beaks are better able to crack
hard seeds during a drought when soft seeds are scarce. Over time, the average beak
size increases in the population. Which component of natural selection does this
scenario best illustrate?
A. Stabilizing selection
B. Directional selection [CORRECT]
C. Disruptive selection
D. Balancing selection
Correct Answer: B
Rationale: Directional selection occurs when environmental conditions favor individuals
at one extreme of a phenotypic distribution, causing the population mean to shift in that
direction. Here, drought conditions favor larger, deeper beaks (one extreme), shifting the
population toward larger beak size. Stabilizing selection (A) favors intermediate
phenotypes and reduces variation. Disruptive selection (C) favors both extremes over
intermediates. Balancing selection (D) maintains multiple alleles in a population (e.g.,
heterozygote advantage).
Q3: Which of the following is NOT a requirement for natural selection to occur?
A. Variation in traits among individuals
B. Heritability of traits from parents to offspring
C. Differential survival and reproduction based on traits
D. Genetic mutation occurring in every individual every generation [CORRECT]
,Correct Answer: D
Rationale: Natural selection requires: (1) variation in heritable traits, (2) differential
survival/reproduction based on those traits, leading to adaptation. While mutation is the
ultimate source of genetic variation, it is NOT required that every individual mutate every
generation. Selection can act on existing variation for many generations without new
mutations. Variation (A), heritability (B), and differential reproduction (C) are all
essential components of natural selection.
Q4: The fossil record shows that modern horses (Equus) evolved from small, multi-toed
ancestors (Hyracotherium) over 55 million years. This evolutionary history
demonstrates which pattern?
A. Convergent evolution
B. Adaptive radiation
C. Gradualistic evolution with structural modifications for grassland habitat [CORRECT]
D. Punctuated equilibrium with rapid saltational changes
Correct Answer: C
Rationale: Horse evolution demonstrates gradualistic evolution: progressive changes
over long periods, including increase in body size, reduction in toe number (from 4 toes
to 1 hoof), and elongation of limbs for running on grasslands. The fossil record shows
intermediate forms spanning millions of years. Convergent evolution (A) involves
unrelated lineages developing similar traits. Adaptive radiation (B) is rapid
diversification into multiple forms (not seen here). Punctuated equilibrium (D) involves
long stasis and rapid change, not the gradual pattern seen in horse evolution.
, Q5: Which evidence for evolution is demonstrated when comparing the forelimb bones
of humans, whales, bats, and cats, which show the same bone pattern (humerus, radius,
ulna, carpals, metacarpals, phalanges) despite different functions?
A. Molecular homology
B. Vestigial structures
C. Homologous structures indicating common ancestry [CORRECT]
D. Analogous structures indicating convergent evolution
Correct Answer: C
Rationale: Homologous structures share underlying structural similarity due to common
ancestry, even when adapted for different functions. The pentadactyl limb pattern in
vertebrates is a classic example—modified for grasping (humans), swimming (whales),
flying (bats), and walking (cats). This structural similarity despite functional divergence
indicates shared ancestry. Molecular homology (A) refers to DNA/protein similarities.
Vestigial structures (B) are non-functional remnants (e.g., appendix). Analogous
structures (D) have similar function but different structure/origin (e.g., bird wing and
insect wing).
Q6: Peahens (female peacocks) preferentially mate with males that have the most
elaborate, colorful tail feathers. Over generations, males develop increasingly elaborate
tails, even though these tails reduce survival by making flight difficult. Which
evolutionary mechanism explains this?
A. Natural selection for survival
B. Sexual selection through female choice (intersexual selection) [CORRECT]
Learning Complete Solutions | Evolution, Population
Genetics, Speciation, Ecology | Pass Guaranteed - A+
Graded
Domain 1: Evolution & Natural Selection (10 Questions)
Q1: A population of beetles exhibits variation in color: some are dark brown, some are
light brown, and some are medium brown. The environment is a forest floor with dark
soil. Over several generations, the frequency of dark brown beetles increases
significantly while light brown beetles decrease. Which evolutionary mechanism best
explains this observation?
A. Genetic drift due to random sampling of alleles
B. Natural selection favoring camouflaged individuals [CORRECT]
C. Gene flow from a neighboring population of dark beetles
D. Mutation creating new dark color alleles
Correct Answer: B
Rationale: This scenario demonstrates natural selection: variation exists in the
population (color variation), the variation is heritable, and there is differential
survival/reproduction (dark beetles are better camouflaged from predators, survive
longer, and leave more offspring). The environment (dark soil) creates selective
pressure favoring dark coloration. Genetic drift (A) would cause random changes, not
consistent directional change toward dark color. Gene flow (C) is not mentioned and
would require migration. Mutation (D) is the ultimate source of variation but doesn't
explain the directional frequency change over generations.
,Q2: In a population of finches, those with larger, deeper beaks are better able to crack
hard seeds during a drought when soft seeds are scarce. Over time, the average beak
size increases in the population. Which component of natural selection does this
scenario best illustrate?
A. Stabilizing selection
B. Directional selection [CORRECT]
C. Disruptive selection
D. Balancing selection
Correct Answer: B
Rationale: Directional selection occurs when environmental conditions favor individuals
at one extreme of a phenotypic distribution, causing the population mean to shift in that
direction. Here, drought conditions favor larger, deeper beaks (one extreme), shifting the
population toward larger beak size. Stabilizing selection (A) favors intermediate
phenotypes and reduces variation. Disruptive selection (C) favors both extremes over
intermediates. Balancing selection (D) maintains multiple alleles in a population (e.g.,
heterozygote advantage).
Q3: Which of the following is NOT a requirement for natural selection to occur?
A. Variation in traits among individuals
B. Heritability of traits from parents to offspring
C. Differential survival and reproduction based on traits
D. Genetic mutation occurring in every individual every generation [CORRECT]
,Correct Answer: D
Rationale: Natural selection requires: (1) variation in heritable traits, (2) differential
survival/reproduction based on those traits, leading to adaptation. While mutation is the
ultimate source of genetic variation, it is NOT required that every individual mutate every
generation. Selection can act on existing variation for many generations without new
mutations. Variation (A), heritability (B), and differential reproduction (C) are all
essential components of natural selection.
Q4: The fossil record shows that modern horses (Equus) evolved from small, multi-toed
ancestors (Hyracotherium) over 55 million years. This evolutionary history
demonstrates which pattern?
A. Convergent evolution
B. Adaptive radiation
C. Gradualistic evolution with structural modifications for grassland habitat [CORRECT]
D. Punctuated equilibrium with rapid saltational changes
Correct Answer: C
Rationale: Horse evolution demonstrates gradualistic evolution: progressive changes
over long periods, including increase in body size, reduction in toe number (from 4 toes
to 1 hoof), and elongation of limbs for running on grasslands. The fossil record shows
intermediate forms spanning millions of years. Convergent evolution (A) involves
unrelated lineages developing similar traits. Adaptive radiation (B) is rapid
diversification into multiple forms (not seen here). Punctuated equilibrium (D) involves
long stasis and rapid change, not the gradual pattern seen in horse evolution.
, Q5: Which evidence for evolution is demonstrated when comparing the forelimb bones
of humans, whales, bats, and cats, which show the same bone pattern (humerus, radius,
ulna, carpals, metacarpals, phalanges) despite different functions?
A. Molecular homology
B. Vestigial structures
C. Homologous structures indicating common ancestry [CORRECT]
D. Analogous structures indicating convergent evolution
Correct Answer: C
Rationale: Homologous structures share underlying structural similarity due to common
ancestry, even when adapted for different functions. The pentadactyl limb pattern in
vertebrates is a classic example—modified for grasping (humans), swimming (whales),
flying (bats), and walking (cats). This structural similarity despite functional divergence
indicates shared ancestry. Molecular homology (A) refers to DNA/protein similarities.
Vestigial structures (B) are non-functional remnants (e.g., appendix). Analogous
structures (D) have similar function but different structure/origin (e.g., bird wing and
insect wing).
Q6: Peahens (female peacocks) preferentially mate with males that have the most
elaborate, colorful tail feathers. Over generations, males develop increasingly elaborate
tails, even though these tails reduce survival by making flight difficult. Which
evolutionary mechanism explains this?
A. Natural selection for survival
B. Sexual selection through female choice (intersexual selection) [CORRECT]
