Biology 1002 Pomarico Test 3, BIO 1002 Exam 4
Pomarico LSU Latest (2024/2025) Comprehensive
Questions and Graded Answers | 100% Pass
Section 1: Evolution & Population Genetics (Questions 1–15)
1. Which of the following is NOT a condition of Hardy-Weinberg equilibrium?
• A) No mutation
• B) Large population size
• C) Natural selection
• D) Random mating
Answer: C (Natural selection)
Rationale: Hardy-Weinberg requires no natural selection. Other conditions: no gene flow, no
mutation, large population, random mating.
2. In a population of frogs, the allele frequency of A (dominant) is 0.7 and a (recessive) is 0.3.
Under Hardy-Weinberg, what is the frequency of heterozygous individuals?
• A) 0.09
• B) 0.42
• C) 0.49
• D) 0.21
Answer: B (0.42)
Rationale: Heterozygotes = 2pq = 2(0.7)(0.3) = 0.42.
3. Which evolutionary mechanism reduces genetic variation most rapidly in a small
population?
, • A) Mutation
• B) Gene flow
• C) Genetic drift
• D) Sexual selection
Answer: C (Genetic drift)
Rationale: Drift causes allele fixation/loss quickly in small populations, reducing variation.
4. A population of birds experiences a hurricane that randomly kills 90% of individuals. The
surviving population has different allele frequencies. This is an example of:
• A) Bottleneck effect
• B) Founder effect
• C) Gene flow
• D) Disruptive selection
Answer: A (Bottleneck effect)
Rationale: A drastic reduction in population size randomly alters allele frequencies.
5. Which type of selection favors intermediate phenotypes and reduces variation?
• A) Directional
• B) Disruptive
• C) Stabilizing
• D) Sexual
Answer: C (Stabilizing)
Rationale: Stabilizing selection favors mean trait values (e.g., human birth weight).
6. The biological species concept defines a species as:
• A) A group of organisms that look alike
• B) A group of populations that interbreed and produce fertile offspring
, • C) A group sharing a common ancestor
• D) A group occupying the same niche
Answer: B
Rationale: Ernst Mayr’s definition focuses on reproductive isolation.
7. Two species of squirrels are separated by the Grand Canyon. They diverged due to:
• A) Sympatric speciation
• B) Allopatric speciation
• C) Parapatric speciation
• D) Peripatric speciation
Answer: B (Allopatric speciation)
Rationale: Geographic barrier (canyon) prevents gene flow.
8. Which prezygotic isolating mechanism involves species breeding at different times of the
year?
• A) Mechanical isolation
• B) Gametic isolation
• C) Temporal isolation
• D) Behavioral isolation
Answer: C (Temporal isolation)
Rationale: Timing differences prevent mating.
9. In a population of beetles, green beetles survive better on leaves than brown beetles.
Over time, green allele frequency increases. This is:
• A) Genetic drift
• B) Natural selection
• C) Mutation pressure
• D) Gene flow
, Answer: B
Rationale: Differential survival/reproduction based on heritable trait.
10. The total collection of alleles in a population is called the:
• A) Genotype frequency
• B) Gene pool
• C) Phenome
• D) Genomic library
Answer: B
Rationale: Gene pool = sum of all alleles in a population.
11. Which of the following is an example of postzygotic isolation?
• A) Different mating calls
• B) Sperm cannot fertilize egg
• C) Hybrid offspring are sterile (e.g., mule)
• D) Different habitats
Answer: C
Rationale: Postzygotic barriers act after zygote formation (hybrid inviability/sterility).
12. In Hardy-Weinberg, if p = 0.6, then q = ?
• A) 0.4
• B) 0.6
• C) 0.16
• D) 0.36
Answer: A
Rationale: p + q = 1, so q = 1 – 0.6 = 0.4.
13. Which of the following is NOT a source of genetic variation?
Pomarico LSU Latest (2024/2025) Comprehensive
Questions and Graded Answers | 100% Pass
Section 1: Evolution & Population Genetics (Questions 1–15)
1. Which of the following is NOT a condition of Hardy-Weinberg equilibrium?
• A) No mutation
• B) Large population size
• C) Natural selection
• D) Random mating
Answer: C (Natural selection)
Rationale: Hardy-Weinberg requires no natural selection. Other conditions: no gene flow, no
mutation, large population, random mating.
2. In a population of frogs, the allele frequency of A (dominant) is 0.7 and a (recessive) is 0.3.
Under Hardy-Weinberg, what is the frequency of heterozygous individuals?
• A) 0.09
• B) 0.42
• C) 0.49
• D) 0.21
Answer: B (0.42)
Rationale: Heterozygotes = 2pq = 2(0.7)(0.3) = 0.42.
3. Which evolutionary mechanism reduces genetic variation most rapidly in a small
population?
, • A) Mutation
• B) Gene flow
• C) Genetic drift
• D) Sexual selection
Answer: C (Genetic drift)
Rationale: Drift causes allele fixation/loss quickly in small populations, reducing variation.
4. A population of birds experiences a hurricane that randomly kills 90% of individuals. The
surviving population has different allele frequencies. This is an example of:
• A) Bottleneck effect
• B) Founder effect
• C) Gene flow
• D) Disruptive selection
Answer: A (Bottleneck effect)
Rationale: A drastic reduction in population size randomly alters allele frequencies.
5. Which type of selection favors intermediate phenotypes and reduces variation?
• A) Directional
• B) Disruptive
• C) Stabilizing
• D) Sexual
Answer: C (Stabilizing)
Rationale: Stabilizing selection favors mean trait values (e.g., human birth weight).
6. The biological species concept defines a species as:
• A) A group of organisms that look alike
• B) A group of populations that interbreed and produce fertile offspring
, • C) A group sharing a common ancestor
• D) A group occupying the same niche
Answer: B
Rationale: Ernst Mayr’s definition focuses on reproductive isolation.
7. Two species of squirrels are separated by the Grand Canyon. They diverged due to:
• A) Sympatric speciation
• B) Allopatric speciation
• C) Parapatric speciation
• D) Peripatric speciation
Answer: B (Allopatric speciation)
Rationale: Geographic barrier (canyon) prevents gene flow.
8. Which prezygotic isolating mechanism involves species breeding at different times of the
year?
• A) Mechanical isolation
• B) Gametic isolation
• C) Temporal isolation
• D) Behavioral isolation
Answer: C (Temporal isolation)
Rationale: Timing differences prevent mating.
9. In a population of beetles, green beetles survive better on leaves than brown beetles.
Over time, green allele frequency increases. This is:
• A) Genetic drift
• B) Natural selection
• C) Mutation pressure
• D) Gene flow
, Answer: B
Rationale: Differential survival/reproduction based on heritable trait.
10. The total collection of alleles in a population is called the:
• A) Genotype frequency
• B) Gene pool
• C) Phenome
• D) Genomic library
Answer: B
Rationale: Gene pool = sum of all alleles in a population.
11. Which of the following is an example of postzygotic isolation?
• A) Different mating calls
• B) Sperm cannot fertilize egg
• C) Hybrid offspring are sterile (e.g., mule)
• D) Different habitats
Answer: C
Rationale: Postzygotic barriers act after zygote formation (hybrid inviability/sterility).
12. In Hardy-Weinberg, if p = 0.6, then q = ?
• A) 0.4
• B) 0.6
• C) 0.16
• D) 0.36
Answer: A
Rationale: p + q = 1, so q = 1 – 0.6 = 0.4.
13. Which of the following is NOT a source of genetic variation?
