Q: A population of beetles has two alleles for color: B (black) and b (brown). If the frequency of B is $$p = 0.7$$ and the frequency of b is $$q = 0.3$$, what is the expected frequency of heterozygotes (Bb) under Hardy-Weinberg equilibrium?

$$2pq = 2 \times 0.7 \times 0.3 = 0.42$$

Q: In a population of 1000 individuals, 360 are homozygous for the red allele (RR), 480 are heterozygous (Rr), and 160 are homozygous for the white allele (rr). What is the frequency of the r allele?

$$q = \frac{2 \times 160 + 480}{2 \times 1000} = \frac{320 + 480}{2000} = \frac{800}{2000} = 0.4$$

Q: In a population, the frequency of a recessive genetic disease is $$q^2 = 0.04$. Assuming Hardy-Weinberg equilibrium, what is the expected frequency of carriers (heterozygotes)?

$$2pq = 2 \times 0.2 \times 0.8 = 0.32$$

Question 1

Which of the following best describes microevolution?

Accepted Answer

The change in allele frequencies within a population over generations.

Question 2

A population of beetles has two alleles for color: B (black) and b (brown). If the frequency of B is $$p = 0.7$$ and the frequency of b is $$q = 0.3$$, what is the expected frequency of heterozygotes (Bb) under Hardy-Weinberg equilibrium?

Accepted Answer

$$2pq = 2 	imes 0.7 	imes 0.3 = 0.42$$

Question 3

Which mechanism of evolution is most likely responsible for a sudden reduction in genetic diversity due to a natural disaster that drastically reduces population size?

Accepted Answer

Genetic drift (bottleneck effect)

Question 4

In a population of 1000 individuals, 360 are homozygous for the red allele (RR), 480 are heterozygous (Rr), and 160 are homozygous for the white allele (rr). What is the frequency of the r allele?

Accepted Answer

$$q = \frac{2 	imes 160 + 480}{2 	imes 1000} = \frac{320 + 480}{2000} = \frac{800}{2000} = 0.4$$

Question 5

Which of the following scenarios is an example of gene flow?

Accepted Answer

Two previously isolated rabbit populations begin to interbreed after a barrier is removed.

Question 6

If a population is in Hardy-Weinberg equilibrium, which of the following must be true?

Accepted Answer

Allele and genotype frequencies remain constant from generation to generation.

Question 7

A population of mice has the following genotype frequencies: $$AA = 0.25$$, $$Aa = 0.50$$, $$aa = 0.25. $$What are the allele frequencies of A and a?

Accepted Answer

$$p = 0.5$$, $$q = 0.5$$

Question 8

Which type of natural selection is occurring if individuals with intermediate phenotypes are favored over those with extreme phenotypes?

Accepted Answer

Stabilizing selection

Question 9

In a population, the frequency of a recessive genetic disease is $$q^2 = 0.04$. Assuming Hardy-Weinberg equilibrium, what is the expected frequency of carriers (heterozygotes)?

Accepted Answer

$$2pq = 2 	imes 0.2 	imes 0.8 = 0.32$$

Question 10

Which of the following increases the amount of genetic variation in a population?

Accepted Answer

Mutation

Question 11

A small group of lizards is blown by a storm to a new island, where they establish a new population. Over time, the allele frequencies in this new population differ from the original. What is this an example of?

Accepted Answer

Founder effect

Question 12

Which of the following is NOT an assumption of Hardy-Weinberg equilibrium?

Accepted Answer

Natural selection is acting on the population.

Question 13

In a population of 500 individuals, 5 are homozygous recessive for a trait. Assuming Hardy-Weinberg equilibrium, what is the frequency of the recessive allele?

Accepted Answer

$$q = \sqrt{\frac{5}{500}} = \sqrt{0.01} = 0.1$$

Question 14

Which of the following best explains why harmful recessive alleles can persist in a population?

Accepted Answer

They can be maintained by heterozygote advantage or balancing selection.

Question 15

A population of birds experiences a drought, and only those with the largest and smallest beaks survive, while those with intermediate beak sizes die. What type of selection is this?

Accepted Answer

Disruptive selection

Question 16

If a population is not evolving, what should be true about the observed and expected genotype frequencies?

Accepted Answer

They should be equal, matching Hardy-Weinberg predictions.

Question 17

Which of the following is an example of balancing selection?

Accepted Answer

Heterozygote advantage in sickle cell anemia, where carriers are resistant to malaria.

Question 18

A population of 1000 individuals has the following genotype counts: 490 AA, 420 Aa, and 90 aa. What is the frequency of the A allele?

Accepted Answer

$$p = \frac{2 	imes 490 + 420}{2 	imes 1000} = \frac{980 + 420}{2000} = \frac{1400}{2000} = 0.7$$

Question 19

Which mechanism of evolution is most likely to decrease genetic variation in a small population due to random chance?

Accepted Answer

Genetic drift

Question 20

Which of the following is a real-world example of directional selection?

Accepted Answer

Peppered moths in industrial England, where dark-colored moths became more common due to pollution.

Evolution of Populations and Population Genetics

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