Q: A population of 100 plants has the following genotype counts for a flower color gene: 36 red (RR), 48 pink (Rr), and 16 white (rr). What is the frequency of the r allele in this population? Use the formula $$q = \frac{2N_{rr} + N_{Rr}}{2N_{total}}.$$

$$q = \frac{2 \times 16 + 48}{2 \times 100} = \frac{32 + 48}{200} = \frac{80}{200} = 0.40$$

Q: A population is in Hardy-Weinberg equilibrium for a gene with two alleles, $$A$$ and $$a. If$$ $$p = 0.6$$ and $$q = 0.4$$, what is the expected frequency of heterozygotes ($$Aa$$)? Use the formula $$2pq.$$

$$2pq = 2 \times 0.6 \times 0.4 = 0.48$$

Q: A population of 200 individuals has the following genotype frequencies for a gene: $$AA = 0.25$$, $$Aa = 0.50$$, $$aa = 0.25. $$What is the frequency of the $$A$$ allele? Use the formula $$p = \frac{2N_{AA} + N_{Aa}}{2N_{total}}.$$

$$p = \frac{2 \times 0.25 \times 200 + 0.5 \times 200}{2 \times 200} = \frac{100 + 100}{400} = \frac{200}{400} = 0.5$$

Question 1

Which of the following best explains why genetic variation within a population is necessary for natural selection to occur?

Accepted Answer

Genetic variation provides different traits that may confer survival or reproductive advantages in changing environments.

Question 2

A population of 100 plants has the following genotype counts for a flower color gene: 36 red (RR), 48 pink (Rr), and 16 white (rr). What is the frequency of the r allele in this population? Use the formula $$q = \frac{2N_{rr} + N_{Rr}}{2N_{total}}.$$

Accepted Answer

$$q = \frac{2 	imes 16 + 48}{2 	imes 100} = \frac{32 + 48}{200} = \frac{80}{200} = 0.40$$

Question 3

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

Accepted Answer

Natural selection occurs.

Question 4

In a population of humans, the frequency of the dominant allele $$E$$ for earwax type is 0.8. What is the frequency of the recessive allele $$e$$?

Accepted Answer

$$q = 1 - p = 1 - 0.8 = 0.2$$

Question 5

Which pattern of natural selection is illustrated by the increase in frequency of dark-colored peppered moths in polluted environments?

Accepted Answer

Directional selection

Question 6

A population is in Hardy-Weinberg equilibrium for a gene with two alleles, $$A$$ and $$a. If$$ $$p = 0.6$$ and $$q = 0.4$$, what is the expected frequency of heterozygotes ($$Aa$$)? Use the formula $$2pq.$$

Accepted Answer

$$2pq = 2 	imes 0.6 	imes 0.4 = 0.48$$

Question 7

Which of the following scenarios best describes genetic drift?

Accepted Answer

A population of birds is reduced by a hurricane, and the surviving birds have different allele frequencies than the original population.

Question 8

Which of the following is an example of stabilizing selection?

Accepted Answer

Birds with intermediate clutch sizes have higher survival rates than those with very small or very large clutch sizes.

Question 9

Which mechanism of evolution tends to reduce genetic differences between populations?

Accepted Answer

Migration (gene flow)

Question 10

In a population affected by balancing selection due to malaria, 9% of individuals have sickle cell disease (homozygous recessive). What percentage of the population is malaria resistant (heterozygotes)? Use the Hardy-Weinberg equation: $$q^2 = 0.09$, 2pq$$ = ?$$.

Accepted Answer

$$q = \sqrt{0.09} = 0.3$$, $$p = 1 - 0.3 = 0.7$$, $$2pq = 2 	imes 0.7 	imes 0.3 = 0.42 or 42$$%

Question 11

Which of the following best describes the founder effect?

Accepted Answer

A small group separates from a larger population and establishes a new population with different allele frequencies.

Question 12

Which type of sexual selection involves direct competition between members of the same sex for mates?

Accepted Answer

Intrasexual selection

Question 13

Which evolutionary process is most likely to result in the fixation or loss of alleles in a small population over a short period of time?

Accepted Answer

Genetic drift

Question 14

A population of 200 individuals has the following genotype frequencies for a gene: $$AA = 0.25$$, $$Aa = 0.50$$, $$aa = 0.25. $$What is the frequency of the $$A$$ allele? Use the formula $$p = \frac{2N_{AA} + N_{Aa}}{2N_{total}}.$$

Accepted Answer

$$p = \frac{2 	imes 0.25 	imes 200 + 0.5 	imes 200}{2 	imes 200} = \frac{100 + 100}{400} = \frac{200}{400} = 0.5$$

Question 15

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

Accepted Answer

A rare scale color in fish becomes more common because predators avoid unfamiliar prey.

Question 16

Which of the following would most likely increase genetic diversity within a population?

Accepted Answer

Migration from other populations

Question 17

Which of the following is NOT a mechanism that leads to evolution in populations?

Accepted Answer

Random mating

Question 18

If a population is not in Hardy-Weinberg equilibrium, what does this indicate?

Accepted Answer

The population is evolving and allele/genotype frequencies are changing.

Question 19

Which of the following best describes balancing selection?

Accepted Answer

Selection that maintains two or more alleles in a population over many generations.

Evolution of Populations: Population Genetics and Mechanisms of Evolution

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