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?

$$f(r) = \frac{2 \times 16 + 48}{2 \times 100} = \frac{32 + 48}{200} = \frac{80}{200} = 0.4$$

Q: In a population in Hardy-Weinberg equilibrium, the frequency of allele A is $$p = 0.7$$ and the frequency of allele a is $$q = 0.3. $$What is the expected frequency of heterozygotes (Aa)?

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

Q: In a certain African population, 9% of individuals have sickle cell disease (homozygous recessive, $$q^2 = 0.09$). What percentage of the population is expected to be malaria resistant (heterozygotes)?

$$2pq = 2 \times 0.7 \times 0.3 = 0.42 or 42$$%

Question 1

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

Accepted Answer

Genetic variation allows individuals to adapt to changing environments, providing raw material for natural selection to act upon.

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?

Accepted Answer

$$f(r) = \frac{2 	imes 16 + 48}{2 	imes 100} = \frac{32 + 48}{200} = \frac{80}{200} = 0.4$$

Question 3

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

Accepted Answer

Natural selection is acting on the population.

Question 4

In a population in Hardy-Weinberg equilibrium, the frequency of allele A is $$p = 0.7$$ and the frequency of allele a is $$q = 0.3. $$What is the expected frequency of heterozygotes (Aa)?

Accepted Answer

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

Question 5

Which scenario best illustrates genetic drift?

Accepted Answer

A small group of birds is blown by a storm to a new island, and their allele frequencies differ from the original population.

Question 6

Which pattern of natural selection is most likely responsible for the increase in frequency of antibiotic-resistant bacteria after the introduction of a new antibiotic?

Accepted Answer

Directional selection

Question 7

A population of birds has a wide range of beak sizes. Over time, only birds with very large or very small beaks survive, while those with intermediate beak sizes are selected against. What type of selection is this?

Accepted Answer

Disruptive selection

Question 8

In a certain African population, 9% of individuals have sickle cell disease (homozygous recessive, $$q^2 = 0.09$). What percentage of the population is expected to be malaria resistant (heterozygotes)?

Accepted Answer

$$2pq = 2 	imes 0.7 	imes 0.3 = 0.42 or 42$$%

Question 9

Which of the following best describes the founder effect?

Accepted Answer

A small group separates from a larger population, leading to different allele frequencies and reduced genetic variation.

Question 10

Which of the following is an example of frequency-dependent selection?

Accepted Answer

A rare coloration in a fish species confers a survival advantage because predators are less likely to recognize it.

Question 11

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

Accepted Answer

Migration (gene flow) from another population

Question 12

Which of the following is a key difference between intrasexual and intersexual selection?

Accepted Answer

Intrasexual selection involves competition among members of the same sex, while intersexual selection involves mate choice by the opposite sex.

Question 13

A population of 500 individuals is reduced to 20 by a natural disaster. The surviving population has different allele frequencies than the original. What is this an example of?

Accepted Answer

Bottleneck effect

Question 14

Which of the following would indicate that a population is NOT in Hardy-Weinberg equilibrium?

Accepted Answer

Observed genotype frequencies differ significantly from those predicted by $$p^2 + 2pq$$ + $$q^2 = 1$

Question 15

Which of the following is most likely to cause a rapid change in allele frequencies in a small population, regardless of fitness?

Accepted Answer

Genetic drift

Question 16

If the frequency of the dominant allele $$E$$ for wet earwax is $$0.8$$, what is the expected frequency of individuals with dry earwax (homozygous recessive, $$ee) in a $$population in Hardy-Weinberg equilibrium?

Accepted Answer

$$q^2 = (1$$ - $$0.8)^2 = 0.04$

Question 17

Which of the following is an example of stabilizing selection?

Accepted Answer

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

Question 18

Which of the following best describes a monomorphic gene?

Accepted Answer

A gene for which only one allele exists in a population.

Question 19

Which evolutionary process is most likely to reduce differences in allele frequencies between two populations?

Accepted Answer

Migration (gene flow)

Question 20

Which of the following is a direct measure of an individual's fitness in evolutionary terms?

Accepted Answer

The number of offspring that survive to reproduce in the next generation.

Evolution of Populations: Population Genetics and Mechanisms of Evolution

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