Q: If the allele frequency for a beak length gene is $$ p = 0.4 $$ for allele A1 and $$ q = 0.6 $$ for allele A2, what is the expected proportion of heterozygotes under Hardy-Weinberg equilibrium?

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

Question 1

A population of birds exhibits the distribution of relative fitness versus beak length shown in the graph. Which type of natural selection is most likely occurring in this population?

Accepted Answer

Stabilizing selection

Question 2

Based on the graph, what would you expect to happen to the variation in beak length in this bird population over several generations?

Accepted Answer

Variation in beak length will decrease, with most individuals having intermediate beak lengths.

Question 3

If the mean beak length in the population is 35 mm, and the trait is heritable, what is the most likely outcome for the mean beak length after several generations of selection as shown in the graph?

Accepted Answer

The mean beak length will remain close to 35 mm.

Question 4

Suppose a mutation arises that causes some birds to have beak lengths of 42 mm. Based on the fitness curve shown, what is the likely fate of this mutation in the population?

Accepted Answer

The mutation will likely be eliminated due to low fitness.

Question 5

If environmental conditions change and seeds become larger and harder, causing birds with longer beaks to have higher fitness, how would the fitness curve change?

Accepted Answer

The fitness curve would shift to favor longer beaks, indicating directional selection.

Question 6

Given the fitness curve, which equation would you use to predict the proportion of individuals with a specific genotype under Hardy-Weinberg equilibrium?

Accepted Answer

$$ p^2$ + 2pq + q^2$ = 1 $$

Question 7

If the population is not in Hardy-Weinberg equilibrium, which of the following could explain the observed deviation?

Accepted Answer

Any of these mechanisms could explain the deviation.

Question 8

If the allele frequency for a beak length gene is $$ p = 0.4 $$ for allele A1 and $$ q = 0.6 $$ for allele A2, what is the expected proportion of heterozygotes under Hardy-Weinberg equilibrium?

Accepted Answer

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

Question 9

If inbreeding occurs in this population, what would you expect to happen to the proportion of heterozygotes?

Accepted Answer

The proportion of heterozygotes will decrease.

Question 10

If a population of birds with the fitness curve shown is reduced to only 10 individuals due to a natural disaster, which evolutionary mechanism will have the greatest effect on allele frequencies?

Accepted Answer

Genetic drift

Question 11

If the beak length trait is not heritable, what will happen to the population's response to selection as shown in the fitness curve?

Accepted Answer

The population will not evolve in response to selection.

Question 12

Suppose the population is at Hardy-Weinberg equilibrium and the frequency of the A1A1 genotype is $$ 0.25 . $$What is the frequency of the A1 allele?

Accepted Answer

$$ \sqrt{0.25} = 0.5 $$

Question 13

If a mutation causes a change in beak length, which of the following best describes the effect of mutation on evolution?

Accepted Answer

Mutation generates new alleles and increases genetic variation.

Question 14

If the environment changes and the fitness curve becomes bimodal, favoring both short and long beaks, which type of selection is occurring?

Accepted Answer

Disruptive selection

Question 15

If gene flow occurs between two populations of birds with different average beak lengths, what is the most likely effect on genetic diversity?

Accepted Answer

Genetic diversity will increase in both populations.

Question 16

If the fitness curve shown is due to environmental factors, but the trait is not genetically based, what is the most likely outcome for the population?

Accepted Answer

The population will not evolve, because the trait is not heritable.

Question 17

If the population is experiencing stabilizing selection as shown in the graph, which statement best describes the effect on genetic diversity?

Accepted Answer

Genetic diversity will decrease as extreme phenotypes are eliminated.

Question 18

If a population is in Hardy-Weinberg equilibrium, which equation describes the expected genotype frequencies?

Accepted Answer

$$ p^2$ $$ for homozygote A1A1, $$ 2pq $$ for heterozygote A1A2, $$ q^2$ $$ for homozygote A2A2

Question 19

If the population is very small and a rare allele is lost due to chance, which mechanism of evolution is responsible?

Accepted Answer

Genetic drift

Question 20

If the fitness curve shown is observed in a population, but the environment suddenly changes to favor longer beaks, what type of selection would you expect to occur?

Accepted Answer

Directional selection

Study Guide: Mechanisms of Evolution and Hardy-Weinberg Equilibrium

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