Question 1

Which of the following is the most predictable outcome of increased gene flow between two populations?
A)lower average fitness in both populations
B)higher average fitness in both populations
C)increased genetic difference between the two populations
D)decreased genetic difference between the two populations
E)increased genetic drift

Accepted Answer

Increased gene flow typically leads to decreased genetic difference between the two populations as there is an increase in the exchange of genetic material. This can ultimately result in the fusion of the two populations into a single population with a more homogeneous genetic makeup.

Question 2

In Kerr and Wright's experiment with 96 fruit-fly populations,only 4 males and 4 females bred in each generation.After 16 generations,73% of their populations had only one allele present for the bristle morphology gene.Which of the following would you expect to occur if they allowed 10 males and 10 females to breed in each generation?
A)About 73% of the populations would have only one allele for the bristle morphology gene.
B)More than 73% of the populations would have only one allele present.
C)Less than 73% of the populations would have only one allele present.
D)All of the populations would have only one allele present.

Accepted Answer

Increasing the number of breeding individuals should increase genetic diversity within the population, making it less likely for a single allele to become fixed. Therefore, we would expect less than 73% of populations to have only one allele present after allowing 10 males and 10 females to breed in each generation.

Question 3

In 1986 a nuclear power accident in Chernobyl,USSR (now Ukraine),led to high radiation levels for miles surrounding the plant.The high levels of radiation caused elevated mutation rates in the surviving organisms,and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since.Based on your understanding of evolutionary mechanisms,which of the following most likely occurred in the rodent populations following the accident?
A)Mutations caused major changes in rodent physiology over time.
B)Mutation led to increased genetic variation.
C)Mutation caused genetic drift and decreased fitness.
D)Mutation caused the fixation of new alleles.

Accepted Answer

Mutations can lead to increased genetic variation, which can then be acted upon by natural selection. In the case of the Chernobyl rodent populations, the high levels of radiation caused elevated mutation rates, which likely resulted in increased genetic variation within the populations. This increased genetic variation could have allowed certain individuals to be better adapted to the new environmental conditions caused by the radiation, and therefore more likely to survive and reproduce.

Question 4

A beneficial point mutation occurs in a plant ovule,which is fertilized.The seed matures,falls to the ground,and starts to grow.Is the plant's population likely to show evolutionary change as a result of this mutation? Why or why not?

Accepted Answer

The answer of A beneficial point mutation occurs in a...

Question 5

A rare species of newt is being studied by a young evolutionary biologist.She observes that female newts lay unusually large yolky eggs,but they abandon their nests as soon as the eggs are laid.Males,on the other hand,defend the territory around the nest and regularly bring the baby newts insects to feed on.The males also sleep with the babies to keep them warmer during cool nights.Which of the following statements is MOST LIKELY to be true of these newts?
A)The males are smaller than the females.
B)The males have lots of bright coloring on their skin to attract females.
C)The females are not choosy about which males to mate with.
D)The males are choosy about which females to mate with.
E)Males have far more offspring than females.

Accepted Answer

In species where males invest heavily in parental care, they tend to be choosier about mates because their investment in offspring is high.

Question 6

In some jacana species,males take care of the eggs and young,and females compete among themselves for territories that contain one to several males.Female jacanas are significantly larger than males.Which of these statements would you predict to be true of this bird species?
1)Male jacana fitness is primarily limited by ability to take care of eggs and raise young.
2)Female jacana fitness is limited by the number of males in her territory with which a female mates.
3)Variation in reproductive success should be greater in male jacanas than in females.
4)Variation in reproductive success should be greater in female jacanas than in males.
5)Males and females have equal variation in reproductive success.
A)1 and 3
B)2 and 4
C)1,2,and 3
D)1,2,and 4
E)5

Accepted Answer

Male jacana fitness is primarily limited by their ability to take care of eggs and raise young, as this is their primary responsibility. Female jacana fitness, on the other hand, is limited by the number of males in their territory as they compete for access to males to mate with. This leads to greater variation in reproductive success for females than males. Therefore, options 1, 2, and 4 are correct, making option D the best choice. Option 5 is incorrect as it suggests equal variation in reproductive success, which is not the case. Option 3 is also incorrect as it suggests that variation in reproductive success is greater in males, which is not supported by the information given in the passage.

Question 7

Which sex typically has more extreme sex-selected characteristics:
 males or females? Why? Give an example.

Accepted Answer

The answer of Which sex typically has more extreme sex-selected...

Question 8

An earthquake decimates a ground-squirrel population.The surviving population happens to have broader stripes on average than the initial population.If broadness of stripes is genetically determined,what effect has the ground-squirrel population experienced during the earthquake?
A)directional selection
B)disruptive selection
C)a founder event
D)a genetic bottleneck
E)gene flow

Accepted Answer

A genetic bottleneck occurs when a population undergoes a drastic decrease in size, leading to a reduction in genetic diversity. In this case, the earthquake caused a decrease in the ground-squirrel population, resulting in a smaller surviving population with broader stripes. This is an example of genetic drift, which can lead to changes in the frequency of alleles in a population, such as the allele for broader stripes becoming more common.

Question 9

Two frog populations (same species)living in two neighboring lakes sing slightly different courtship songs.Increased irrigation makes the land between the two lakes wetter,allowing frogs to expand their ranges to the area between the lakes.Females in both populations prefer loud frogs to quieter frogs,but do not distinguish between the two slightly different songs.Assuming that courtship song differences have a genetic basis,predict what will likely happen to the songs of the two frog populations.
A)The songs become more similar to each other.
B)Males will become louder.
C)Disruptive selection will cause the songs to differentiate even more.
D)Genetic drift will cause the songs to differentiate even more.
E)You cannot predict a change in the courtship songs at the two lakes.

Accepted Answer

The increased availability of habitat between the two lakes will allow for more opportunities for mating between individuals from the two populations. Since females prefer loudness in males rather than song differentiation, individuals with the loudest songs are likely to have more breeding success. Therefore, over time, the genetic makeup of the population is likely to shift towards those with the loudest songs, resulting in a convergence of the two populations towards a common courtship song type. This process is called gene flow, which leads to the reduction of genetic differences between populations.

Question 10

Why doesn't inbreeding depression,by itself,cause evolution?
A)It decreases the population's average fitness.
B)It limits gene flow.
C)It does not change the population's allele frequencies.
D)It increases homozygosity.
E)It violates the Hardy-Weinberg assumptions.

Accepted Answer

Inbreeding depression, which is the reduction in fitness of a population due to the breeding of closely related individuals, does not cause evolution on its own because it does not change the overall allele frequencies in the population. Evolution requires changes in allele frequencies over time, either through natural selection, genetic drift, mutation, or gene flow. Inbreeding depression may reduce the population's fitness, but it does not necessarily lead to changes in the genetic makeup of the population. Therefore, choice C is the best answer.

Question 11

Figure 25.4 
-Refer to Figure 25.4.Male reproductive success,measured as the number of offspring surviving to adulthood (pupating),is found for two closely related beetle species and graphed above.Which of these statements would you expect to be true of sexual dimorphism in the two species?
A)Species A should have greater sexual dimorphism than species B.
B)Species B should have greater sexual dimorphism than species A.
C)Species A and B should have about equal amounts of sexual dimorphism.
D)Neither species should show any sexual dimorphism.

Accepted Answer

The graph shows that species A has a much wider range of reproductive success, with some males producing a lot more offspring than others. This suggests that there may be greater sexual selection on males in species A, leading to greater sexual dimorphism compared to species B.

Question 12

Mutation is the only evolutionary mechanism that _____.
A)does little to change allele frequencies
B)decreases fitness
C)is more important in eukaryotes than in prokaryotes
D)happens in all populations
E)has no effect on genetic variation

Accepted Answer

Mutation typically introduces new alleles into a population at a low rate, so it does little to change allele frequencies compared to other mechanisms like natural selection or genetic drift.

Quiz 25: Evolutionary Processes

Which of the following is the most predictable outcome of increased gene flow between two populations?

A beneficial point mutation occurs in a plant ovule,which is fertilized.The seed matures,falls to the ground,and starts to grow.Is the plant's population likely to show evolutionary change as a result of this mutation? Why or why not?

Which sex typically has more extreme sex-selected characteristics: males or females? Why? Give an example.

An earthquake decimates a ground-squirrel population.The surviving population happens to have broader stripes on average than the initial population.If broadness of stripes is genetically determined,what effect has the ground-squirrel population experienced during the earthquake?

Why doesn't inbreeding depression,by itself,cause evolution?

Figure 25.4 -Refer to Figure 25.4.Male reproductive success,measured as the number of offspring surviving to adulthood (pupating) ,is found for two closely related beetle species and graphed above.Which of these statements would you expect to be true of sexual dimorphism in the two species?

Mutation is the only evolutionary mechanism that _____.