Question 1

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 results in a decrease in the fitness of a population due to the expression of recessive deleterious alleles, but it does not change the frequencies of those alleles. Evolution requires a change in allele frequencies over time, so inbreeding depression alone cannot cause evolution.

Question 2

Given the information about the number of individuals of specific genotypes in the table above,what can you infer?
A)A₂ is the dominant allele.
B)The relative amounts of each allele.
C)The phenotype of the individuals with each genotype.
D)The phenotype of A₁ is likely disadvantageous.

Accepted Answer

The table provides information about the number of individuals with each genotype, which allows us to infer the relative amounts of each allele. We can see that there are more individuals with the A₂A₂ genotype than any other genotype, indicating that the A₂ allele is likely more common in the population. However, we cannot determine which allele is dominant or recessive based on this information alone.

Answer: C
 The table does not provide information about the phenotype of individuals with each genotype, so we cannot make any inferences about this.

Answer: D
 The table does not provide any information about the fitness or advantage of any genotype, so we cannot make any inferences about whether the A₁ allele is disadvantageous.

Question 3

Given the information above,what is the frequency of individuals with the A₁A₁ genotype?
A)0)1
B)0)15
C)0)2
D)0)3
E)0)4

Accepted Answer

The frequency of individuals with the A₁A₁ genotype is 0.1. This is because the frequency of the A₁ allele is 0.5, and the frequency of the A₁A₁ genotype is equal to the square of the frequency of the A₁ allele.

Question 4

Which of the following is true?
A)Hardy-Weinberg can be used to examine only 1 gene at a time.
B)Hardy-Weinberg considers an organism's entire genotype (all genes).
C)Hardy-Weinberg can be used to examine more than 1 gene at a time.

Accepted Answer

Hardy-Weinberg equilibrium typically examines the allele frequencies of a single gene in a population to determine if evolution is occurring at that locus.

Question 5

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 6

Figure 25.4 
-Male turkeys have a snood,a flap of skin that hangs across their beak.Snood length is negatively correlated with parasite load (e.g.,males with longer snoods have fewer parasites),and females prefer to mate with long-snooded males.This is an example of
A)the fundamental asymmetry of sex.
B)sexual selection via female choice.
C)sexual selection via male-male competition.
D)a genetic marker.

Accepted Answer

The presence of a snood is a male secondary sexual characteristic that is subject to female choice, making this an example of sexual selection via female choice. Females prefer to mate with males that have longer snoods, which is likely due to the snood size being an indicator of male quality (i.e., males with long snoods may be healthier and have fewer parasites). This preference for longer snood length is an important factor in driving the evolution of this trait in male turkeys.

Question 7

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 each in 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

The small number of breeding individuals in each generation, 4 males and 4 females, likely contributed to the high percentage (73%) of populations with only one allele for the bristle morphology gene. Allowing 10 males and 10 females to breed would increase genetic diversity, making it less likely for a single allele to become fixed in the population. Therefore, we would expect less than 73% of populations to have only one allele present.

Question 8

Figure 25.4 
-This chapter's essay explains that the membrane protein involved in cystic fibrosis confers resistance to typhoid fever.Imagine that a drug-resistant form of typhoid fever becomes common worldwide,killing a significant proportion of the human population over a period of several decades.Which of the following would you expect to observe in the world population during this period?
A)no change in the frequency of cystic fibrosis
B)decrease in the frequency of cystic fibrosis
C)increase in the frequency of cystic fibrosis

Accepted Answer

Since the membrane protein involved in cystic fibrosis confers resistance to typhoid fever, individuals with cystic fibrosis would have a selective advantage and be more likely to survive the typhoid fever outbreak. As a result, the frequency of cystic fibrosis in the population would increase over time.

Question 9

Two frog populations (same species)living in two neighboring lakes sing slightly different courtship songs.Predict what likely happens to the songs of the two frog populations after increased irrigation makes the land between the two lakes wetter.Females prefer loud frogs to quieter frogs,but do not distinguish between the two slightly different songs.Assume that courtship song differences have a genetic basis.
A)The songs become more similar to each other.
B)The songs become more different from each other.
C)There is no change in the frog courtship songs of the two lakes.

Accepted Answer

Increased irrigation will make it easier for the two frog populations to come into contact with each other. As female frogs prefer loud males, there will be a selective pressure for both populations to become louder. As the courtship song differences have a genetic basis, it is likely that the genes responsible for producing louder songs will become more common in both populations. This will lead to the two populations' courtship songs becoming more similar to each other over time.

Question 10

Mutation is the only evolutionary mechanism that
A)does little to change allele frequencies on its own.
B)always causes decreased fitness.
C)is more important in eukaryotes than in prokaryotes.
D)is not mentioned by the Hardy-Weinberg model.
E)has no effect on genetic variation.

Accepted Answer

While mutation introduces new genetic variation, it is often a relatively slow process and alone does not typically cause significant changes in allele frequencies within a population. Other evolutionary mechanisms, such as natural selection, genetic drift, and gene flow, often have more significant impacts on the genetic makeup of populations.

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

Since species A has higher reproductive success, sexual selection is likely to be stronger in that species. Therefore, we would expect species A to exhibit greater sexual dimorphism compared to species B.

Question 12

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

The earthquake decimating the ground-squirrel population would result in a genetic bottleneck, where only a small subset of the initial population survive and reproduce, limiting the genetic diversity of the population. The fact that the surviving population has broader stripes on average suggests that the trait for broadness of stripes was more prevalent in the surviving individuals, potentially due to chance or selective pressures during the bottleneck event. However, there is not enough information provided to determine if this is directional or disruptive selection. A founder event would occur if a small subset of a population established a new population in a different location. Gene flow would occur if genetic material was exchanged between two populations.

Question 13

In some jacana species,males take care of the eggs and young,and females compete for territories and males against one another.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 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

Based on the information provided, male jacana fitness is primarily limited by their ability to take care of eggs and raise young (statement 1), and variation in reproductive success should be greater in female jacanas than in males (statement 4). This is because female jacanas compete for territories, and males take care of the young, so male reproductive success is more dependent on their ability to perform parental care duties, while female reproductive success is more dependent on their ability to secure a good territory and mate with high-quality males. Statement 2 is not necessarily true, as the number of mates a female has may not be the primary limiting factor for her reproductive success. Statement 3 may also not be true, as variation in reproductive success may be greater in females due to their territorial competition. Statement 5 is not supported by the information given.

Question 14

In 1986,a nuclear power accident in Chernobyl,USSR (now the 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)Mutation by itself led to 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

The high radiation levels from the nuclear power accident likely caused mutations in the rodent populations, which increased genetic variation. This increased variation may have allowed some individuals to survive and reproduce in the new environment. Over time, natural selection could act on this genetic variation, potentially leading to adaptation to the new conditions.

Question 15

If an allele is found at a frequency of 0.8 in a population that is in Hardy-Weinberg equilibrium,and an individual is heterozygous for that allele,what is the probability they will pass on that allele to their offspring?
A)0)8
B)0)2
C)0)5
D)0)64

Accepted Answer

In a heterozygous individual, there is a 50% chance of passing on either allele to their offspring.

Question 16

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 between two populations will result in a decreased genetic difference between the two populations as there will be more movement of genes between the populations. This is because gene flow involves the movement of individuals or gametes from one population to another, which can introduce new genes into a population or increase the frequency of existing genes. Therefore, over time, gene flow will lead to increased similarity between populations.

Question 17

The frequency of theB₁ allele (for an autosomal gene)in a population that is in Hardy-Weinberg equilibrium is 0.2 and the frequency of the B₂ allele is 0.8.The phenotype of allele B₁ is dominant to that of B₂.If females make up exactly half of the population,what is the frequency of the B₁ allele in the female population alone?
A)0)1
B)0)2
C)0)4
D)0)8

Accepted Answer

Since the population is in Hardy-Weinberg equilibrium, the frequency of alleles does not change in each generation. Therefore, the frequency of the B₁ allele is still 0.2 in both males and females. The fact that females make up exactly half of the population does not affect the frequency of alleles. Thus, the frequency of the B₁ allele in the female population alone is also 0.2.

Question 18

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 19

Which of the following describes what we should expect when a population is in Hardy-Weinberg genetic equilibrium?
A)a sexually reproducing population that is increasing in size
B)an asexually reproducing population that is increasing in size
C)a sexually reproducing population that is not evolving
D)an asexually reproducing population that is not evolving
E)a sexually reproducing population that is evolving.

Accepted Answer

In Hardy-Weinberg equilibrium, the allele frequencies remain constant over generations, indicating that the population is not evolving. This equilibrium applies to sexually reproducing populations, not asexually reproducing populations. The population size is not relevant to the equilibrium.

Question 20

Given the information above,what is the frequency of the A₂ allele in this population?
A)0)75
B)0)8
C)0)85
D)0)875
E)0)9

Accepted Answer

The answer of Given the information above,what is the frequency...

Quiz 25: Evolutionary Processes

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

Given the information about the number of individuals of specific genotypes in the table above,what can you infer?

Given the information above,what is the frequency of individuals with the A₁A₁ genotype?

Which of the following is true?

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

Figure 25.4 -Male turkeys have a snood,a flap of skin that hangs across their beak.Snood length is negatively correlated with parasite load (e.g.,males with longer snoods have fewer parasites) ,and females prefer to mate with long-snooded males.This is an example of

Mutation is the only evolutionary mechanism that

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?

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?

If an allele is found at a frequency of 0.8 in a population that is in Hardy-Weinberg equilibrium,and an individual is heterozygous for that allele,what is the probability they will pass on that allele to their offspring?

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 of the following describes what we should expect when a population is in Hardy-Weinberg genetic equilibrium?

Given the information above,what is the frequency of the A₂ allele in this population?