05-lrq: Mechanisms Of Evolution

1. A population is composed of individuals of the following genotypes: 200 GG, 150 Gg, and 150 gg. If the G and g alleles are the only ones found at this locus, what is the frequency of the G allele in this population?

D. 0.75

A. 0.45

C. 0.65

B.0.55

To calculate the frequency of the G allele in the population, we first need to add up the total number of alleles. This would be 200(GG) + 150(Gg) + 150(gg) = 500 alleles. The frequency of the G allele is calculated by adding up the G alleles from GG and Gg genotypes and dividing by the total number of alleles. This gives us (200 + 150)/500 = 350/500 = 0.7. Therefore, the frequency of the G allele in this population is 0.7, which is closest to option B (0.55).

Explanation

To calculate the frequency of the G allele in the population, we first need to add up the total number of alleles. This would be 200(GG) + 150(Gg) + 150(gg) = 500 alleles. The frequency of the G allele is calculated by adding up the G alleles from GG and Gg genotypes and dividing by the total number of alleles. This gives us (200 + 150)/500 = 350/500 = 0.7. Therefore, the frequency of the G allele in this population is 0.7, which is closest to option B (0.55).

2. Suppose you are studying a population of beetles where body color is determined by a single locus: H confers red color and h confers white, with H incompletely dominant over h such that heterozygotes are pink. You also know in a population of 1,000 individuals, there are 360 red individuals 480 pink individuals. What are the frequencies of the H and h allele, respectively, in this population?

0.7 and 0.3

C. 0.6 and 0.4

0.3 and 0.7

0.8 and 0.2

In this scenario, we have 360 red individuals, 480 pink individuals, and 1,000 total individuals in the population. The red individuals are homozygous for the H allele, the pink individuals are heterozygous (Hh), and we can assume the white individuals are homozygous for the h allele. From this information, we can calculate the frequency of the H and h alleles in the population using Hardy-Weinberg equilibrium calculations.

Explanation

In this scenario, we have 360 red individuals, 480 pink individuals, and 1,000 total individuals in the population. The red individuals are homozygous for the H allele, the pink individuals are heterozygous (Hh), and we can assume the white individuals are homozygous for the h allele. From this information, we can calculate the frequency of the H and h alleles in the population using Hardy-Weinberg equilibrium calculations.

3. Which of these conditions must be TRUE for populations to evolve by natural selection?

III only

I and II only

I only

B.II only

In order for populations to evolve by natural selection, heritable variation in one or more traits must influence the reproductive success of the bearers. This makes option II the correct choice. Option I is incorrect because populations can evolve by natural selection regardless of whether they reproduce sexually or asexually. Option III is incorrect because individuals do not pass on all traits they acquire during their lifetime, as only traits that are heritable and influence reproductive success affect evolution by natural selection. Option I and II is incorrect because sexual reproduction is not a requirement for evolution by natural selection.

Explanation

In order for populations to evolve by natural selection, heritable variation in one or more traits must influence the reproductive success of the bearers. This makes option II the correct choice. Option I is incorrect because populations can evolve by natural selection regardless of whether they reproduce sexually or asexually. Option III is incorrect because individuals do not pass on all traits they acquire during their lifetime, as only traits that are heritable and influence reproductive success affect evolution by natural selection. Option I and II is incorrect because sexual reproduction is not a requirement for evolution by natural selection.

4. Both genetic drift and natural selection are forces of evolution. However, an identifiable difference between the effect of drift and the effect of selection is:

A.drift causes random changes in allele frequencies while the allele frequency changes due to selection are never random.

C. drift only affects alleles that are recessive while selection can change the frequencies of both recessive and dominant alleles.

B. drift always causes allele frequencies to decrease while selection always causes them to increase.

D. drift leads to an increase in the genetic diversity within populations while selection decreases genetic diversity.

The correct answer is A because genetic drift causes random changes in allele frequencies while the allele frequency changes due to selection are never random. This is a key difference between the two forces of evolution.

Explanation

The correct answer is A because genetic drift causes random changes in allele frequencies while the allele frequency changes due to selection are never random. This is a key difference between the two forces of evolution.

5. In a large population, the frequency of an allele changes smoothly and steadily from 60% to 20% over 100 generations. From this change, one can most logically assume that

A. the allele is dominant.

B. the allele is recessive.

C.the allele reduces the fitness of the bearer.

D. random processes have changed allele frequencies.

The correct answer is C. If the frequency of an allele decreases steadily over generations, it indicates that individuals carrying that allele may have reduced fitness, meaning they are less likely to survive and reproduce. This can lead to a decrease in the allele frequency in the population.

Explanation

The correct answer is C. If the frequency of an allele decreases steadily over generations, it indicates that individuals carrying that allele may have reduced fitness, meaning they are less likely to survive and reproduce. This can lead to a decrease in the allele frequency in the population.

6. Based on the information provided, which of the following terms applies to the situation where the frequency of the A allele increases steadily over several generations?

B. II only

C. III only

A. I only

D.I and IIz

7. Which of the following statements regarding evolution by natural selection is false?

Natural selection is only one way in which populations can evolve.

B Natural selection is a random process

Natural selection is a process that produces adaptations.

Natural selection can change the frequencies of alleles in gene pools.

Natural selection is not a random process; it is a non-random process where organisms with favorable traits are more likely to survive and reproduce.

Explanation

Natural selection is not a random process; it is a non-random process where organisms with favorable traits are more likely to survive and reproduce.

8. In a certain population, there are two alleles (T and t) at a locus with the frequency of the T allele = 0.4. You collect the following information from this population: 300 TT individuals, 200 Tt individuals, 500 tt individuals. Is there any evidence that this population is evolving?

C. Yes; there are fewer Tt individuals than predicted in the absence of evolution.

Yes; there are fewer tt individuals than predicted in the absence of evolution.

Yes; there are fewer TT individuals than predicted in the absence of evolution.

No.

The correct answer is C. It indicates evolving population when the actual quantities of genotypes differ from those expected based on the initial allele frequencies. Here, the frequency of T allele is 0.4, which should result in approximately 240 TT individuals, 320 Tt individuals, and 240 tt individuals in the absence of evolution. The observed count of Tt individuals (200) is significantly lower than expected, suggesting evolution is occurring in the population.

Explanation

The correct answer is C. It indicates evolving population when the actual quantities of genotypes differ from those expected based on the initial allele frequencies. Here, the frequency of T allele is 0.4, which should result in approximately 240 TT individuals, 320 Tt individuals, and 240 tt individuals in the absence of evolution. The observed count of Tt individuals (200) is significantly lower than expected, suggesting evolution is occurring in the population.

9. You have been studying a small (over the course of your study this population has stayed at about 20 individuals each generation), isolated population of field mice for many generations. You have determined that there is a single locus with two alleles that controls coat color in this species: GG individuals are black, Gg individuals are dark brown, and gg individuals are tan. You have also found that tan individuals are the most obvious to predators and have the lowest relative fitness while the relative fitness of black individuals is the highest. In the current generation you have found that the population consists of only tan individuals. Which evolutionary force is most likely to have produced this recent change?

B.Genetic drift

C. Gene flow

D. Non-random mating

A. Natural selection

The correct answer is B. Genetic drift. In this scenario, the sudden presence of only tan individuals in a population that previously had a mix of coat colors suggests a random change in allele frequencies due to genetic drift, rather than natural selection, gene flow, or non-random mating.

Explanation

The correct answer is B. Genetic drift. In this scenario, the sudden presence of only tan individuals in a population that previously had a mix of coat colors suggests a random change in allele frequencies due to genetic drift, rather than natural selection, gene flow, or non-random mating.

10. Males competing with other males for the opportunity to mate with females is an example of _________; females selecting males based on phenotypic characteristics is an example of ___________.

C.intrasexual selection; intersexual selection

B. heterozygous selection; homozygous selection

D. kin selection; sexual selection

A. paternal selection; maternal selection

Intrasexual selection refers to competition between individuals of one sex, typically males in this case, for access to the opposite sex, while intersexual selection involves one sex, in this case females, selecting mates based on certain characteristics. The other options do not accurately represent the concepts described in the question.

Explanation

Intrasexual selection refers to competition between individuals of one sex, typically males in this case, for access to the opposite sex, while intersexual selection involves one sex, in this case females, selecting mates based on certain characteristics. The other options do not accurately represent the concepts described in the question.

11. Agronomists at the University of Illinois selected corn kernels with high oil content over 50 generations. They were eventually able to increase the average oil content by 10%. This is an example of

C. stabilizing selection

D. disruptive selection

A. sexual selection

B.directional selection.

Directional selection occurs when one extreme of a trait is favored over others in a population, leading to a shift in the average value of that trait in the population. In this case, the agronomists selecting corn kernels with high oil content over generations resulted in an increase in the average oil content, showcasing directional selection.

Explanation

Directional selection occurs when one extreme of a trait is favored over others in a population, leading to a shift in the average value of that trait in the population. In this case, the agronomists selecting corn kernels with high oil content over generations resulted in an increase in the average oil content, showcasing directional selection.

12. In the phenomenon known as a population bottleneck, _________ decreases as the __________ of a population is reduced.

B. genetic variability; mutation rate

A.genetic variability; size

D. heterozygosity; gene pool

C. gene flow; fitness

In a population bottleneck, the genetic variability decreases as the size of the population is reduced. This reduction in population size leads to a decrease in the variety of genes present within the population, which can have long-term effects on genetic diversity and adaptation.

Explanation

In a population bottleneck, the genetic variability decreases as the size of the population is reduced. This reduction in population size leads to a decrease in the variety of genes present within the population, which can have long-term effects on genetic diversity and adaptation.

13. In areas of Africa where malaria is common, humans that are homozygous for either the allele that confers sickle-cell anemia or homozygous for the normal have lower fitness than individuals that have one copy of each. This is an example of __________ advantage.

Homeothermic

B.heterozygote

Homozygote

Hemizygote

In this scenario, individuals with one copy of each allele (heterozygote) have a higher fitness due to their increased resistance to malaria compared to individuals who are homozygous for sickle-cell anemia or the normal allele.

Explanation

In this scenario, individuals with one copy of each allele (heterozygote) have a higher fitness due to their increased resistance to malaria compared to individuals who are homozygous for sickle-cell anemia or the normal allele.

14. In the absence of mutation, natural selection, gene flow, genetic drift, and non-random mating, the relative frequencies of alleles in a population will

C. decrease if the alleles are recessive.

A. fluctuate as long as no agent of evolution is operating.

D.remain constant throughout subsequent generations.

B. be invarient under all conditions.

The correct answer is that in the absence of the mentioned evolutionary agents, the relative frequencies of alleles in a population will remain constant throughout subsequent generations. This is because without these factors influencing allele frequencies, there is no mechanism for the frequencies to change over time.

Explanation

The correct answer is that in the absence of the mentioned evolutionary agents, the relative frequencies of alleles in a population will remain constant throughout subsequent generations. This is because without these factors influencing allele frequencies, there is no mechanism for the frequencies to change over time.

15. Under the conditions of a Hardy-Weinberg equilibrium for a gene with two alleles in a population of organisms, if the relative frequency of the recessive allele a is 0.4, what would be the expected relative frequency of heterozygous individuals (Aa)?

0.24

0.16

0.36

A.0.48

In a Hardy-Weinberg equilibrium, the frequency of heterozygous individuals (Aa) can be calculated using the formula 2pq, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. Given that the relative frequency of the recessive allele a is 0.4, the frequency of the dominant allele A would be (1 - 0.4) = 0.6. Therefore, 2 * 0.6 * 0.4 = 0.48, which is the expected relative frequency of heterozygous individuals (Aa).

Explanation

In a Hardy-Weinberg equilibrium, the frequency of heterozygous individuals (Aa) can be calculated using the formula 2pq, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. Given that the relative frequency of the recessive allele a is 0.4, the frequency of the dominant allele A would be (1 - 0.4) = 0.6. Therefore, 2 * 0.6 * 0.4 = 0.48, which is the expected relative frequency of heterozygous individuals (Aa).

16. Inbreeding within a population can be expected to

C. increase the chance of deleterious alleles being expressed in offspring.

B. decrease the proportion of the population that is heterozygous.

A. increase the proportion of the population that is homozygous.

D.All of the above are likely outcomes of inbreeding.

Inbreeding leads to increased homozygosity, decreased heterozygosity, and increased expression of deleterious alleles in offspring due to the increased likelihood of inheriting two copies of the same deleterious allele from a common ancestor.

Explanation

Inbreeding leads to increased homozygosity, decreased heterozygosity, and increased expression of deleterious alleles in offspring due to the increased likelihood of inheriting two copies of the same deleterious allele from a common ancestor.

17. A genetic polymorphism can be expected to remain in a population when

C. gene flow is high and both alleles are continually being added to the population.

B. the heterozygote has higher fitness than either of the homozygotes.

D.All of the above.

A. both alleles at a locus are neutral in a large population.

In order for a genetic polymorphism to persist in a population, any of the three conditions mentioned in the options (neutral alleles, heterozygote advantage, and high gene flow) can contribute to its maintenance.

Explanation

In order for a genetic polymorphism to persist in a population, any of the three conditions mentioned in the options (neutral alleles, heterozygote advantage, and high gene flow) can contribute to its maintenance.

18. A gene pool can best be described as the

C.total collection of genes in a population at a time.

B. total number of gene loci that co-occur in two species.

D. group of genes responsible for polygenic traits.

A. group of genes not described by the Hardy-Weinberg theorem.

The gene pool refers to the total collection of genes in a population at a particular time, representing the genetic diversity and variation within that population. It is not limited to specific gene loci, genes not described by the Hardy-Weinberg theorem, or genes responsible for polygenic traits.

Explanation

The gene pool refers to the total collection of genes in a population at a particular time, representing the genetic diversity and variation within that population. It is not limited to specific gene loci, genes not described by the Hardy-Weinberg theorem, or genes responsible for polygenic traits.

19. What is a major difference between evolution and natural selection?

C.Natural selection is one mechanism that can result in the process of evolution.

B. Evolution is a specific mechanism that can result in the general process of natural selection.

D. The difference is a matter of scale: natural selection produces small-scale changes in populations, while evolution produces large-scale ones.

A. There is no difference: natural selection and evolution are merely different terms for the same process.

While natural selection is a mechanism within the broader process of evolution, evolution encompasses a range of mechanisms beyond just natural selection. This distinction is important in understanding the various processes involved in species adaptation and change over time.

Explanation

While natural selection is a mechanism within the broader process of evolution, evolution encompasses a range of mechanisms beyond just natural selection. This distinction is important in understanding the various processes involved in species adaptation and change over time.

20. Natural selection is most closely associated with

Gene flow

Genetic drift

A.differential reproductive success.

Random mating

Natural selection is the process by which certain heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. Differential reproductive success refers to the idea that individuals with advantageous traits are more likely to pass on their genes to the next generation, resulting in the spread of those traits. Genetic drift, random mating, and gene flow are all important factors in evolution, but they are not as directly linked to natural selection as differential reproductive success.

Explanation

Natural selection is the process by which certain heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. Differential reproductive success refers to the idea that individuals with advantageous traits are more likely to pass on their genes to the next generation, resulting in the spread of those traits. Genetic drift, random mating, and gene flow are all important factors in evolution, but they are not as directly linked to natural selection as differential reproductive success.