Question 1

Which vegetable was produced from wild mustard, Brassica oleracea, through continued selection for larger stems and flowers?
A) Kale
B) Brussels sprouts
C) Cabbage
D) Cauliflower
E) Broccoli

Accepted Answer

Broccoli was developed from wild mustard, Brassica oleracea, through selective breeding for larger stems and flowers.

Question 2

Which phrase best describes natural selection?
A) The differential survival and reproduction of individuals
B) Chance variations in traits
C) The processes that lead individuals to resemble their parents
D) The potential for all species to increase rapidly in number
E) Individuals evolving in response to environmental change

Accepted Answer

Natural selection refers to the process by which certain organisms with advantageous traits survive and reproduce more successfully than others. This leads to a differential survival and reproduction of individuals, with those possessing favorable traits passing them on to their offspring.

Question 3

The graph shows the range of variation among population members for a trait determined by multiple genes.  Suppose that there were no genetic component to this trait.If this population were subject to stabilizing selection for several generations, which distributions would be most likely to result? Assume that the environment stayed the same. 
A) a
B) b
C) c
D) d
E) None of the above; there would be no change in the distribution.

Accepted Answer

E

Question 4

Suppose mutation and selection no longer occurred in a small, isolated population of nematodes.Which process would most likely continue operating, and what would be the most likely effect on the extent of genetic variation?
A) Gene flow would lead to an increase in genetic variation.
B) Gene flow would lead to a decrease in genetic variation.
C) Genetic drift would lead to an increase in genetic variation.
D) Genetic drift would lead to a decrease in genetic variation.
E) Genetic drift would operate but would have no effect on genetic variation.

Accepted Answer

If mutation and selection ceased to operate, genetic drift would become the primary driver of changes in the population's gene pool. Genetic drift is a random process that can cause the frequency of alleles to fluctuate rapidly over time, especially in small populations. This can result in some alleles being lost entirely while others become fixed, which would reduce genetic variation overall. Therefore, the most likely effect of genetic drift in this scenario would be a decrease in genetic variation.

Question 5

Yeast cells are sequenced periodically to examine them for new mutations.The table shows the results.  What is the approximate mutation rate per generation for strain A?
A) 3
B) 6
C) 14
D) 43
E) 59

Accepted Answer

The answer of Yeast cells are sequenced periodically to examine...

Question 6

Polydactyly (having more than five fingers on a hand) is much more common in some isolated human populations than it is elsewhere.This is most likely an example of a(n) _______, which is due to the evolutionary mechanism called _______.
A) founder effect; gene flow
B) founder effect; genetic drift
C) adaptation; gene flow
D) genetic ratchet; gene flow
E) genetic ratchet; genetic drift

Accepted Answer

The founder effect occurs when a small sample of a population establishes a new colony, resulting in a loss of genetic variation. Genetic drift is a mechanism of evolution that occurs when chance events cause random fluctuations in allele frequencies in a population. In this case, polydactyly is more common in isolated populations, suggesting that a small sample of ancestors carried the genetic trait that leads to polydactyly and passed it on to their descendants, leading to a higher frequency of the trait in these populations. This is an example of the founder effect in action. Therefore, the best answer is B: founder effect; genetic drift.

Question 7

The artificial selection experiments with bristle numbers in Drosophila illustrated which generality?
A) In such experiments, it is difficult to obtain individuals with traits that fall outside the range found in the original population.
B) Populations often contain considerable genetic variation upon which selection can operate.
C) Such experiments usually take thousands of generations to achieve their results.
D) Mutations occur to suit the needs of the population.
E) New species can be created via artificial selection.

Accepted Answer

The artificial selection experiments illustrated that populations often contain considerable genetic variation upon which selection can operate. This is because the selection experiments were successful in producing significant changes in bristle number within relatively few generations, indicating that genetic variation existed for this trait in the original population.

Question 8

If variation at a given locus has no effect on the phenotypes of individuals, which evolutionary process will still occur at that locus?
A) Genetic drift
B) Natural selection
C) Nonrandom mating
D) Purifying selection
E) Positive selection

Accepted Answer

Even if variation at a locus has no effect on phenotypes, genetic drift can still occur and result in changes in allele frequencies over time. Genetic drift is a random process that can impact small populations in particular, leading to the fixation of one allele or the loss of an allele from the population.

Question 9

Which two evolutionary processes would most likely act in opposite ways regarding their effects on the extent of genetic variation in a population?
A) Mutation and gene flow
B) Genetic drift and directional selection
C) Mutation and diversifying selection
D) Gene flow and diversifying selection
E) Mutation and directional selection

Accepted Answer

Mutation introduces new genetic variations, while directional selection tends to reduce genetic variation by favoring a specific trait.

Question 10

Different populations of mice that were previously isolated now experience gene flow.What is the most likely outcome after several generations?
A) The populations will become more genetically similar to one another.
B) The populations will become less genetically similar to one another.
C) The total amount of genetic variation across all of the populations will increase.
D) The total amount of genetic variation across all of the populations will decrease.
E) A founder effect will occur.

Accepted Answer

Gene flow is the movement of genes from one population to another. This can lead to an increase in genetic similarity between previously isolated populations, as genes mix and spread throughout the populations. Over several generations, this can result in a reduction in genetic differences between the populations.

Question 11

High-throughput sequencing reveals that ten new mutations have occurred in the coding regions of genes in an individual bat.If the coding regions of this bat comprise 100 million nucleotides per haploid genome, what is the mutation rate per nucleotide?
A) 5 per billion
B) 10 per billion
C) 50 per billion
D) 5 per million
E) 10 per million

Accepted Answer

The answer of High-throughput sequencing reveals that ten new mutations...

Question 12

What is the main difference between Darwin and Wallace with respect to their contributions to evolutionary biology?
A) Only Darwin had been a naturalist and had studied animals and plants in their natural settings.
B) Only Wallace had been a naturalist and had studied animals and plants in their natural settings.
C) Darwin presented more extensive evidence in support of evolution than Wallace.
D) Darwin developed a mathematical model of evolution.
E) Wallace developed a mathematical model of evolution.

Accepted Answer

Both Darwin and Wallace were naturalists who studied animals and plants in their natural settings. However, Darwin presented a much more extensive body of evidence in support of evolution than Wallace. Darwin had been collecting evidence and thinking about evolution for over 20 years before he published On the Origin of Species, whereas Wallace had been thinking about it for only a few years before independently arriving at similar conclusions. However, Wallace's own contributions to evolutionary theory were also significant and cannot be discounted.

Question 13

The haploid human genome contains about 3 billion bp.Given a mutation rate of 5 × 10^-⁹, how many new mutations would we expect on average in each diploid individual? A) 1 B) 3 C) 15 D) 30 E) 60

Accepted Answer

The mutation rate is given as $5 \times 10^{-8}$ per base pair. Since the haploid human genome contains about 3 billion base pairs (bp), a diploid genome would have about 6 billion bp. Multiplying the mutation rate by the number of base pairs in a diploid genome gives the expected number of new mutations per individual: $5 \times 10^{-8} \times 6 \times 10^9 = 300$. However, the correct interpretation of the mutation rate provided (considering the formatting might be misinterpreted) should lead to an expectation of around 30 new mutations per diploid genome per generation, aligning with current scientific understanding.

Question 14

Which statement about Darwin is true?
A) Even as a youth he recognized that life evolves.
B) He published his observations about evolution soon after the HMS Beagle arrived in England.
C) He recognized that animals on the Galápagos Islands were all identical to those on the mainland.
D) He had a keen interest in geology.
E) He was the first to present evidence that life has evolved.

Accepted Answer

Darwin had a keen interest in geology and his studies on rock formations and fossils helped him develop his theory of evolution.

Question 15

Due to various causes, including DDT poisoning, the population size of whooping cranes was reduced to about a dozen during the 1970s.The population size has since rebounded, and there are now hundreds of whooping cranes.Which feature would not be expected in the current populations of whooping cranes?
A) Very low levels of genetic variation
B) Very few heterozygous individuals
C) Differences from historical populations in terms of allele frequencies
D) Considerable genetic polymorphism
E) A bottleneck effect

Accepted Answer

Considerable genetic polymorphism would be expected in the current populations of whooping cranes. The rebound in population size would have resulted from the survival and reproduction of individuals with diverse genetic backgrounds, contributing to genetic polymorphism. Low levels of genetic variation (A), few heterozygous individuals (B), differences in allele frequencies (C), and a bottleneck effect (E) may have been expected in the current populations due to the historical population size reduction, which would have reduced genetic diversity.

Question 16

Which understanding do modern biologists have that Darwin did not have?
A) The tendency of individuals to resemble their parents
B) The common ancestry of species that exist today
C) The details of genetic inheritance
D) The operation of natural selection on changes in species over time
E) The greater similarity of species in temperate and tropical regions of South America than of species in temperate regions of South America and Europe

Accepted Answer

Modern biologists have a much more detailed understanding of genetic inheritance than Darwin did. Today's biologists are able to study genetic material and understand how specific traits are inherited and expressed, whereas Darwin was limited to observing the outward appearance and behavior of organisms.

Answer: B
 Darwin proposed the idea of common ancestry between species, but modern biologists have since been able to provide substantial evidence to support this theory through genetic and fossil evidence. Additionally, modern biologists have a better understanding of how species diverge and evolve over time through processes such as genetic drift, gene flow, and mutation.

Question 17

Two populations of raccoons are similar in most respects, but the population on the east side of a river is much smaller than that on the west side.There is little gene flow between the populations.Which statement about these populations is most accurate?
A) The population on the west side of the river should experience more fluctuations in allele frequency due to genetic drift.
B) The population on the east side of the river should experience more fluctuations in allele frequency due to genetic drift.
C) The population on the west side of the river should have more fluctuations in allele frequency because it will experience a higher mutation rate.
D) The population on the east side of the river should have more fluctuations in allele frequency because it will experience a higher mutation rate.
E) The populations should experience similar degrees of fluctuations in allele frequency because mutation and genetic drift should affect them in the same way.

Accepted Answer

The population on the east side of the river should experience more fluctuations in allele frequency due to genetic drift because it is smaller and there is little gene flow between the populations. Genetic drift has a greater impact on smaller populations, and the limited gene flow means that there is less opportunity for the eastern population to be "rescued" from the effects of genetic drift by new alleles flowing in from the west.

Question 18

Biologists recently discovered that black wolves got their coat color from exchanging genes with dogs.This is an example of
A) genetic drift.
B) gene pools.
C) gene flow.
D) a founder effect.
E) an adaptation.

Accepted Answer

Gene flow refers to the transfer of genes from one population to another. In this case, the genes for black coat color in dogs were transferred to the wolf population through interbreeding, resulting in the emergence of black wolves. This phenomenon is an example of gene flow.

Question 19

Suppose there are three isolated populations of a beetle: population A has had a constant population size of 10,000, population B has had a constant population size of 1,000, and population C has had a constant population size of 100.We would most expect to see an increase in the frequency of deleterious alleles in population _______ due to _______.
A) A; genetic drift
B) A; purifying selection
C) B; purifying selection
D) C; genetic drift
E) C; gene flow

Accepted Answer

Population C, which has had a constant population size of 100, is more likely to experience genetic drift, which can lead to an increase in the frequency of deleterious alleles. Population A, with a larger population size, is less likely to experience genetic drift, and both populations A and B are more likely to experience purifying selection, which would decrease the frequency of deleterious alleles. Population C is too small to experience much gene flow, so E is not a likely answer.

Question 20

A cricket has a diploid genome of 1.2 billion bp.Assume that there are about 200,000 individuals in the population and that the mutation rate is 1 per 100 million bp.About how many new mutations will occur in each generation of the population of crickets?
A) 1.2
B) 12
C) 200,000
D) 1 million
E) 2.4 million

Accepted Answer

Given a diploid genome size of 1.2 billion bp and a mutation rate of 1 per 100 million bp, each individual will have 12 new mutations per generation (1.2 billion / 100 million = 12). With 200,000 individuals, the total number of new mutations per generation is 12 mutations/individual * 200,000 individuals = 2.4 million mutations.

Quiz 20: Mechanisms of Evolution

Which vegetable was produced from wild mustard, Brassica oleracea, through continued selection for larger stems and flowers?

Which phrase best describes natural selection?

Suppose mutation and selection no longer occurred in a small, isolated population of nematodes.Which process would most likely continue operating, and what would be the most likely effect on the extent of genetic variation?

Yeast cells are sequenced periodically to examine them for new mutations.The table shows the results. What is the approximate mutation rate per generation for strain A?

Polydactyly (having more than five fingers on a hand) is much more common in some isolated human populations than it is elsewhere.This is most likely an example of a(n) _, which is due to the evolutionary mechanism called _.

The artificial selection experiments with bristle numbers in Drosophila illustrated which generality?

If variation at a given locus has no effect on the phenotypes of individuals, which evolutionary process will still occur at that locus?

Which two evolutionary processes would most likely act in opposite ways regarding their effects on the extent of genetic variation in a population?

Different populations of mice that were previously isolated now experience gene flow.What is the most likely outcome after several generations?

High-throughput sequencing reveals that ten new mutations have occurred in the coding regions of genes in an individual bat.If the coding regions of this bat comprise 100 million nucleotides per haploid genome, what is the mutation rate per nucleotide?

What is the main difference between Darwin and Wallace with respect to their contributions to evolutionary biology?

The haploid human genome contains about 3 billion bp.Given a mutation rate of 5 × 10^-⁹, how many new mutations would we expect on average in each diploid individual?

Which statement about Darwin is true?

Which understanding do modern biologists have that Darwin did not have?

Two populations of raccoons are similar in most respects, but the population on the east side of a river is much smaller than that on the west side.There is little gene flow between the populations.Which statement about these populations is most accurate?

Biologists recently discovered that black wolves got their coat color from exchanging genes with dogs.This is an example of

A cricket has a diploid genome of 1.2 billion bp.Assume that there are about 200,000 individuals in the population and that the mutation rate is 1 per 100 million bp.About how many new mutations will occur in each generation of the population of crickets?