Deck 21: Evidence and Mechanisms of Evolution

Question 1

Which of the following statements about the 1918-19 influenza pandemic is false?

A) Compared with most flu viruses, the virus of the pandemic hit young adults particularly hard.
B) There were more deaths from this virus than there were combat deaths in World War I.
C) The virus often triggered an especially intense reaction in the immune system.
D) The virus was the product of evolution.
E) All of the above are true; none is false.

Answer 1

E

Question 2

Which of the following best describes natural selection?

A) Chance variations in traits
B) The differential survival and reproduction of ­individuals
C) The processes that lead individuals to resemble their parents
D) The potential for all species to increase rapidly in number
E) The immutability of species

Answer 2

B

Question 3

Which of the following principles of Darwin's theory were guided by his reading of the economist Thomas Malthus?

A) The world is old.
B) Individuals resemble their parents.
C) There must be checks on survival and reproduction in nature, or else the world would become overcrowded.
D) Like compound interest, small successive changes in a trait each generation can lead to the large differences that we see between species.
E) Nature acts like the breeders of pigeon, selecting the traits most useful to the organism.

Answer 3

C

Question 4

The fitness of a genotype is a function of the

A) average rates of survival and reproduction of individuals with that genotype.
B) individuals that have the highest rates of both survival and reproduction.
C) individuals that have the highest rates of survival.
D) individuals that have the highest rates of reproduction.
E) average reproductive rate of individuals with that genotype.

Question 5

Disruptive selection maintains a bimodal distribution of bill size in the West African seedcracker because

A) bills of intermediate shapes are difficult to form.
B) the birds' two major food sources differ markedly in size and hardness.
C) males use their large bills in displays.
D) migrants introduce different bill sizes into the population each year.
E) older birds need larger bills than younger birds.

Question 6

Darwin published The Origin of Species

A) before 1840.
B) between 1841 and 1880.
C) between 1881 and 1920.
D) between 1921 and 1960.
E) after 1960.

Question 7

Why do most scientists and historians give Darwin more credit than Wallace regarding their contributions to evolutionary theory?

A) Only Darwin provided a mechanism for evolution.
B) Darwin provided more extensive evidence in support of evolution.
C) Darwin developed his ideas first.
D) Both a and b
E) Both b and c

Question 8

Although Darwin's voyage aboard the HMS Beagle took him around the world, most of his observations on natural history were made on the continent of _______ and its nearby islands.

A) Europe
B) North America
C) South America
D) Asia
E) Africa

Question 9

Which of the following is not a reason why trade-offs constrain evolution?

A) Most adaptations impose both fitness costs and benefits.
B) Structures such a horns and antlers are metabolically costly to produce, but result in more reproduction by the males that possess them.
C) Changes in allele frequencies may be influenced by chance events.
D) Ability to consume toxic prey may reduce mobility.
E) Adaptations can evolve only if the fitness benefits they confer exceed the costs they impose.

Question 10

Which of the following is the most likely reason that we need to develop a new flu vaccine every year?

A) The flu virus evolves due to negative selection.
B) The flu virus evolves due to positive selection.
C) The vaccine evolves due to negative selection.
D) Humans evolve from year to year.
E) Our immune system degrades over time.

Question 11

The appropriate unit for defining and measuring genetic variation is the

A) cell.
B) individual.
C) population.
D) community.
E) ecosystem.

Question 12

Which of the following statements about evolution is false?

A) Scientists can observe evolution in action.
B) Evolutionary theory can be applied to solve practical problems.
C) Biologists have accumulated a large body of evidence about the evolutionary changes that have occurred in the past.
D) Biologists have accumulated a large body of evidence about how evolutionary changes occur.
E) All of the above are true; none is false.

Question 13

Which of the following statements 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) All of the above

Question 14

Which of the following is not required for a population at Hardy-Weinberg equilibrium?

A) There is no migration between populations.
B) Natural selection is not acting on the alleles in the population.
C) Mating is random.
D) Multiple alleles must be present at every locus.
E) All of the above

Question 15

Laboratory selection experiments with fruit flies have demonstrated that

A) bristle number is not genetically controlled.
B) bristle number is not genetically controlled, but changes in bristle number are caused by the environment in which the fly is raised.
C) bristle number is genetically controlled, but there is little variation on which natural selection can act.
D) bristle number is genetically controlled, but selection cannot result in flies having more bristles than any individual in the original population had.
E) bristle number is genetically controlled, and selection can result in flies having more, or fewer, bristles than any individual in the original population had.

Question 16

Long-horned cattle have greater difficulty moving through heavily forested areas compared with cattle that have short or no horns, but long-horned cattle are better able to defend their young against predators. This contrast is an example of

A) an adaptation.
B) genetic drift.
C) natural selection.
D) a trade-off.
E) None of the above

Question 17

Which of the following is true?

A) Darwin and Wallace were both influenced by Malthus.
B) Wallace proposed a theory of evolution by natural selection that was similar to Darwin's.
C) Malthus claimed that because human population growth would outstrip any increases in food production, famine was a likely result.
D) Darwin realized that all populations had the capacity to rapidly increase in numbers.
E) All of the above

Question 18

The phenotype of an organism is

A) the type specimen of its species in a museum.
B) its genetic constitution, which governs its traits.
C) the chronological expression of its genes.
D) the physical expression of its genotype.
E) its adult form.

Question 19

According to the scientific definition of the word theory, a theory is

A) a hypothesis.
B) largely a matter of guesswork.
C) a large body of knowledge.
D) an estimate.
E) a supposition.

Question 20

Which statement about allele frequencies is not true?

A) The sum of all allele frequencies at a locus is always 1.
B) If there are two alleles at a locus and we know the frequency of one of them, we can obtain the frequency of the other by subtraction.
C) If an allele is missing from a population, its frequency in that population is 0.
D) If two populations have the same allele frequencies at a locus, they must have the same proportion of homozygotes at that locus.
E) If there is only one allele at a locus, its frequency is 1.

Question 21

In a hypothetical population of tree swallows, 18 individuals are homozygous for the c4 allele, 22 individuals are heterozygous for the allele, and 10 individuals lack the allele. What is the frequency of the c4 allele?

A) 0.29
B) 0.36
C) 0.40
D) 0.58
E) 0.80

Question 22

Which of the following statements is true?

A) Two different populations can have the same allele frequency but different genotype frequencies.
B) Populations that are polymorphic have only one allele at a locus.
C) If an allele is fixed in a population, that population is polymorphic.
D) All of the above
E) None of the above

Question 23

Three different alleles (b1, b2, and b3) at the b locus exist in a hypothetical population of juniper trees. If the frequency of b1 is 0.4, what can be said about the frequency of b3?

A) It cannot be less than 0.4.
B) It is 0.6.
C) It is 0.4.
D) It is 0.
E) Insufficient information is given to answer the question.

Question 24

Following a flood, migration from neighboring populations alters genotypic frequencies of a population of river-bottom midges. Assuming that the conditions for Hardy-Weinberg subsequently are met, how many generations of random mating are required to restore the genotypic frequencies to Hardy-Weinberg equilibrium?

A) 1
B) 2
C) Between 3 and 10
D) Between 11 and 20
E) More than 20

Question 25

In a population of field mice in the Sand Hills of Nebraska, some individuals have lighter coat colors than others. Which of the following would be the most straightforward way to observe whether the lighter coat color is a heritable trait?

A) Obtain DNA sequence from the individuals.
B) Breed the mice of both colors in the lab and observe the coat colors of their offspring.
C) Perform a chemical analysis of the coat hairs.
D) Conduct a field experiment to observe whether the lighter mice have a lower risk of predation than the darker mice.
E) Compare the number of offspring produced by light- and dark-colored mice.

Question 26

Given the diversity of dog breeds that exists, which of the following principles is likely to be true?

A) The original gene pool had little genetic variation.
B) Selection can yield considerable morphological change, outside the range of the original population.
C) The morphological traits seen must be at least somewhat heritable.
D) Both a and b
E) Both b and c

Question 27

Which of the following statements about the Hardy-Weinberg equilibrium is true?

A) It explains why dominant alleles do not necessarily replace recessive alleles in a population.
B) It applies only to populations in which there is gene flow.
C) It assumes that populations are small.
D) It assumes that individuals prefer to mate with individuals with certain genotypes.
E) None of the above

Question 28

Which of the following is an adaptation?

A) The lion's speed, which enables the animal to capture its prey
B) The process by which a lion's speed increases over many generations
C) Differential survival
D) Both a and b
E) Both b and c

Question 29

What is the most likely vegetable to be produced from wild mustard, Brassica oleracea, given continued selection for larger stems and flowers?

A) Kale
B) Brussels sprouts
C) Broccoli
D) Cabbage
E) Cauliflower

Question 30

In a hypothetical population of sawflies, 20 percent of the population is homozygous for allele A and 45 percent is homozygous for allele a. Assuming that A and a are the only alleles at this locus, what percent of the population is heterozygous?

A) 10 percent
B) 20 percent
C) 35 percent
D) 45 percent
E) Insufficient information is given to answer the question.

Question 31

Which of the following statements about allele frequencies is true?

A) It is possible to have a negative allele frequency.
B) Allele frequencies can be greater than 1 in some populations.
C) The sum of all allele frequencies is 0.
D) All of the above
E) None of the above

Question 32

Which of the following statements about the relationship between genotype and phenotype is true?

A) A given genotype always produces a specific phenotype.
B) Genotypes alone determine all phenotypes.
C) A particular phenotype can be produced by more than one genotype.
D) Dominance makes the study of the genetic basis of natural selection easy.
E) None of the above

Question 33

Which of the following is not a goal of population genetics?

A) Explaining the patterns of genetic variation
B) Explaining how genotypic information is expressed as phenotypic traits
C) Explaining the origins of genotypic variation
D) Understanding the mechanisms by which allele frequencies change in populations
E) Explaining how genetic variation is maintained

Question 34

If a population with two alleles is at Hardy-Weinberg equilibrium and the frequency of one allele is 0.7, what is the heterozygote frequency?

A) 0.7
B) 0.42
C) 0.3
D) 0.21
E) Insufficient information is given to answer the question.

Question 35

Assuming that there are only two alleles at a given locus, if the frequency of one allele is 0.6, what is the frequency of the other allele?

A) -0.6
B) 0
C) 0.4
D) 0.6
E) 1

Question 36

The artificial selection experiments with bristle number in Drosophila illustrate which of the following generalities?

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) A particular phenotype can be produced by more than one genotype.
D) Such experiments usually take thousands of generations to achieve their results.
E) Bristle number is a genotype, not a phenotype.

Question 37

Which of the following is not a condition for the Hardy-Weinberg equilibrium?

A) Absence of gene flow
B) Absence of differential survival among genotypes
C) Random mating of individuals with respect to genotype
D) Absence of genetic drift that would cause chance fluctuations of allele frequencies
E) Small population size

Question 38

In order for a population to evolve,

A) its members must have heritable genetic variation.
B) natural selection must be acting on the population.
C) all members of the population must have identical phenotypes.
D) Both a and b
E) None of the above

Question 39

Use the following to answer questions:
In a population of 200 individuals, 72 are homozygous recessive for the character of eye color (cc). One hundred individuals from this population die from a fatal disease. Thirty-six of the survivors are homozygous recessive.
In the original population, the frequency of the dominant allele is

A) 0.16.
B) 0.36.
C) 0.40.
D) 0.48.
E) 0.60.

Question 40

Which of the following statements is false?

A) Darwin's theory of evolution by natural selection was influenced by his experiences as a pigeon breeder.
B) Individuals evolve according to Darwin's theory.
C) Death rates in nature are usually high.
D) Offspring tend to resemble their parents.
E) All of the above are true; none is false.

Question 41

Natural selection works _______ on the genotype and _______ on the phenotype.

A) directly; directly
B) directly; indirectly
C) directly; not at all
D) indirectly; directly
E) indirectly; not at all

Question 42

In pin flowers, the style is _______ and the stamens are _______.

A) long; long
B) long; short
C) short; long
D) short; short
E) short; absent

Question 43

Use the following to answer questions:
Suppose you have a population of flour beetles with 1,000 individuals. Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by b/b. Red is dominant to black, so B/B and B/b genotypes are red. Assume the population is in Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.
What would be the expected frequencies of the red and black phenotypes?

A) 0.5 red; 0.5 black
B) 0.75 red; 0.25 black
C) 0.25 red; 0.75 black
D) 0
E) Insufficient information is given to answer the question.

Question 44

Which of the following statements about mutations is false?

A) Mutation rates are very low for most loci.
B) Mutations are random with respect to the adaptive needs of organisms.
C) Most mutations are either harmful or neutral.
D) Only rarely does a human carry a new mutation in his or her genome.
E) The current human population carries billions of new mutations that were not present in previous generations.

Question 45

Which of the following statements about population bottlenecks is false?

A) They are an extreme example of genetic drift.
B) They can result in changes in allele frequencies.
C) They can result in the loss of genetic variation.
D) They arise from severe reductions in population size.
E) All of the above are true; none is false.

Question 46

Use the following to answer questions:
Suppose you have a population of flour beetles with 1,000 individuals. Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by b/b. Red is dominant to black, so B/B and B/b genotypes are red. Assume the population is in Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.
What would be the expected red and black allele frequencies if 1000 black individuals migrated into the population?

A) 0.75 red; 0.25 black
B) 0.25 red; 0.75 black
C) 0.33 red; 0.67 black
D) They would not change because the population would still be in Hardy-Weinberg equilibrium.
E) None of the above

Question 47

When researchers observe populations that have large deviations from Hardy-Weinberg equilibrium, they can safely dismiss which of the following mechanisms as the explanation for the deviation?

A) Natural selection
B) Gene flow
C) Nonrandom mating
D) Mutation
E) None of the above

Question 48

Which of the following processes results in adaptation?

A) Mutation
B) Natural selection
C) Genetic drift
D) Migration
E) Nonrandom mating

Question 49

Which of the following is most likely responsible for the low number of inversion types seen in North American populations of Drosophila suboscura?

A) Mutation
B) Nonrandom mating
C) Genetic drift
D) Heterozygous advantage
E) Sexual selection

Question 50

The pin/thrum flower polymorphism in primroses

A) is an example of nonrandom mating.
B) ensures that pollination occurs between individuals of the same genotype.
C) alters allele frequencies.
D) exists because pollen grains from pin and thrum flowers are deposited on the same parts of the body of insects that visit the flowers.
E) is a form of self-fertilization.

Question 51

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 of the following would you not expect to see in whooping cranes?

A) Very low levels of genetic variation
B) Very few heterozygous individuals
C) Differences in allele frequency between current populations of cranes and historical populations
D) Considerable genetic polymorphism
E) All of the above would be seen in whooping cranes.

Question 52

Which of the following statements about fitness and natural selection is true?

A) The fitness of individuals of a particular phenotype is a function of the probability that such individuals survive, divided by the average number of offspring they produce.
B) The fitness of individuals of a particular phenotype is a function of the probability that such individuals survive, multiplied by the average number of offspring they produce.
C) Changes in the absolute numbers of offspring necessarily lead to changes in allele frequencies from one generation to the next.
D) Both a and b
E) Both b and c

Question 53

The ultimate origin of genetic variation is

A) genetic drift.
B) mutation.
C) natural selection.
D) a founder effect.
E) nonrandom mating.

Question 54

Use the following to answer questions:
Suppose you have a population of flour beetles with 1,000 individuals. Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by b/b. Red is dominant to black, so B/B and B/b genotypes are red. Assume the population is in Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.
What would be the allele frequencies (red, followed by black) if a population bottleneck occurred and only four individuals survived: one female red heterozygote and three black males?

A) 0.875; 0.125
B) 0.125; 0.875
C) 0.25; 0.75
D) 0.75; 0.25
E) 0.5; 0.5

Question 55

Which of the following statements about self-fertilization is false?

A) It is a form of nonrandom mating.
B) It can cause deviations from the Hardy-Weinberg equilibrium.
C) It reduces the frequency of heterozygotes.
D) It increases the frequency of homozygotes.
E) It changes allele frequencies.

Question 56

Use the following to answer questions:
In a population of 200 individuals, 72 are homozygous recessive for the character of eye color (cc). One hundred individuals from this population die from a fatal disease. Thirty-six of the survivors are homozygous recessive.
In the new population, the frequency of the dominant allele is

A) 0.16.
B) 0.36.
C) 0.40.
D) 0.48.
E) 0.60.

Question 57

Use the following to answer questions:
Suppose you have a population of flour beetles with 1,000 individuals. Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by b/b. Red is dominant to black, so B/B and B/b genotypes are red. Assume the population is in Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.
If the population in the previous question mated randomly and no other evolutionary forces operated, what would be the allele frequencies of their offspring?

A) 0.875; 0.125
B) 0.125; 0.875
C) 0.25; 0.75
D) 0.75; 0.25
E) 0.5; 0.5

Question 58

Which of the following statements about genetic drift as an evolutionary factor is true?

A) It is more significant in a population with small numbers than in a population with large numbers.
B) It is responsible for the selection of mutations.
C) It is connected to the movements of alleles between populations of a single species.
D) Its strength is proportional to the size of a population: the larger the population, the greater the force.
E) Both a and b

Question 59

Use the following to answer questions:
In a population of 200 individuals, 72 are homozygous recessive for the character of eye color (cc). One hundred individuals from this population die from a fatal disease. Thirty-six of the survivors are homozygous recessive.
How many heterozygous individuals are expected in the new population?

A) 16
B) 36
C) 40
D) 48
E) 60

Question 60

Use the following to answer questions:
Suppose you have a population of flour beetles with 1,000 individuals. Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by b/b. Red is dominant to black, so B/B and B/b genotypes are red. Assume the population is in Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.
What would be the expected frequencies of the homozygous dominant, heterozygous, and homozygous recessive after 100 generations?

A) 0.75; 0.20; 0.05
B) 0.25; 0.5; 0.25
C) All red, because it is the natural color.
D) All black, because all red alleles would mutate to black.
E) None of the above

Question 61

Which of the following is a plausible explanation for the typically slow rates of evolution over the long term?

A) Most populations have little genetic variation.
B) Natural selection is typically a stabilizing phenomenon.
C) Directional selection is commonplace.
D) Genetic drift counters the effects of selection, particularly in large populations.
E) Mutation rates are very high.

Question 62

Which of the following is least likely to help maintain genetic variation?

A) Directional selection
B) The mating advantage of heterozygotes
C) Varying environments
D) Sexual recombination
E) Frequency-dependent selection

Question 63

Which of the following statements about sexual selection is true?

A) Traits favored by sexual selection are often costly to males.
B) Sexual selection operates primarily on survival success.
C) Females gain a fitness benefit by choosing males on the basis of traits that can easily be faked.
D) Darwin's contemporaries immediately recognized the importance of his ideas about sexual selection.
E) Sexual selection applies to the ability of individuals of one sex to compete for access to members of the opposite sex, not to matters of sexual attractiveness.

Question 64

Which of the following explanations has not been proposed as an explanation for the existence of sexual reproduction?

A) Sexual reproduction facilitates repair of damaged DNA.
B) Sexual reproduction promotes the elimination of deleterious mutations.
C) Sexual reproduction accelerates Muller's ratchet.
D) Sexual reproduction creates a great diversity of genetic combinations that allows populations to adapt to the presence of pathogens.
E) None of the above; all of the above explanations have been proposed for the existence of sexual reproduction.

Question 65

What was Darwin's explanation for the evolution of bright colors and other apparently useless (and potentially deleterious) but conspicuous characters in males of many species?

A) Stabilizing selection
B) Genetic drift
C) Sexual selection
D) Disruptive selection
E) Gene flow

Question 66

In Tim Birkhead's study of zebra finches, male birds fed water with added carotenoids

A) had much brighter bills than control males had.
B) were preferred by females.
C) developed thicker skins than control males did.
D) had stronger immune systems than control males had.
E) All of the above

Question 67

Which of the following tends to reduce genetic variation within populations?

A) Genetic drift
B) Stabilizing selection
C) Directional selection
D) All of the above
E) None of the above

Question 68

Which of the following is a benefit of sexual reproduction?

A) It generates new combinations of alleles upon which selection can act.
B) It breaks up adaptive combinations of genes.
C) The division of offspring into separate genders reduces the overall reproductive rate.
D) It promotes Muller's ratchet.
E) None of the above

Question 69

Which of the following modes of selection results in a decrease in variation?

A) Stabilizing selection only
B) Directional selection only
C) Disruptive selection only
D) Both directional and disruptive selection
E) Both stabilizing and directional selection

Question 70

Which of the following modes of selection leads to a reduction in variation but no change in the mean?

A) Stabilizing selection
B) Directional selection
C) Disruptive selection
D) Both a and c
E) Both b and c

Question 71

Which of the following conditions would be most conducive for the evolution of sexual reproduction and recombination?

A) Large population size
B) Steady temperatures
C) A very efficient DNA repair system
D) The elimination of pathogens
E) A rapidly changing environment

Question 72

Which of the following modes of selection arises when individuals at both extremes of the distribution have high fitness?

A) Stabilizing selection
B) Directional selection
C) Disruptive selection
D) Both a and b
E) Both b and c

Question 73

Tim Birkhead and his colleagues were able to boost the immune systems of male zebra finches and increase their attractiveness to females by

A) enlarging their tails.
B) injecting them with hormones.
C) feeding them carotenoid pigments.
D) increasing their caloric intake.
E) injecting them with phytohemagglutinin.

Question 74

Suppose that females of a species of beetles prefer to mate with males that have relatively rare color patterns. This observation would be an illustration of

A) Muller's ratchet.
B) genetic drift.
C) the founder effect.
D) frequency-dependent selection.
E) disruptive selection.

Question 75

Muller's ratchet is the

A) breaking down of adaptive combinations of genes by recombination.
B) elimination of deleterious mutations due to sexual reproduction.
C) accumulation of deleterious mutations in asexual lineages.
D) crossing over and independent assortment of chromosomes during meiosis.
E) maintenance of genetic variation via disruptive selection.

Question 76

Malte Andersson's study of widowbirds demonstrated that

A) females prefer males with unaltered tails.
B) the preferences of females change according to the season.
C) sexually selected traits have no benefits or costs to survivorship.
D) long tails help males compete against other males.
E) females prefer males with longer-than-average tails.

Question 77

The sizes of horns in males of a particular beetle have an interesting distribution: the highest frequencies are around 15 millimeters and 30 millimeters, with few individuals in between. Based on this observation, which of the following modes of selection is most likely to be operating on these horns?

A) Stabilizing selection
B) Directional selection
C) Concentrated selection
D) Disruptive selection
E) Purifying selection

Question 78

Studies of enzyme genotypes and flight in Colias butterflies showed that

A) males that are heterozygous at PGI are always inferior in flight compared to homozygotes.
B) males that are heterozygous at PGI have greater mating success than homozygous males because they are able to fly farther in a broad range of temperatures.
C) genotypes at PGI do not affect flight ability.
D) flight ability and mating success are not correlated.
E) flight ability can be explained by Muller's ratchet.

Question 79

The exchange of allele b1 for b2 at the b locus does not affect the fitness of individuals. These alleles can thus be considered _______ alleles.

A) selected
B) neutral
C) neutered
D) Muller's
E) deleterious

Question 80

Subpopulations often vary genetically from one another because they

A) are subject to stabilizing selection.
B) are subject to different selective pressures.
C) experience a high rate of gene flow.
D) experience different rates of mutation.
E) All of the above