23.4 Natural selection is the only mechanism that consistently causes adaptive evolution

Question 1

15) In a hypothetical populationʹs gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations?
A) The proportions of both types of homozygote should decrease.
B) The proportion of the population that is heterozygous at this locus should remain
constant.
C) The populationʹs average heterozygosity should increase.
D) Both (A)and (B)
E) Both (A)and (C)

Answer 1

E) Both (A)and (C)

Question 2

47) Natural selection is most nearly the same as A) diploidy.
B) gene flow.
C) genetic drift.
D) non-random mating.
E) differential reproductive success.

Answer 2

E) differential reproductive success.

Question 3

The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA.
48) The outcome of the conflict between bacteria and bacteriophage at any point in time results from
A) frequency-dependent selection.
B) evolutionary imbalance.
C) heterozygote advantage.
D) neutral variation.
E) genetic variation being preserved by diploidy.

Answer 3

A) frequency-dependent selection.

Question 4

The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA.

49) Over the course of evolutionary time, what should occur?
A) Methylated DNA should become fixed in the gene pools of bacterial species.
B) Nonmethylated DNA should become fixed in the gene pools of bacteriophages.
C) Methylated DNA should become fixed in the gene pools of bacteriophages.
D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.
E) Both A and B are correct.

Answer 4

D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.

Question 5

50) Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive):
1. Natural selection
2. Microevolution
3. Intrasexual selection 4. Evolution
5. Sexual selection
A) 4, 1, 2, 3, 5
B) 4, 2, 1, 3, 5
C) 4,2,1,5,3
D) 1, 4, 2, 5, 3
E) 1, 2, 4, 5, 3

Answer 5

C) 4,2,1,5,3

Question 6

51) Sexual dimorphism is most often a result of
A) pansexual selection.
B) stabilizing selection.
C) intrasexual selection.
D) intersexual selection.
E) artificial selection.

Answer 6

D) intersexual selection.

Question 7

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birdsʹ diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the maleʹs feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal).

52) During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation?
A) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations.
B) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations.
C) There should be directional selection for bright red feathers in males.
D) All three of these.
E) Only B and C.

Answer 7

D) All three of these.

Question 8

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birdsʹ diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the maleʹs feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal).

53) Which of the following terms are appropriately applied to the situation described in the previous question?
A) Sexual selection
B) Mate choice
C) Intersexual selection
D) All three of these
E) Only B and C

Answer 8

D) All three of these

Question 9

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birdsʹ diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the maleʹs feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal).

54) The situation as described in the paragraph above should select most directly against males that
A) are unable to distinguish food items that are red from those of other colors.
B) are older, but still healthy.
C) are capable of defending only moderately sized territories.
D) have slightly lower levels of testosterone during breeding season than have other
males.
E) have no prior experience courting female house finches

Answer 9

A) are unable to distinguish food items that are red from those of other colors.

Question 10

Adult male humans generally have deeper voices than do adult female humans, as the direct result of higher levels of testosterone causing growth of the larynx.

55) If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females, and increasing larynx size in adult males, then
A) sexual dimorphism was developing over time in these species.
B) intrasexual selection seems to have occurred.
C) the ʺgood genesʺ hypothesis was refuted by these data.
D) stabilizing selection was occurring in these species concerning larynx size.
E) selection was acting more directly upon genotype than upon phenotype.

Answer 10

A) sexual dimorphism was developing over time in these species.

Question 11

Adult male humans generally have deeper voices than do adult female humans, as the direct result of higher levels of testosterone causing growth of the larynx.

56) Which addition to the information in the paragraph above would make more than one of the answers listed in the previous question correct?
A) If larynx size was also affected by the amount the larynx was used (i.e., the amount of vocalization).
B) If males prefer to mate with females possessing higher voices.
C) If females killed female offspring whose voices were too deep.
D) If the trend described above was seen in the fossil record of only one species of ape.

Answer 11

C) If females killed female offspring whose voices were too deep.

Question 12

Adult male humans generally have deeper voices than do adult female humans, as the direct result of higher levels of testosterone causing growth of the larynx.

57) If one excludes the involvement of gender in the situation described in the paragraph above, then the pattern that is apparent in the fossil record is most similar to one that should be expected from
A) pansexual selection.
B) directional selection.
C) disruptive selection.
D) stabilizing selection.
E) asexual selection.

Answer 12

C) disruptive selection.

Question 13

58) The Darwinian fitness of an individual is measured most directly by
A) the number of its offspring that survive to reproduce.
B) the number of ʺgood genesʺ it possesses.
C) the number of mates it attracts.
D) its physical strength.
E) how long it lives.

Answer 13

A) the number of its offspring that survive to reproduce.

Question 14

59) When we say that an individual organism has a greater fitness than another individual, we specifically mean that the organism
A) lives longer than others of its species.
B) competes for resources more successfully than others of its species.
C) mates more frequently than others of its species.
D) utilizes resources more efficiently than other species occupying similar niches.
E) leaves more viable offspring than others of its species.

Answer 14

E) leaves more viable offspring than others of its species.

Question 15

60) Which of the following statements best summarizes evolution as it is viewed today? A) It is goal-directed.
B) It represents the result of selection for acquired characteristics.
C) It is synonymous with the process of gene flow.
D) It is the descent of humans from the present-day great apes.
E) It is the differential survival and reproduction of the most-fit phenotypes.

Answer 15

E) It is the differential survival and reproduction of the most-fit phenotypes.

Question 16

61) If neutral variation is truly ʺneutral,ʺ then it should have no effect on
A) nucleotide diversity.
B) average heterozygosity.
C) our ability to measure the rate of evolution.
D) relative fitness.
E) gene diversity.

Answer 16

D) relative fitness.

Question 17

62) Which describes an African butterfly species that exists in two strikingly different color patterns?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Answer 17

D) disruptive selection

Question 18

63) Which describes brightly colored peacocks mating more frequently than drab peacocks? A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Answer 18

E) sexual selection

Question 19

64) Most Swiss starlings produce four to five eggs in each clutch. Those producing fewer or more than this have reduced fitness. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Answer 19

C) stabilizing selection

Question 20

65) Fossil evidence indicates that horses have gradually increased in size over geologic time. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Answer 20

B) directional selection

Question 21

66) The average birth weight for human babies is about 3 kg. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Answer 21

C) stabilizing selection

Question 22

67) A certain species of land snail exists as either a cream color or a solid brown color. Intermediate individuals are relatively rare. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual
selection

Answer 22

D) disruptive selection

Question 23

68) Cattle breeders have improved the quality of meat over the years by which process? A) artificial selection
B) directional selection
C) stabilizing selection
D) A and B
E) A and C

Answer 23

D) A and B

Question 24

69) The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infantʹs diet lacks the amino acid, phenylalanine. What maintains the presence of this harmful allele in a populationʹs gene pool?
A) heterozygote advantage B) stabilizing selection
C) diploidy
D) balancing selection

Answer 24

C) diploidy

Question 25

70) Mules are relatively long-lived and hardy organisms that cannot, generally speaking, perform successful meiosis. Consequently, which statement about mules is true?
A) They have a relative evolutionary fitness of zero.
B) Their offspring have less genetic variation than the parents.
C) Mutations cannot occur in their genomes.
D) If crossing-over happens in mules, then it must be limited to prophase of mitosis.
E) When two mules interbreed, genetic recombination cannot occur by meiotic crossing over, but only by the act of fertilization.

Answer 25

A) They have a relative evolutionary fitness of zero.

Question 26

71) Heterozygote advantage should be most closely linked to which of the following?
A) sexual selection
B) stabilizing selection
C) random selection
D) directional selection
E) disruptive selection

Answer 26

B) stabilizing selection

Question 27

72) In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?
A) disruptive selection
B) directional selection
C) stabilizing selection
D) sexual selection
E) No selection would operate because the population is in Hardy-Weinberg
equilibrium.

Answer 27

B) directional selection

Question 28

75) Male satin bowerbirds adorn structures that they build, called ʺbowers,ʺ with parrot feathers, flowers, and other bizarre ornaments in order to attract females. Females inspect the bowers and, if suitably impressed, allow males to mate with them. The evolution of this male behavior is due to
A) frequency-dependent selection.
B) artificial selection.
C) sexual selection.
D) natural selection.
E) disruptive selection.

Answer 28

C) sexual selection.

Question 28

74) If the curve shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations, then which of these is (are) probably occurring?
1. immigration or emigration 2. directional selection
3. adaptation
4. genetic drift
5. disruptive selection
A) 1 only
B) 4 only
C) 2and3
D) 4 and 5
E) 1, 2, and 3

Answer 28

C) 2and3

Question 29

77) The same gene that causes various coat patterns in wild and domesticated cats also causes the cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations?
A) Evolution is progressive and tends toward a more perfect population.
B) Phenotype is often the result of compromise.
C) Natural selection reduces the frequency of maladaptive genes in populations over the course of time.
D) Polygenic inheritance is generally maladaptive, and should become less common in future generations.
E) In all environments, coat pattern is a more important survival factor than is eye-muscle tone.

Answer 29

B) Phenotype is often the result of compromise.

Question 29

76) When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of
A) sexual selection.
B) disruptive selection.
C) balancing selection.
D) stabilizing selection.
E) frequency-dependent selection.

Answer 29

E) frequency-dependent selection.

Question 30

78) A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these mammals do not seem to be optimally arranged is because
A) natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time.
B) natural selection operates in ways that are beyond the capability of the human mind to comprehend.
C) in many cases, phenotype is not merely determined by genotype, but by the environment as well.
D) though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design.
E) natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

Answer 30

E) natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

Question 31

79) There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception?
A) Advantageous alleles do not arise on demand.
B) A populationʹs evolution is limited by historical constraints.
C) Adaptations are often compromises.
D) Evolution can be influenced by environmental change.

Answer 31

A) Advantageous alleles do not arise on demand.

Question 32

2) There are 40 individuals in population 1, all of which have genotype A1A1, and there are 25 individuals in population 2, all of genotype A2A2. Assume that these populations are located far from one another and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is mostly likely an example of
A) genetic drift.
B) gene flow.
C) disruptive selection.
D) discrete variation.
E) directional selection.

Answer 32

A) genetic drift.

Question 33

3) Natural selection changes allele frequencies in populations because some __________ survive and reproduce more successfully than others.
A) alleles
B) loci
C) gene pools
D) species
E) individuals

Answer 33

E) individuals

Question 34

4) No two people are genetically identical, except for identical twins. The chief cause of genetic variation among human individuals is
A) new mutations that occurred in the preceding generation.
B) the reshuffling of alleles in sexual reproduction.
C) genetic drift due to the small size of the population.
D) geographic variation within the population.
E) environmental effects.

Answer 34

B) the reshuffling of alleles in sexual reproduction.

Question 35

5) Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating
A) the bottleneck effect.
B) stabilizing selection.
C) frequency-dependent selection.
D) neutral variation.
E) disruptive selection.

Answer 35

B) stabilizing selection.