AP Biology Chapter 23

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1

Which of these is a statement that Darwin would have rejected?
A) Environmental change plays a role in evolution.
B) The smallest entity that can evolve is an individual organism.
C) Individuals can acquire new characteristics as they respond to new environments or
situations.
D) Inherited variation in a population is a necessary precondition for natural selection to
operate.
E) Natural populations tend to produce more offspring than the environment can
support.

B

2

Which definition of evolution would have been most foreign to Charles Darwin during his
lifetime?
A) change in gene frequency in gene pools
B) descent with modification
C) the gradual change of a populationʹs heritable traits over generations
D) populations becoming better adapted to their environments over the course of
generations
E) the appearance of new varieties and new species with the passage of time

A

3

About which of these did Darwin have a poor understanding?
A) that individuals in a population exhibit a good deal of variation
B) that much of the variation between individuals in a population is inherited
C) the factors that cause individuals in populations to struggle for survival
D) the sources of genetic variations among individuals
E) how a beneficial trait becomes more common in a population over the course of
generations

D

4

If, on average, 46% of the loci in a speciesʹ gene pool are heterozygous, then the average
homozygosity of the species should be
A) 23%
B) 46%
C) 54%
D) 92%
E) There is not enough information to say

C

5

Which of these variables is likely to undergo the largest change in value as the result of a
mutation that introduces a brand-new allele into a populationʹs gene pool at a locus that
had formerly been fixed?
A) Average heterozygosity
B) Nucleotide variability
C) Geographic variability
D) Average number of loci

A

6

Which of these is the smallest unit upon which natural selection directly acts?
A) a speciesʹ gene frequency
B) a populationʹs gene frequency
C) an individualʹs genome
D) an individualʹs genotype
E) an individualʹs phenotype

E

7

) Which of these is the smallest unit that natural selection can change?
A) a speciesʹ gene frequency
B) a populationʹs gene frequency
C) an individualʹs genome
D) an individualʹs genotype
E) an individualʹs phenotype

B

8

Which of these evolutionary agents is most consistent at causing populations to become
better suited to their environments over the course of generations?
A) Mutation
B) Non-random mating
C) Gene flow
D) Natural selection
E) Genetic drift

D

9

Which statement about the beak size of finches on the island of Daphne Major during
prolonged drought is true?
A) Each bird evolved a deeper, stronger beak as the drought persisted.
B) Each bird developed a deeper, stronger beak as the drought persisted.
C) Each birdʹs survival was strongly influenced by the depth and strength of its beak as
the drought persisted.
D) Each bird that survived the drought produced only offspring with deeper, stronger
beaks than seen in the previous generation.
E) The frequency of the strong-beak alleles increased in each bird as the drought
persisted.

C

10

Each of the following has a better chance of influencing gene frequencies in small
populations than in large populations, but which one most consistently requires a small
population as a precondition for its occurrence?
A) Mutation
B) Non-random mating
C) Genetic drift
D) Natural selection
E) Gene flow

C

11

In modern terminology, diversity is understood to be a result of genetic variation. Sources
of variation for evolution include all of the following except
A) mistakes in translation of structural genes.
B) mistakes in DNA replication.
C) translocations and mistakes in meiosis.
D) recombination at fertilization.
E) recombination by crossing over in meiosis.

A

12

A trend toward the decrease in the size of plants on the slopes of mountains as altitudes
increase is an example of
A) a cline.
B) a bottleneck.
C) relative fitness.
D) genetic drift.
E) geographic variation.

A

13

The higher the proportion of loci that are ʺfixedʺ in a population, the lower is that
populationʹs
A) nucleotide variability.
B) genetic polyploidy.
C) average heterozygosity.
D) A, B, and C
E) A and C only

E

14

) Which statement about variation is true?
A) All phenotypic variation is the result of genotypic variation.
B) All genetic variation produces phenotypic variation.
C) All nucleotide variability results in neutral variation.
D) All new alleles are the result of nucleotide variability.
E) All geographic variation results from the existence of clines.

D

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)

E

16

) Rank the following 1-base point mutations (from most likely to least likely) with respect to
their likelihood of affecting the structure of the corresponding polypeptide:
1. insertion mutation deep within an intron
2. substitution mutation at the 3rd position of an exonic codon
3. substitution mutation at the 2nd position of an exonic codon
4. deletion mutation within the first exon of the gene
A) 1, 2, 3, 4
B) 4, 3, 2, 1
C) 2, 1, 4, 3
D) 3, 1, 4, 2
E) 2, 3, 1, 4

B

17

Sponges are known to contain a single Hox gene. Most invertebrates have a cluster of 10
similar Hox genes, all located on the same chromosome. Most vertebrates have four such
clusters of Hox genes, located on four non-homologous chromosomes. The process
responsible for the change in number of Hox genes from sponges to invertebrates was most
likely __________, whereas a different process that could have potentially contributed to the
clusterʹs presence on more than one chromosome was __________.
I. binary fission
II. translation
III. gene duplication
IV. non-disjunction
V. transcription
A) I, II
B) II, III
C) II, V
D) III, IV
E) III, V

D

18
card image

Which of these represents the treatment option that is most likely to avoid the production
of drug-resistant HIV (assuming no drug interactions or side effects)?
A) using a series of NAs, one at a time, and changed about once a week
B) using a single PI, but slowly increasing the dosage over the course of a week
C) using high doses of NA and a PI at the same time for a period not to exceed 1 day
D) using moderate doses of NA and of two different PIʹs at the same time for several
months

D

19
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) Within the body of an HIV-infected individual who is being treated with a single NA, and
whose HIV particles are currently vulnerable to this NA, which of these situations can
increase the virusʹ relative fitness?
1. mutations resulting in RTs with decreased rates of nucleotide mismatch
2. mutations resulting in RTs with increased rates of nucleotide mismatch
3. mutations resulting in RTs that have proofreading capability
A) 1 only
B) 2 only
C) 3 only
D) 1 and 3
E) 2 and 3

B

20
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HIV has 9 genes in its RNA genome. Every HIV particle contains two RNA molecules, each
molecule containing all 9 genes. If, for some reason, the two RNA molecules within a single
HIV particle do not have identical sequences, then which of these terms can be applied due
to the existence of the non-identical regions?
A) homozygous
B) gene variability
C) nucleotide variability
D) average heterozygosity
E) all except A

E

21
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) If two genes from one RNA molecule become detached and then, as a unit, get attached to
one end of the other RNA molecule within a single HIV particle, which of these is true?
A) There are now fewer genes within the viral particle.
B) There are now more genes within the viral particle.
C) A point substitution mutation has occurred in the retroviral genome.
D) The retroviral equivalent of crossing-over has occurred, no doubt resulting in a
heightened positive effect.
E) One of the RNA molecules has experienced gene duplication as the result of
translocation.

E

22

The DNA polymerases of all cellular organisms have proofreading capability. This
capability tends to reduce the introduction of
A) extra genes by gene duplication events.
B) chromosomal translocation.
C) genetic variation by mutations.
D) proofreading capability into prokaryotes

C

23

Which of these makes determining the evolutionary relatedness of different species based
on the amino acid sequence of homologous proteins generally less accurate than
determinations of relatedness based on the nucleotide sequences of homologous genes?
A) Silent mutations
B) Gene duplications
C) Translocation events that change gene sequences
D) Crossing-over
E) Independent assortment

A

24

) Which is a true statement concerning genetic variation?
A) It is created by the direct action of natural selection.
B) It arises in response to changes in the environment.
C) It must be present in a population before natural selection can act upon the
population.
D) It tends to be reduced by the processes involved when diploid organisms produce
gametes.
E) A population that has a higher average heterozygosity has less genetic variation than
one with a larger average heterozygosity.

C

25
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B

26
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What is the most reasonable conclusion that can be drawn from the fact that the frequency
of the recessive trait (aa) has not changed over time?
A) The population is undergoing genetic drift.
B) The two phenotypes are about equally adaptive under laboratory conditions.
C) The genotype AA is lethal.
D) There has been a high rate of mutation of allele A to allele a.
E) There has been sexual selection favoring allele a.

B

27
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What is the estimated frequency of allele A in the gene pool?
A) 0.05
B) 0.25
C) 0.50
D) 0.75
E) 1.00

C

28
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What proportion of the population is probably heterozygous (Aa) for this trait?
A) 0.05
B) 0.25
C) 0.50
D) 0.75
E) 1.00

C

29
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In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the
frequency of the allele a is 0.4. What is the percentage of the population that is homozygous
for this allele?
A) 4
B) 16
C) 32
D) 36
E) 40

B

30
card image

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the
frequency of allele a is 0.1. What is the percentage of the population that is heterozygous for
this allele?
A) 90
B) 81
C) 49
D) 18
E) 10

D

31
card image

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the
frequency of allele a is 0.2. What is the frequency of individuals with Aa genotype?
A) 0.20
B) 0.32
C) 0.42
D) 0.80
E) Genotype frequency cannot be determined from the information provided.

B

32
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You sample a population of butterflies and find that 42% are heterozygous at a particular
locus. What should be the frequency of the recessive allele in this population?
A) 0.09
B) 0.30
C) 0.49
D) 0.70
E) Allele frequency cannot be determined from this information.

E

33

In a hypothetical population of 1,000 people, tests of blood-type genes show that 160 have the genotype AA, 480 have the genotype AB, and 360 have the genotype BB.

What is the frequency of the B allele?
A) 0.001
B) 0.002
C) 0.100
D) 0.400
E) 0.600

E

34

In a hypothetical population of 1,000 people, tests of blood-type genes show that 160 have the genotype
AA, 480 have the genotype AB, and 360 have the genotype BB.

If there are 4,000 children born to this generation, how many would be expected to have AB
blood under the conditions of Hardy-Weinberg equilibrium?
A) 100
B) 960
C) 1,920
D) 2,000
E) 2,400

C

35

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea
patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming
Hardy-Weinberg equilibrium, what is the value of q for this population?
A) 0.36
B) 0.60
C) 0.64
D) 0.75
E) 0.80

E

36

In the year 2500, five male space colonists and five female space colonists (all unrelated to each other)
settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring
randomly mate for generations. All ten of the original colonists had free earlobes, and two were
heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.

Which of these is closest to the allele frequency in the founding population?
A) 0.1 a, 0.9 A
B) 0.2 a, 0.8 A
C) 0.5 a, 0.5 A
D) 0.8 a, 0.2 A
E) 0.4 a, 0.6 A

A

37

In the year 2500, five male space colonists and five female space colonists (all unrelated to each other)
settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring
randomly mate for generations. All ten of the original colonists had free earlobes, and two were
heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.

) If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on
this planet, about how many people will have attached earlobes when the planetʹs
population reaches 10,000?
A) 100
B) 400
C) 800
D) 1,000
E) 10,000

A

38

In the year 2500, five male space colonists and five female space colonists (all unrelated to each other)
settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring
randomly mate for generations. All ten of the original colonists had free earlobes, and two were
heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.

If four of the original colonists died before they produced offspring, the ratios of genotypes
could be quite different in the subsequent generations. This would be an example of
A) diploidy.
B) gene flow.
C) genetic drift.
D) disruptive selection.
E) stabilizing selection.

C

39

You are studying three populations of birds. Population A has ten birds, of which one is brown (a
recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30
birds, and three of them are brown.

In which population is the frequency of the allele for brown feathers highest?
A) Population A.
B) Population B.
C) Population C.
D) They are all the same.
E) It is impossible to tell from the information given.

D

40

You are studying three populations of birds. Population A has ten birds, of which one is brown (a
recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30
birds, and three of them are brown.

) In which population would it be least likely that an accident would significantly alter the
frequency of the brown allele?
A) Population A.
B) Population B.
C) Population C.
D) They are all the same.
E) It is impossible to tell from the information given.

B

41

You are studying three populations of birds. Population A has ten birds, of which one is brown (a
recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30
birds, and three of them are brown.

Which population is most likely to be subject to the bottleneck effect?
A) Population A.
B) Population B.
C) Population C.
D) They are all the same.
E) It is impossible to tell from the information given.

A

42

You are maintaining a small population of fruit flies in the laboratory by transferring the
flies to a new culture bottle after each generation. After several generations, you notice that
the viability of the flies has decreased greatly. Recognizing that small population size is
likely to be linked to decreased viability, the best way to reverse this trend is to
A) cross your flies with flies from another lab.
B) reduce the number of flies that you transfer at each generation.
C) transfer only the largest flies.
D) change the temperature at which you rear the flies.
E) shock the flies with a brief treatment of heat or cold to make them more hardy

A

43

If the frequency of a particular allele that is present in a small, isolated population of alpine
plants decreases due to a landslide that leaves an even smaller remnant of surviving plants
bearing this allele, then what has occurred?
A) a bottleneck
B) genetic drift
C) microevolution
D) A and B only
E) A, B, and C

E

44

If the original finches that had been blown over to the Galapagos from South America had
already been genetically different from the parental population of South American finches,
even before adapting to the Galapagos, this would have been an example of
A) genetic drift.
B) bottleneck effect.
C) founderʹs effect.
D) all three of these
E) both A and C

E

45

Over time, the movement of people on Earth has steadily increased. This has altered the
course of human evolution by increasing
A) non-random mating.
B) geographic isolation.
C) genetic drift.
D) mutations.
E) gene flow.

E

46

Gene flow is a concept best used to describe an exchange between
A) species.
B) males and females.
C) populations.
D) individuals.
E) chromosomes.

C

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.

E

48

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.

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.

A

49

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.

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.

D

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

C

51

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

D

52

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).

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.

D

53

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).

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

D

54

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).

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.

A

55

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.

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.

A

56

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.

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.

C

57

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.

) 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.

C

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.

A

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.

E

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.

E

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.

D

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

D

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

E

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

C

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

B

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

C

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

D

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

D

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

C

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.

A

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

B

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.

B

73
card image

What is true of the trait whose frequency distribution in a large population appears above?
It has probably undergone
A) directional selection.
B) stabilizing selection.
C) disruptive selection.
D) sexual selection.
E) random selection

B

74
card image

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) 2 and 3
D) 4 and 5
E) 1, 2, and 3

C

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.

C

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.

E

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

B

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.

E

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.

A

80

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the
gametes produced in the population contain the A1 allele. If the population is in
Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?
A) 0.7
B) 0.49
C) 0.21
D) 0.42
E) 0.09

D

81

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.

A

82

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

E

83

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.

B

84

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.

B