AP BIO CHAPTER 21 Flashcards

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

Which variable is likely to undergo the largest change in value resulting from a mutation that
introduces a new allele into a population at a locus for which all individuals formerly had been
fully homozygous?
A) average heterozygosity
B) nucleotide variability
C) geographic variability
D) average number of loci

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's survival was strongly influenced by the depth and strength of its beak as the
drought persisted.
C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than
seen in the previous generation.
D) The frequency of the strong-beak alleles increased in each bird as the drought persisted.

The higher the proportion of loci that are "fixed" in a population, the lower is that population's
A) nucleotide variability only.
B) chromosome number only.
C) average heterozygosity only.
D) nucleotide variability, average heterozygosity, and chromosome number.
E) nucleotide variability and average heterozygosity.

Rank the following one-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 third position of an exonic codon
3. substitution mutation at the second 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

Which of the following 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 lower average heterozygosity.

How many of these statements regarding populations are true?
1. Mature males and females of a population can interbreed with each other.
2. Populations are sometimes geographically isolated from other populations.
3. Biological species are made up of populations.
4. Members of a population tend to be genetically more similar to each other than to members of
other populations.
5. Populations have genomes, but not gene pools.
A) Only one of these statements is true.
B) Two of these statements are true.
C) Three of these statements are true.
D) Four of these statements are true.
E) All five of these statements are true.

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus
A) the allele's frequency should not change from one generation to the next, but its
representation in homozygous and heterozygous genotypes may change.
B) natural selection, gene flow, and genetic drift are acting equally to change an allele's
frequency.
C) this means that, at this locus, two alleles are present in equal proportions.
D) the population itself is not evolving, but individuals within the population may be evolving.

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is
necessary because
A) the population is diploid.
B) heterozygotes can come about in two ways.
C) the population is doubling in number.
D) heterozygotes have two alleles.

In the formula for determining a population’s genotype frequencies, the pq in the term 2pq is
necessary because
A) the population is diploid.
B) heterozygotes can come about in two ways.
C) the population is doubling in number.
D) heterozygotes have two alleles.

Hardy-Weinberg equilibrium must occur in populations where
A) an allele remains fixed.
B) no genetic variation exists.
C) natural selection is not operating.
D) All three of the responses above are correct.
E) Only two of the responses above are correct.

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the
frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this
allele?
A) 0.09
B) 0.49
C) 0.9
D) 9.0
E) 49.0

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 that are heterozygous for this
allele?
A) 0.002
B) 0.020
C) 0.04
D) 0.16
E) 0.32

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 frequency of individuals with AA genotype?
A) 0.20
B) 0.32
C) 0.42
D) 0.81
E) Genotype frequency cannot be determined from the information provided.

You sample a population of butterflies and find that 56% are heterozygous at a particular
locus. What should be the frequency of the recessive allele in this population?
A) 0.07
B) 0.08
C) 0.09
D) 0.70
E) Allele frequency cannot be determined from this information.

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) 0.64
C) 0.75
D) 0.80

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.

Although each of the following has a better chance of influencing gene frequencies in small
populations than in large populations, which one most consistently requires a small population as
a precondition for its occurrence?
A) mutation
B) nonrandom mating
C) genetic drift
D) natural selection
E) gene flow

Evolution
A) must happen, due to organisms' innate desire to survive.
B) must happen whenever a population is not well adapted to its environment.
C) can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.
D) requires the operation of natural selection.
E) requires that populations become better suited to their environments.

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

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

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

What is true of natural selection?
A) Natural selection is a random process.
B) Natural selection creates beneficial mutations.
C) The only way to eliminate harmful mutations is through natural selection.
D) Mutations occur at random; natural selection can preserve and distribute beneficial mutations.
E) Mutations occur when directed by the good of the species; natural selection edits out harmful
mutations and causes populations to adapt to the beneficial mutations.

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.

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 the first and second responses are correct.

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

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

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 birds' diets; no vertebrates
are known to synthesize carotenoid pigments. Thus, the brighter red the male's 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) Three of the statements are correct.
E) Two of the statements are correct.

During breeding season, one should expect female house finches to prefer to mate with males
with the brightest red feathers. Which of the following terms are appropriately applied to this
situation?
A) sexual selection
B) mate choice
C) intersexual selection
D) Three of the responses are correct.
E) Two of the responses are correct.

Adult male humans generally have deeper voices than do adult female humans, which is 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) stabilizing selection was occurring in these species concerning larynx size.
D) selection was acting more directly upon genotype than upon phenotype.

Which of the following is most likely to produce an African butterfly species in the wild
whose members have one of two strikingly different color patterns?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

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

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's
diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this
harmful allele in a population's gene pool?
A) heterozygote advantage
B) stabilizing selection
C) diploidy
D) balancing selection

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

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) No selection would operate because the population is in Hardy-Weinberg equilibrium.

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.

The same gene that causes various coat patterns in wild and domesticated cats also causes a
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.

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. The actual
forelimbs of these mammals do not seem to be optimally arranged 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) in many cases, phenotype is not merely determined by genotype, but by the environment as
well.
C) 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.
D) natural selection is generally limited to modifying structures that were present in previous
generations and in previous species.

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 population's evolution is limited by historical constraints.
C) Adaptations are often compromises.
D) Evolution can be influenced by environmental change.