39) A rabbit population consists of animals that are either very dark on top or very light on top.
The color pattern is not related to sex. No rabbit shows intermediate coloration (medium
darkness). This pattern might result from
A) disruptive selection.
B) directional selection.
C) stabilizing selection.
D) sexual selection.
40) Large antlers in male elk, which are used for battles between males, are a good example of a
trait favored by
A) intersexual selection.
B) intrasexual selection.
C) disruptive selection.
D) stabilizing selection.
41) Mate-attracting features such as the bright plumage of a male peacock result from
A) intersexual selection.
B) intrasexual selection.
C) disruptive selection.
D) stabilizing selection.
42) A woman struggling with a bacterial illness is prescribed a month’s supply of a potent
antibiotic. She takes the antibiotic for about two weeks and feels much better. Should she save
the remaining two-week supply, or should she continue taking the drug?
A) She should save the drug for later, because if she keeps taking it the bacteria will evolve
resistance.
B) She should save the drug for use the next time the illness strikes.
C) She should save the drug because antibiotics are in short supply and she may need it to defend
herself against a bioterrorism incident.
D) She should continue taking the drug until her immune system can completely eliminate the
infection. Otherwise, some bacteria may remain in her system, and they will probably be
resistant.
43) If you were just diagnosed with a serious bacterial disease, which of these would predict the
most positive outcome for treatment? The disease was acquired
A) in a hospital, where most of the bacteria are probably already weakened by antibiotics in the
environment.
B) in a livestock barn where the animals have been treated with antibiotics.
C) in a big city where antibiotics are routinely prescribed by doctors.
D) in a remote, sparsely populated area where the bacteria have not been exposed to antibiotic
drugs.
44) Which of the following would most quickly be eliminated by natural selection?
A) a harmful allele in an asexual, haploid population
B) a harmful recessive allele in a sexual, diploid population
C) a harmful recessive allele in a sexual, polyploid population
D) any harmful allele, regardless of the system of inheritance in a population
45) The sickle-cell allele produces a serious blood disease in homozygotes. Why doesn’t natural
selection eliminate this allele from all human populations?
A) Natural selection is a positive force, so it does not eliminate alleles.
B) In populations where endemic malaria is present, heterozygotes have an important advantage:
They are resistant to malaria and therefore are more likely to survive and produce offspring that
carry the allele.
C) Mutations keep bringing the allele back into circulation.
D) Natural selection occurs very slowly, but elimination of the sickle-cell allele is expected to
occur soon.
46) Frequency-dependent selection, as seen in the case of the scale–eating fish in Lake
Tanganyika, tends to
A) eliminate rare alleles and favor whichever allele is initially most frequent.
B) maintain two phenotypes in a dynamic equilibrium in a population.
C) produce random changes in allele frequencies.
D) stimulate new mutations.
47) Tay-Sachs is inherited as an autosomal recessive allele. Homozygous individuals die within
the first few years of life. However, there is some evidence that heterozygous individuals are
more resistant to tuberculosis. Which of the following statements about Tay-Sachs is true?
A) The allele for Tay-Sachs is selected against.
B) This situation is an example of heterozygote advantage if tuberculosis is present in a
population.
C) This situation is an example of disruptive selection.
D) Heterozygotes will be more fit than either homozygote regardless of environmental
conditions.
48) Some of your DNA may not code for any protein and has no known function in gene
regulation; it is sometimes referred to as “junk” DNA. How do nucleotide sequences of “junk
DNA” evolve?
A) They evolve through natural selection.
B) They evolve through genetic drift and other chance processes.
C) They evolve to be more useful by taking on new functions.
D) They evolve by gradually being eliminated from the gene pool.
49) Mothers and teachers often say they need another pair of eyes on the backs of their heads.
And another pair of hands would come in handy in many situations. You can imagine that these
traits would have been advantageous to our early hunter-gatherer ancestors as well. According to
sound evolutionary reasoning, what is the most likely explanation for why humans do not have
these traits?
A) Because they actually would not be beneficial to the fitness of individuals who possessed
them. Natural selection always produces the most beneficial traits for a particular organism in a
particular environment.
B) Because every time they have arisen before, the individual mutants bearing these traits have
been killed by chance events. Chance and natural selection interact.
C) Because these variations have probably never appeared in a healthy human. As tetrapods, we
are pretty much stuck with a four-limbed, two-eyed body plan; natural selection can only edit
existing variations.
D) Because humans are a relatively young species. If we stick around and adapt for long enough,
it is inevitable that the required adaptations will arise.
50) In a large population of plants, notches in the leaves are caused by a dominant allele N and
lack of notches by a recessive allele n. Over many generations the proportion of plants in the
population with notched leaves increases. What is the most likely cause?
A) Dominant alleles generally increase in frequency over time.
B) The recessive alleles were all masked by the dominant alleles.
C) Directional selection favored plants with notched leaves.
D) Genetic drift caused a steady movement toward a greater proportion of plants with notched
leaves.
51) A population of butterflies has an allele B for big spots on the wings and b for small spots on
the wings. The table below provides data about this population.
Genotype BB Bb bb
Number of butterflies 300 400 300
Genotype frequency 0.3 0.4 0.3
Regarding these data about the butterfly population, which of the following statements is
correct?
A) The population is in Hardy-Weinberg equilibrium because the number of B alleles is equal to
the number of b alleles.
B) The population is in Hardy-Weinberg equilibrium because half of the heterozygotes are B and
half are b.
C) The population is not in Hardy-Weinberg equilibrium because p2 and 2pq are different.
D) The population is not in Hardy-Weinberg equilibrium because the genotype frequency of bb
is greater than it would be in equilibrium.
52) A group of dog breeders is trying to design and develop an ideal dog. They want a dog with a
gentle disposition, black fur, long ears, short legs, and a strong sense of smell. Which of the
following comments from fellow dog breeders represents the biggest challenge they are likely to
face?
A) There are breeds with long ears and breeds with short leg, but no breeds with both.
B) There does not seem to be any genetic variation in sense of smell.
C) Artificial selection is artificial and cannot change the genetics of a breed like natural
selection.
D) Most dogs with black fur have long legs.
53) A farmer decides to go into the business of raising trout for tourists who enjoy fishing. She
builds six trout ponds and stocks each of them with trout from genetically identical stock. Her
friends tell her that because she started each pond with just a few trout, she has created a
bottleneck effect and her trout populations are likely to become genetically different rapidly.
Which of the following statements about her trout is likely true?
A) Because they are all genetically alike, they will all remain alike even though the ponds are
different.
B) Because each population started off with just a few individuals, every mutation that occurs
will have a huge impact on the population, so they are likely to evolve in different directions
quickly.
C) Because the ponds are different and the populations are likely to experience different
mutations, the populations will likely diverge evolutionarily, but only over many generations.
D) The increase in genetic diversity caused by sexual reproduction will promote evolutionary
divergence over time.
54) Brown-eye genes are dominant over blue-eye genes. What is the best explanation for the fact
that all the blue-eye alleles have not disappeared in the human population?
A) Some blue alleles are always hidden in heterozygotes.
B) The population is likely in Hardy-Weinberg equilibrium for that locus.
C) Brown-eyed people sometimes have a blue-eyed parent.
D) People with brown eyes tend to choose mates with brown eyes, and blue-eyed people tend to
choose mates with blue eyes.
55) Which of the following statements about adaptation is true?
A) An individual that has learned how to survive cold winters has become adapted to the cold.
B) A population that has an increase in frequency of alleles for thicker fur has become adapted to
the cold.
C) Adaptation results when cold temperatures cause mutations for longer fur.
D) Adaptation is possible when all the alleles in a gene pool are the same.
56) Some butterflies can ingest toxic chemicals from the milkweed plants they feed on and then
can store those chemicals in their body. Because toxins stored in the butterflies are toxic to birds,
the birds avoid eating the butterflies. Which of the following is the best explanation for this
situation?
A) Butterflies that stored the chemicals were never eaten by predators, so those butterflies
survived.
B) Butterflies developed a mutation that led them to be able to store the chemical because they
needed to avoid being eaten.
C) Milkweed plants wanted the butterflies to ingest the chemical so they would no longer feed on
the plant, but the butterflies fooled the milkweed by storing the toxic chemicals.
D) Any butterfly allele that allowed milkweed toxin storage would be likely to persist because
butterflies that had it were more likely to survive.
57) Which of the following statements regarding fins on fishes is true?
A) Fins evolved so that fish could swim better.
B) Fins came about because animals couldn’t live in water without them.
C) Fins are an adaptation that aid in swimming.
D) Fins resulted from a mutation caused by a movement from land to water.
58) A news article discussing the evolution of domestic dogs from wolves included this
statement: “On its way from pack-hunting carnivore to fireside companion, dogs learned to
love—or at least live on—wheat, rice, barley, corn, and potatoes.” What is a more scientifically
accurate way to state what happened with dogs?
A) Dogs mutated to be able to eat wheat, rice, barley, corn, and potatoes.
B) Some wolves may have had variants in their digestion that allowed them to eat wheat, rice,
barley, corn, and potatoes and so were able to survive with humans.
C) Being around humans represented an advantage, so wolves were able to take advantage of
that by changing their digestion to be able to eat wheat, rice, barley, corn, and potatoes.
D) Dogs were created at the same time as wolves.
13.2 Art Questions
1) According to this figure, which pair of organisms shares the most recent common ancestor?
A) lungfishes and amphibians
B) amphibians and lizards
C) mammals and crocodiles
D) lizards and ostriches
2) Which statement best describes the mode of selection depicted in the figure?
A) stabilizing selection, changing the average color of the population over time
B) directional selection, favoring the average individual
C) directional selection, changing the average color of the population over time
D) disruptive selection, favoring the average individual
3) The change in curves in the graph represents
A) a decrease in genetic variation in a population of mice.
B) the appearance of a new allele for darker color in a population of mice.
C) a shift in the range of genetic variation in a population of mice.
D) a lack of genetic variation for light fur color in the original population of mice.
13.3 Scenario Questions
After reading the paragraph below, answer the questions that follow.
Desert pupfish live in springs of the American Southwest. Today there are about 30 species of
pupfish, but they all evolved from a common Pleistocene ancestor. The southwestern United
States was once much wetter than it is now, and the Pleistocene pupfish flourished over a wide
geographic area. Over thousands of years, however, the Sierra Nevada mountain range was
pushed upward by geological forces, blocking rainfall from the Pacific Ocean. As the large lakes
dried up, small groups of pupfish remained in springs and pools fed by groundwater seepage.
Now, although many of these small springs still have pupfish, each population, through
evolution, has become very different from populations of pupfish in other springs.
1) Which of the following statements represents a probable explanation for differences among
pupfish populations?
A) The frequency of genotypes reached equilibrium.
B) New genes entered the population through migration.
C) The isolated populations had restricted gene pools.
D) Each new species contains all the original genotypes of the larger populations.
2) The variation in gene pools among the 30 pupfish populations occurred through an
evolutionary mechanism called
A) the bottleneck effect.
B) directional selection.
C) random mating.
D) Hardy-Weinberg equilibrium.
3) If, in one population of pupfish all of the individuals have a blood pigment that is
extraordinarily effective at carrying oxygen, but this trait is not seen in any of the other
populations, what likely happened?
A) Because oxygen was low where these pupfish lived, a new allele for an effective blood
pigment arose.
B) This population was lucky to have an individual with a random mutation for an effective
blood pigment, and the frequency of this allele was increased in subsequent generations through
natural selection.
C) The ancestral population probably had this type of blood pigment, but it was lost through
genetic drift in the other 29 populations.
D) The other populations did not need this pigment, so they did not evolve it.