1. Biology
Ch. 16 Review

2. Which of the following statements describe what all members of a population share?
They are temporally isolated from each other.
They are geographically isolated from each other.
They are members of the same species.
They have identical genes.

3. relative frequency. phenotype. genotype. gene pool.
All the genes of all members of a particular population make up the population’s
relative frequency.
phenotype.
genotype.
gene pool.

4. Which statement below about gene pools is typically true?
They contain two or more alleles for each inheritable trait.
They contain only dominant alleles.
They belong to two or more interbreeding species.
The relative frequencies of the alleles never change.

5. If an allele makes up one fourth of a population’s alleles for a given trait, its relative frequency is
100 percent.
75 percent.
25 percent.
4 percent.

6. Interbreeding among members of a population results in
different types of alleles in the gene pool.
changes in the relative frequencies of alleles in the gene pool.
no changes in the relative frequencies of alleles in the gene pool.
an absence of genetic variation in the population.

7. In a population, the sum of the relative frequencies of all alleles for a particular trait is
equal to 100 percent.
equal to the number of alleles for the trait.
constantly changing.
dependent on the number of alleles.

8. A change in a sequence of DNA is called a
recombination.
polygenic trait.
single-gene trait.
mutation.

9. The two main sources of genetic variation are
genotypes and phenotypes.
gene shuffling and mutations.
single-gene traits and polygenic traits.
directional selection and disruptive selection.

10. In many kinds of organisms, inheritable differences are due mostly to
mutations during gamete formation.
polygenic traits.
gene shuffling during gamete formation.
the effects of radiation.

11. Gene shuffling includes the independent movement of chromosomes during meoisis as well as
mutations from radiation.
changes in the frequencies of alleles.
crossing-over.
mutations from chemicals.

12. In a particular population, sexual reproduction can produce
mutations.
many different phenotypes.
new allele frequencies.
meiosis.

13. The gene shuffling that occurs as part of sexual reproduction
changes the gene pool’s allele frequencies.
does not change the gene pool’s allele frequencies.
keeps the phenotypes consistent.
is caused by radiation or chemicals.

14. A single-gene trait that has two alleles and that shows a simple dominant-recessive pattern will result in
one phenotype.
two phenotypes.
four phenotypes.
millions of phenotypes.

15. An example of a single-gene trait is
widow’s peak in humans.
weight of human infants at birth.
height in humans.
beak size in the Galápagos finches.

16. The number of phenotypes produced for a given trait depends upon
the number of genes that control the trait.
which form of the trait is dominant.
the relative frequencies of the various alleles.
the relationship of allele frequencies to Mendelian ratios.

17. The phenotypes for a typical polygenic trait can often be expressed as
a bar graph.
a bell-shaped curve.
Mendelian ratios.
allele frequencies.

18. Compared to a polygenic trait, a single-gene trait tends to have
fewer phenotypes.
more phenotypes.
the same number of phenotypes.
phenotypes that form a bell-shaped curve.

19. A polygenic trait can have
many possible genotypes, but few possible phenotypes.
many possible genotypes, producing many possible phenotypes.
fewer phenotypes than most single-gene traits.
fewer genotypes than most single-gene traits.

20. Natural selection acts directly on
alleles.
genes.
phenotypes.
mutations.

21. Which of the following is NOT a way in which natural selection affects the distribution of phenotypes?
directional selection
stabilizing selection
disruptive selection
chance events

22. When individuals at only one end of a bell curve of phenotype frequencies have high fitness, the result is
directional selection.
stabilizing selection.
disruptive selection.
genetic drift.

23. When individuals with an average form of a trait have the highest fitness, the result is
not predictable.
disruptive selection.
directional selection.
stabilizing selection.

24. directional selection disruptive selection stabilizing selection
In a population of finches in which one group of birds has a short, parrotlike beak and another group has a long, narrow beak, what process has probably occurred?
directional selection
disruptive selection
stabilizing selection
genetic drift

25. If a mutation introduces a new skin color in a lizard population, which factor might determine whether the frequency of the new allele will increase?
how many other alleles are present
whether the mutation makes some lizards more fit for their environment than other lizards
how many phenotypes the population has
whether the mutation was caused by nature or by human intervention

26. In genetic drift, allele frequencies change because of
mutations.
chance.
natural selection.
genetic equilibrium.

27. Which of the following events do biologists consider a random change?
directional selection
speciation
disruptive selection
genetic drift

28. Genetic drift tends to occur in populations that
are very large.
are small.
are formed from new species.
have unchanging allele frequencies.

29. The type of genetic drift that follows the colonization of a new habitat by a small group of individuals is called
the Hardy-Weinberg principle.
the founder effect.
directional selection.
stabilizing selection.

30. One similarity between natural selection and genetic drift is that both events
are based completely on chance.
begin with one or more mutations.
involve a change in a population’s allele frequencies.
take place only in very small groups.

31. The situation in which allele frequencies of a population remain constant is called
evolution.
genetic drift.
genetic equilibrium.
natural selection.

32. One of the conditions required to maintain genetic equilibrium is
natural selection.
mutations.
nonrandom mating.
no movement into or out of the population.

33. The genetic equilibrium of a population can be disturbed by each of the following EXCEPT
nonrandom mating.
movement into and out of the population.
a large population size.
mutations.

34. The allele frequencies of a population are more likely to remain unchanged if
the population size is reduced.
frequent movement into and out of the population occurs.
all mating is random.
the mutation rate increases.

35. According to the Hardy-Weinberg principle, genetic equilibrium would be more likely in a population of mice if
the population size rapidly decreases.
mutation rates within the population rise.
no natural selection takes place.
there is frequent movement into and out of the population.

36. Which factor would most likely disrupt genetic equilibrium in a large population?
the production of large numbers of offspring
mating that is not random
the absence of movement into and out of the population
the absence of mutations

37. The separation of populations by barriers such as rivers, mountains, or bodies of water is called
temporal isolation.
geographic isolation.
behavioral isolation.
genetic equilibrium.

38. A factor that is necessary for the formation of a new species is
reproduction at different times.
geographic barriers.
different mating behaviors.
reproductive isolation.

39. What situation might develop in a population having some plants whose flowers open at midday and other plants whose flowers open late in the day?
behavioral isolation
geographic isolation
temporal isolation
genetic drift

40. The geographic isolation of two populations of a species tends to increase differences between their gene pools because it
prevents interbreeding between the populations.
prevents interbreeding within each population.
causes temporal isolation of the two populations.
increases differences in courtship behavior.

41. Although they often live in the same habitat, the American toad breeds earlier in the spring than the Fowler’s toad does. What can be inferred from this information?
The two species do not interbreed because of geographic isolation.
The two species do not interbreed because of temporal isolation.
The two species interbreed throughout the spring season.
The American toad will cause the extinction of the Fowler’s toad.

42. Which is the first step that occurred in the speciation of the Galápagos finches?
establishing genetic equilibrium
behavioral isolation
ecological competition
arrival of the founding population

43. The Galápagos finch species are an excellent example of
speciation.
genetic equilibrium.
stabilizing selection.
selection on single-gene traits.

44. What did Peter and Rosemary Grant learn about mate choice from the Galápagos finches?
Phenotype plays no role in mate choice.
Finches prefer mates with beaks similar in size to their own.
Finches prefer mates with smaller beaks than their own.
Finches prefer mates with larger beaks than their own.

45. In Rosemary and Peter Grant’s study of the Galápagos finches, what process was encouraged by ecological competition during the dry season?
stabilizing selection
disruptive selection
directional selection
genetic drift

46. Which statement about evolution in the Galápagos finches is true?
Natural selection on beak size and shape is driven by available food.
Stabilizing selection has favored an intermediate beak type for all of the finches.
Mate choice likely plays no role in the finches’ evolution.
None of the finch species is reproductively isolated.

47. Because all members of a population can interbreed, biologists often study their genes as a single group.
True
False

48. In a gene pool, as the relative frequency of one allele for a trait increases, the relative frequencies of other alleles for that trait decrease.
True
False

49. Most inheritable differences are due to mutations that occur during the production of gametes.
True
False

50. Mutations do not always affect an organism’s genotype—its physical, behavioral, and biochemical characteristics.
True
False

51. A polygenic trait is controlled by one gene.
True
False

52. On a graph, the distribution of phenotypes for a single-gene trait tends to form a bell-shaped curve.
True
False

53. Natural selection on single-gene traits can lead to changes in allele frequencies.
True
False

54. In a population of snakes with a range of body lengths, if the longest individuals have the highest fitness, disruptive selection is likely to occur.
True
False

55. In small populations, an allele can become more or less common simply by chance.
True
False

56. Genetic drift may occur when a small group of individuals colonize a new habitat.
True
False

57. When mutations introduce new alleles into a population, genetic variation is disrupted.
True
False

58. In a population of birds, if females prefer males with long tails, the population violates the condition of directional selection described by the Hardy-Weinberg principle.
True
False

59. In the type of reproductive isolation called behavioral isolation, two populations are separated by barriers such as rivers or mountains.
True
False

60. Two populations that have overlapping ranges can remain reproductively isolated through behavioral isolation or temporal isolation from each other.
True
False

61. The first step of the speciation of the Galápagos finches likely was the arrival of founders from South America.
True
False