CHAPTER 21—MICROEVOLUTION: GENETIC CHANGES WITHIN
POPULATIONS
MULTIPLE CHOICE
1. A group of interbreeding individuals in a specific geographical location is called a
a.
gene pool.
b.
species.
c.
population.
d.
community.
e.
ecosystem.
2. The development of penicillin-resistant bacteria in the 20th Century represents an example of
a.
punctuated equilibrium
b.
speciation
c.
genetic drift
d.
microevolution
e.
mutation
3. The most accurate DEFINITION of microevolution is
a.
heritable change in the genetics of a population.
b.
natural selection leading to adaptation.
c.
the occurrence of a series of mutation over time.
d.
the origin of new species through natural selection.
e.
the origin of major new forms of life over time.
4. Bacterial resistance to penicillin began to appear
a.
several decades after its first use.
b.
100 years after its first use.
c.
after the drug supply was largely from synthetic sources.
d.
during the AIDS outbreak in the 1980s.
e.
within a few years of its introduction into general use.
5. Characters that exist in two or more discrete states are by definition
a.
quantitative variation.
b.
qualitative variation.
c.
in genetic equilibrium.
d.
showing punctuated equilibrium.
e.
undergoing disruptive selection.
6. Variation that approximates a bell-shaped curve when plotted on a bar graph is
a.
undergoing disruptive selection.
b.
undergoing stabilizing selection.
c.
quantitative variation.
d.
qualitative variation.
e.
in genetic equilibrium.
7. Studies of chromosomal and mitochondrial DNA suggest all of the following EXCEPT that every
locus exhibits some variability in its nucleotide sequence
a.
among individuals from a single
population.
d.
within species in a genus.
b.
between populations of the same species.
e.
within an individual.
c.
between related species.
8. The Hardy-Weinberg formula is valuable for the calculation of changes in
a.
population size.
b.
speciation.
c.
allele frequencies.
d.
mutation.
e.
dimorphism.
9. Natural selection acting on a population may NOT favor
a.
individuals at the left end of the range of variation.
b.
individuals at the right end of the range.
c.
extreme individuals at both ends of the range.
d.
the intermediate individuals within the range.
e.
obligate asexually reproducing organisms.
10. Microevolution can be said to have taken place when
a.
a population experiences a shift in allele frequencies.
b.
a mutation occurs in a population.
c.
several mutations occur in a population.
d.
a feature of an individual animal changes through use or disuse.
e.
when a population has different forms of the same gene.
11. In an isolated population of fruit flies, 4 percent of the individuals have “pink eyes”, a homozygous
recessive condition, and 96 percent have the dominant black eye phenotype. What percentage of the
population are heterozygotes?
a.
32 percent
b.
16 percent
c.
48 percent
d.
88 percent
e.
4 percent
12. The Hardy-Weinberg principle of genetic equilibrium tells us what to expect when a sexually
reproducing population is
a.
decreasing with each generation.
b.
increasing with each generation.
c.
migrating.
d.
evolving.
e.
not evolving.
13. Which of the following will disrupt Hardy-Weinberg equilibrium the least?
a.
directional selection
b.
stabilizing selection
c.
migration
d.
reduction to a small population size
e.
non-random mating
14. Which of the following is a correct expression of the Hardy-Weinberg equation?
a.
p + q = p2 + q2
b.
p2 + 2pq + q2 = 0
c.
p2 + pq − q2 = 1
d.
p2 + 2pq + q2 = 1
e.
p+q = 0
15. If there are two alleles for a gene in a population, and the frequency of the dominant allele (p) is .5,
then the frequency of the recessive allele (q) is
a.
.5.
b.
.025.
c.
.25.
d.
.75.
e.
.05.
16. In the Hardy-Weinberg equation “2pq” represents
a.
the homozygous recessive genotypes.
b.
the heterozygous genotypes.
c.
the homozygous dominant genotypes.
d.
the total pool of alleles for the dominant phenotypes.
e.
the heterozygous phenotypes
17. If the frequency of the recessive allele (q) for a particular gene in a population is .2, what percentage of
the individuals in the population will be heterozygotes for that gene (only two alleles present for that
gene)?
a.
.8
b.
.2
c.
.32
d.
.16
e.
.64
18. In a colony of 100 guinea pigs, 16 show the recessive trait of bristly hair. What is the frequency of the
recessive allele in the population?
a.
.4
b.
.16
c.
.04
d.
.016
e.
.2
19. In a colony of 100 guinea pigs, 16 show the recessive trait of bristly hair. What is the percentage of
heterozygotes in the population?
a.
48 percent
b.
52 percent
c.
36 percent
d.
24 percent
e.
84 percent
20. If we want to know the percentage of particular genotypes within an actual population, assuming
complete dominance and two alleles, the one measurement we have to actually make is of the
frequency of the
a.
heterozygous phenotypes.
b.
heterozygous genotypes.
c.
homozygous dominant genotypes.
d.
dominant phenotypes.
e.
recessive phenotypes.
21. The contribution an individual makes to the gene pool of the next generation relative to the
contributions of other individuals is called
a.
competition.
b.
genetic drift.
c.
relative fitness.
d.
gene flow.
e.
mutation.
22. Microevolution is
a.
the appearance of a life form adapted to a new adaptive zone.
b.
the formation of a new species.
c.
the occurrence of a new mutation.
d.
a change in allele frequencies within a population.
e.
the gradual change in the form of fossils over geological time.
23. A sudden reduction in population size generally results in
a.
extinction.
b.
mutation.
c.
speciation.
d.
genetic drift.
e.
natural selection.
24. The source of new alleles in a population is
a.
natural selection.
b.
mutation.
c.
microevolution.
d.
adaptation.
e.
genetic drift.
25. The only survivors of a colony on Venus are a man and a woman, who happen to be both originally
from the southern Ukraine. Their descendants will show the effect of
a.
genetic drift.
b.
punctuated equilibrium.
c.
excessive mutation.
d.
heterozygote advantage.
e.
frequency-dependent selection.
26. We are sending a small number of dogs to colonize a new planet. Through a random selection process,
we end up only with dachshunds and chihuahuas. The subsequent colony of dogs are all small with
short legs. This is an example of
a.
adaptive radiation.
b.
punctuated equilibrium.
c.
genetic drift.
d.
microevolution.
e.
mutation.
27. Because of fluctuations in the environment, such as depletion of food supply or an outbreak of disease,
a population may periodically experience a rapid and marked decrease in number of individuals,
leading to a form of genetic drift called
a.
a founders effect.
b.
migration.
c.
gene flow.
d.
natural selection.
e.
a genetic bottleneck.
28. The production of random evolutionary changes in small breeding populations is known as
a.
gene flow.
b.
genetic drift.
c.
disruptive selection.
d.
mutation.
e.
natural selection.
29. Which is the LEAST LIKELY result of a genetic bottleneck?
a.
complete elimination of the less common allele
b.
increase in the frequency of the less common allele
c.
allele frequencies identical to the previous generation
d.
decrease in the frequency of an uncommon allele
e.
decrease in the frequency of the most common allele
30. Directional selection favors
a.
intermediate phenotypes.
b.
phenotypes at one end of the distribution.
c.
phenotypic extremes at both ends.
d.
heterozygotes.
e.
homozygotes.
31. Natural selection that shifts the adaptation of an entire populations is
a.
stabilizing selection.
b.
directional selection.
c.
disruptive selection.
d.
artificial selection.
e.
sexual selection.
32. Natural selection results in
a.
adaptation.
b.
a mutation.
c.
a new species.
d.
genetic drift.
e.
stabilizing selection.
33. Changing environmental conditions would most likely cause an existing species to undergo
a.
disruptive selection.
b.
mutation.
c.
directional selection.
d.
stabilizing selection.
e.
paedomorphosis.
34. The founder effect is a type of
a.
natural selection.
b.
mutation.
c.
genetic drift.
d.
gene flow.
e.
adaptation.
35. Which process results in microevolution without any form of natural selection?
a.
genetic drift
b.
mutation
c.
development of new characteristics during an individual’s lifetime
d.
genetic variation
e.
nonrandom mating
36. Evolution can be said to have taken place when
a.
a population experiences a shift in allele frequencies.
b.
a mutation occurs in a population.
c.
several mutations occur in a population.
d.
a feature of an individual animal changes through use or disuse.
e.
a population has different forms of the same gene.
37. If individuals move from one population to another, it may cause a shift in allele frequencies due to
a.
genetic drift.
b.
directional selection.
c.
natural selection.
d.
mutation.
e.
gene flow.
38. Genetic drift will have a progressively larger impact on allele frequencies in a population as
a.
gene flow increases.
b.
population size decreases.
c.
mutation rate decreases.
d.
the number of heterozygous loci increases.
e.
random mating increases.
39. A baby born with wrinkled, poorly-formed skin and blood vessels prone to rupturing can be said to
have inherited a
a.
lethal mutation.
b.
deleterious mutation.
c.
neutral mutation.
d.
advantageous mutation.
e.
partial mutation.
40. When male moose engage in their annual battles, butting heads with their oversized antlers, they are
participating in a process that will lead to
a.
stabilizing selection.
b.
disruptive selection.
c.
directional selection.
d.
intrasexual selection.
e.
intersexual selection.
41. Inbreeding is due primarily to
a.
migration.
b.
non-random mating.
c.
mutation.
d.
natural selection.
e.
adaptive radiation.
42. Concerns about the small size of humpback whale populations led to a collaborative study of their
a.
geographic distribution.
b.
adaptive characteristics.
c.
population growth rates.
d.
environmental changes.
e.
genetic variability.
43. Balanced polymorphism in a population is likely the result of
a.
disruptive selection.
b.
sexual selection.
c.
directional selection.
d.
reproductive isolation.
e.
stabilizing selection.
44. The stable presence of more than one allele for a particular gene in a population is called
a.
balanced polymorphism.
b.
mixed gene pool.
c.
mutation pressure.
d.
genetic drift.
e.
competition.
45. Sometimes the most abundant color form of an animal is preyed upon more extensively than less
common forms. This illustrates the phenomenon of
a.
stabilizing selection.
b.
directional selection.
c.
disruptive selection.
d.
frequency dependent selection.
e.
genetic drift.
46. People with the disease known as sickle-cell anemia are often better able to survive malaria because of
a.
balanced polymorphism.
b.
heterozygote advantage.
c.
frequency dependent selection.
d.
disruptive selection.
e.
stabilizing selection.
47. Mutations that confer no apparent selective advantage or disadvantage in a particular environment are
said to be selectively
a.
random.
b.
deleterious.
c.
neutral.
d.
benign.
e.
stabilizing.
48. The distribution of the genetic disorder called sickle-cell anemia is correlated with the distribution of
malaria in tropical countries. This is an example of
a.
heterozygote advantage.
b.
frequency-dependent selection.
c.
a genetic bottleneck.
d.
genetic drift.
e.
evolutionary convergence.
49. The decline in the occurrence of sickle-cell anemia in the American population is most likely the result
of
a.
a lower mutation rate in the United States than in Africa.
b.
the advantage of both homozygous forms over the heterozygous form.
c.
the development of appropriate medical treatment for the sickle-cell condition in the
United States.
d.
a decline in the occurrence of malaria in the United States.
e.
the absence of mosquitoes.
50. The difference in the appearance of the male and the female of the same species is called
a.
polymorphism.
b.
sexual dimorphism.
c.
the dioecious condition.
d.
sexual selection.
e.
a primary sexual characteristic.
51. In frequency-dependent selection, highest mortality can be expected in
a.
the most abundant genotype.
b.
the least abundant genotype.
c.
the least well-adapted genotype.
d.
heterozygous genotypes.
e.
homozygous recessive genotypes.
52. Under what circumstance might measuring the frequency of homozygous recessive genotypes lead to
erroneous predictions of allele frequencies in a population?
a.
the population is under Hardy-Weinberg equilibrium
b.
the population is affected by heterozygote advantage
c.
the population has undergone genetic drift in the past
d.
the population is in a stable phase of punctuated equilibrium
e.
the population is affected by frequency-dependent selection
53. According to the modern synthetic theory of evolution, the accumulation of mutations over time
results in
a.
microevolution.
b.
adaptation.
c.
an increase in genetic variation.
d.
speciation.
e.
macroevolution.
54. Which of the following evolution-related events is in the correct cause-and-effect sequence?
a.
mutation → variation → natural selection → adaptation → speciation
b.
variation → adaptation → mutation → natural selection → speciation
c.
speciation → adaptation → variation → mutation → natural selection
d.
mutation → speciation → adaptation → variation → natural selection
e.
natural selection → variation → mutation → adaptation → speciation
55. Any product of natural selection that increases the relative fitness of an organism in its environment is
called
a.
mutation.
b.
adaptive trait.
c.
adaptation.
d.
speciation.
e.
variation.
56. Sometimes an allele that has no phenotypic effect can spread through a population by means of
a.
a selective sweep
b.
genetic recombination
c.
disruptive selection
d.
frequency-dependent selection
e.
directional selection
Select the Exception
57. Four of the five processes listed below will disrupt Hardy-Weinberg equilibrium. Select the exception.
a.
non-random mating
b.
natural selection
c.
migration
d.
punctuated equilibrium
e.
genetic drift
58. Four of the five population attributes can be calculated with the Hardy-Weinberg equation. Select the
exception.
a.
the frequency of heterozygotes
b.
the frequency of homozygous dominant genotypes
c.
the frequency of a dominant allele
d.
the frequency of a recessive allele
e.
the frequency of mutation
59. Four of the five processes below are agents of microevolutionary change. Select the exception.
a.
mutation
b.
genetic drift
c.
natural selection
d.
random mating
e.
gene flow
440
60. Four of the five processes below are components of natural selection. Select the exception.
a.
genetic drift
b.
overproduction of offspring
c.
limitations in vital resources
d.
genetic variation
e.
differential reproductive success
61. Which of the following is not an agent of microevolutionary change?
a.
mutation
b.
gene flow
c.
random mating
d.
genetic drift
e.
natural selection
MATCHING
Match each of the following definitions with the correct agent.
a.
Gene flow
b.
Nonrandom mating
c.
Genetic drift
d.
Mutation
e.
Natural selection
62. A heritable change in DNA
63. Change in allele frequencies as individuals join a population and reproduce
64. Random changes in allele frequencies caused by chance events
65. Differential survivorship or reproduction of individuals with different genotypes
66. Choice of mates based on their phenotypes and genotypes
Match the Hardy Weinberg factor with the correct genetic designation.
a.
Frequency of heterozygotes
b.
Frequency of the dominant allele
c.
Frequency of the recessive allele
d.
The total gene pool for a gene with two alleles
e.
Frequency of homozygous recessive genotypes
f.
Frequency of homozygous dominant genotypes
67. p
68. q
69. q2
70. p2
71. 2pq
72. p + q
SHORT ANSWER
73. Distinguish between quantitative and qualitative variation.
74. If you wanted to calculate the frequencies of the two different alleles for a particular gene in a
population, what data would you have to gather and how would you use it?
75. How does gene flow introduce novel genetic variants into populations?
76. How could parasitism by wasps and feeding by birds result in a higher percentage of galls of medium
size rather than small or large galls, or an even percentage of all sizes of galls, made by a gall-making
fly?
77. How can an allele that confers no selective advantage spread through a population?
MODIFIED TRUE/FALSE
If the statement is true, answer “T“. If the statement is false, answer “F” and make it correct by
changing the underlined word(s) and writing the correct word(s) in the answer blank(s).
78. Natural selection results in organisms perfectly adapted to their environments.
79. Natural selection quickly eliminates harmful alleles from the population.
80. Genetic drift can eliminate alleles from a population more quickly than natural selection
81. When multiple color forms of an organism exist in a population, the least abundant form is likely to
increase in frequency.
82. Bacteria readily develop immunity to many forms of antibiotics.
83. In an unchanging environment, a well-adapted population is likely to experience no natural selection
of any kind.
84. Genetic drift is non-selective and therefore does not contribute to microevolution.
85. The reason why some specialty breeds of dogs are more prone to genetic disease is because of genetic
drift.
86. Small populations on islands can be said to have experienced a form of genetic drift called the
founders effect.
87. Phenotypic variation cannot be passed on from one generation to the next.
88. Intermediate forms are often absent in characters showing qualitative variation.
89. Genetic variation can originate both from the production of new alleles and from the arrangement of
existing alleles.
90. New traits arise from scratch through the formation of a new gene.
ESSAY
91. How can organisms with the same phenotype have different genotypes and vice versa, and what is the
significance?
92. If you were planning the colonization of a distant planet, what would you do to insure that the
population remained genetically healthy for a long time?