Answer Key Chapter Test B Multiple Choice 1. 2. 3. 4. 5. 6.
a b b d c a
7. 8. 9. 10. 11. 12. 13. 14. 15.
c d c b b d a d b
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Short Answer 16. directional selection 17. Directional selection
occurs when one extreme phenotype is favored by natural selection. 18. The graph would shift back toward the left. The mean value of the number of spines would shift toward plants with lower numbers of spines. 19. 110 20. The peccaries are eating more cacti with fewer spines, so cacti with a greater number of spines are being selected for.
species become extinct during these global events. 23. The oldest mass extinction event occurred about 480 million years ago. The next event occurred about 400 million years ago. The next two occurred about 250 million years ago and 214 million years ago. The last occurred about 56 million years ago. (Allow estimates close to these numbers, because the graph is imprecise.) 24. the theory of punctuated equilibrium 25. Mass extinctions are the result of global catastrophes, during which a large portion of the species on Earth become extinct. These events open up large portions of Earth’s land and/or marine environments. Organisms that survive the mass extinction event may undergo a rapid burst of evolution and diversify to fill the open environments. Global diversity often changes dramatically after a mass extinction event.
21. The five mass extinction
events in the fossil record. 22. Mass extinctions occur
as a result of global catastrophes. These events result in extinction rates than are much higher that the normal background extinction rate. Many
Answer Key
1
CHAPTER
THE EVOLUTION OF POPULATIONS
11
Chapter Test B
Multiple Choice Choose the letter of the best answer. (15 credits) 1. A population of squirrels that contains a
wide range of phenotypes has a a. large amount of genetic variation. b. high allele frequency for most
2. Mutations in the DNA of genes that can
be passed on to offspring
shows a normal distribution. On a graph, this frequency would produce what kind of curve? a. shifted right
c. tall and thin
b. doubled
d. bell-shaped
5. Disruptive selection occurs when
selective pressures favor phenotypes that are a. close to the mean. b. toward one extreme.
a. are more likely with genetic drift.
c. at both extremes.
b. result in increased genetic variation.
d. in a normal distribution.
c. do not occur randomly during
cactus population under pressure from peccaries (wild pigs) and parasitic insects. The dashed line shows the original cactus population. What type of selection does the graph show?
Number of cacti
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3. Figure 11.1 shows the change in a
30
peccaries
parasitic insects
6. Figure 11.2 shows a graph of
reproductive success versus tail feather length for male widowbirds. What type of selection is shown by these data? 2.0 Average nests per male bird
evolution. d. are always harmful to the offspring.
CHAPTER 11 The Evolution of Populations
alleles. c. poor chance of surviving habitat change. d. decreased chance of frequent gene flow.
4. In a population of foxes, tail length
1.5
Shortened Control 1 Control 2 Lengthened
1.0
0.5
0.0
20
FIG. 11.2 10
60
70 80
FIG. 11.1
a. sexual
c. stabilizing
b. disruptive
d. divergent
90 100 110 120 130
Number of spines
a. directional
c. intermediate
b. stabilizing
d. disruptive
Assessment Book McDougal Littell Biology
Tail feather treatment
Chapter Test B
221
CHAPTER TEST B, CONTINUED
population must be
a. gene flow following disruptive
gene flow, no mutations, no natural selection. b. very large, have random mating, high gene flow, many mutations, natural selection. c. small, have nonrandom mating, no gene flow, many mutations, no natural selection. d. very large, have random mating, no gene flow, no mutations, no natural selection.
selection. b. microevolution by reproductive isolation. c. genetic drift through the bottleneck effect. d. speciation triggered by the founder effect. 8. What occurs when some elephants in a
population migrate into another area and join another population? a. genetic drift
c. speciation
b. microevolution
d. gene flow
9. A river has cut a deep canyon that
has separated a population of rodents into two groups. This separation is an example of what type of isolation? a. temporal
c. geographic
b. behavioral
d. founder
10. The evolution of hummingbirds’ beaks
and plants with deep tubes in their flowers is an example of a. convergence.
c. speciation.
b. coevolution.
d. radiation.
11. For a certain population, the actual
frequencies of a genotype did not match the genotype frequencies predicted by the Hardy-Weinberg equation. What can be said about the population?
222
12. To be in Hardy-Weinberg equilibrium, a
the palm trees in an area. This event will most likely lead to
a. very small, have random mating, no
13. In a population of rattlesnakes that
is evolving, which of the following statements is most likely true? a. The rates of gene flow and mutation
are high. b. The population is in Hardy-Weinberg equilibrium. c. Directional selection is probably not occurring. d. Natural selection has no effect on this population. 14. When individuals from two populations
of squirrels can no longer successfully mate with one another, the chance that speciation will occur a. decreases.
c. stays the same.
b. becomes zero.
d. increases
15. The wings of robins and the wings of
dragonflies are examples of
a. Allele frequencies are declining.
a. divergent adaptation.
b. The population is evolving.
b. convergent evolution.
c. No mutations are occurring.
c. adaptive radiation.
d. Gene flow does not occur.
d. punctuated equilibrium.
Chapter Test B
Assessment Book McDougal Littell Biology
Copyright © McDougal Littell/Houghton Mifflin Company.
CHAPTER 11 The Evolution of Populations
7. A tsunami has destroyed almost all of
CHAPTER TEST B, CONTINUED
Short Answer Use the diagram below to answer items 16–20. (5 credits)
20
CHAPTER 11 The Evolution of Populations
Number of cacti
30
10
60
70 80 90 100 110 120 130 Number of spines
FIG. 11.3
16. In a desert environment, cacti are eaten by peccaries, a type of wild pig. What type of
selection is shown in Figure 11.3?
Copyright © McDougal Littell/Houghton Mifflin Company.
17. How does this type of selection occur?
18. What would happen to the graph if the peccaries began eating more of the very spiny
cacti?
19. What is the most common number of spines in the new cactus population?
20. Why are cacti with the most spines becoming more common?
Assessment Book McDougal Littell Biology
Chapter Test B
223
CHAPTER TEST B, CONTINUED
Use the diagram below to answer items 21–25. (5 credits)
Extinction rate (families per million years)
CHAPTER 11 The Evolution of Populations
20
15
10
5
Approximate background extinctions
0 600
400
200
0
Millions of years ago
FIG. 11.4 21. What do the five steepest peaks in Figure 11.4 represent?
23. According to Figure 11.4, when did the five largest mass extinction events occur?
24. What theory has been used to explain the pattern of rapid evolution that often occurs
after a mass extinction event, which is followed by long periods of stability?
25. Explain why mass extinction events are a significant part of the history of life on Earth.
224
Chapter Test B
Assessment Book McDougal Littell Biology
Copyright © McDougal Littell/Houghton Mifflin Company.
22. What causes mass extinctions?