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
Copyright by McDougal Littell, a division of Houghton Mifflin Company
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
THE EVOLUTION OF POPULATIONS
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
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?
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
Shortened Control 1 Control 2 Lengthened
FIG. 11.2 10
90 100 110 120 130
Number of spines
Assessment Book McDougal Littell Biology
Tail feather treatment
Chapter Test B
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
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
10. The evolution of hummingbirds’ beaks
and plants with deep tubes in their flowers is an example of a. convergence.
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?
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.