CHAPTER 7 Evolution and AdaptationThe process of evolution depends on genetic variation.MULTIPLE CHOICE1.Topic: The process of evolution depends on genetic variation.Level: easyDifferent forms of a particular gene are known asa. chromosomes.b. alleles.c. polygenic.d. pleiotropic.Answer: b2.Topic: The process of evolution depends on genetic variation.Level: easyA trait that is determined by multiple genes is referred to asa. polygenic.b. pleiotropic.c. homozygous.d. heterozygous.Answer: a3.Topic: The process of evolution depends on genetic variation.Level: mediumChickens with the dominant allele at the frizzle gene produce curly feathers, have very high body temperature, and lay few eggs.This is an example ofa. polygenic traits.b. pleiotropy.c. epistasis.d. random assortment.Answer: b4. Topic: The process of evolution depends on genetic variation.Level: mediumTwo of the genes that affect coat color in horses are the extension gene and the cream dilution gene. The dominant E allele at the extension gene generates black coats, while the recessive e allele produces red coats.The coat color caused by the extension gene is not altered if the horse is a homozygote for the C allele at the cream dilution gene.However, if the horse is a homozygote for the C Cr allele at the cream dilution gene, it will have a white coat regardless of the extension genotype.This interaction between the extension and the cream dilution gene is an example ofa. pleiotropy.b. epistasis.c. codominance.d. random assortment.Answer: b5. Topic: The process of evolution depends on genetic variation.Level: difficultWhich of the following types of allele would we expect to have the lowest frequency in a population?a. beneficial recessive alleleb. beneficial dominant allelec. harmful recessive alleled. harmful dominant alleleAnswer: d6. Topic: The process of evolution depends on genetic variation.Level: mediumConsider a gene that affects fur color in mice.This gene has two alleles, A and a.If AA mice have white fur, Aa mice have gray fur, and aa mice have black fur, how would we describe the effect of these alleles?a. A is dominant and a is recessive.b. A is recessive and a is dominant.c. A and a are codominant.d. A and a are epistatic.Answer: c7. Topic:The process of evolution depends on genetic variation.Level: mediumConsider a gene that affects number of seeds in a plant.This gene has two alleles, G and g.If GG plants produce 50 seeds, Gg plants produce 50 seeds, and gg plants produce 25 seeds, how would we describe the effect of these alleles?a. G is dominant and g is recessive.b. G is recessive and g is dominant.c. G and g are codominant.d. G and g are polygenic.Answer: a8. Topic:The process of evolution depends on genetic variation.Level: easyWhat term refers to the alleles of all of the genes of every individual in a population?a. polygenicb. heterozygousc. gene poold. random assortmentAnswer: c9. Topic:The process of evolution depends on genetic variation.Level: easyWhat process creates new alleles in a population?a. random assortmentb. mutationc. recombinationd. epistasisAnswer: b10. Topic:The process of evolution depends on genetic variation.Level: difficultFor mutations that enter a population of a diploid organism, which type of mutation is most likely to be affected by natural selection when it first appears?a. synonymous mutationb. nonsynonymous recessive mutationc. nonsynonymous dominant mutationd. All are equally likely to be affected by natural selection.Answer: c11. Topic:The process of evolution depends on genetic variation.Level: easyThe shuffling of genes that occurs when DNA is copied during meiosis is known asa. recombination.b. mutation.c. random assortment.d. epistasis.Answer: a12. Topic:The process of evolution depends on genetic variation.Level: easyWhat term describes makingnew combinations of alleles using existing genetic variation across many chromosomes?a. pleiotropyb. epistasisc. random assortmentd. mutationAnswer: cSHORT ANSWER13. Topic:The process of evolution depends on genetic variation.Level: mediumClonal animals do not reshuffle their genes throughgenetic recombination, whereas sexually reproducing animals do.Explain how this difference could affect how pathogens interact with clonal animals and how they interactwith sexually reproducing animals.Answer:Since recombination creates new genotypes every generation, pathogens cannot become fully adapted to the genotypes of sexually reproducing animals.Because recombination does not occur in clonal animals, they gain new genetic variationonly through mutation, which is a very rare process. Thus pathogens can more easily adapt to the genetic variation in clonal animals.14. Topic:The process of evolution depends on genetic variation.Level: difficultDescribe the difference between synonymous and nonsynonymous mutation.Which type is morelikely to be affected by natural selection, and why?Answer:A synonymous mutat ion does not affect an organism’s phenotype, whereas a nonsynonymous mutation does affect phenotype.Natural selection acts on variation among phenotypes, and so natural selection will act only on nonsynonymous mutations, because they are the only mutations that affect an organism’s phenotype.15. Topic:The process of evolution depends on genetic variation.Level: difficultMany genetic diseases have severe or lethal effects in the homozygous form, yet alleles for these diseases arenot entirely removed by natural selection.Explain how dominance relationships among alleles allow deleterious mutations to remain in a population.Answer:When genetic diseases are caused by recessive alleles,they do harmtothe carrieronly in the homozygous form.The heterozygotes do not express the deleterious phenotype, and thus heterozygotes do not havereduced fitness. Deleterious genetic diseases thus can remain in the population because they are not selected against in the heterozygous form.Evolution can occur through random processes or through selection. MULTIPLE CHOICE16. Topic:Evolution can occur through random processes or through selection.Level: easyA process that occurs when genetic variation is lost because of random variation in mating, mortality, fecundity, and inheritance isknown asa. mutation.b. genetic drift.c. stabilizing selection.d. disruptive selection.Answer: b17. Topic:Evolution can occur through random processes or through selection.Level: mediumThe rate at which allele frequencies change because of genetic drift isa. highest in large populations.b. the same regardless of population size.c. highest in intermediate-sized populations.d. highest in small populations.Answer: d18. Topic:Evolution can occur through random processes or through selection.Level: mediumConsider three populations of a plant species, each isolated from other populations of the same species.Population X has contained approximately 100 individuals in each generation for the past 200 generations. Population Y has contained approximately 10,000 individuals in each generation for the past 200 generations.Population Z has contained approximately 1 million individuals in each generation for the past 200 generations.If genetic drift is the only evolutionary process acting on these populations, howcanwe expect the amount of genetic variation to differ among these populations?a. X will have thehighest variation, Y will have intermediate variation, and Z will have thelowest variation.b. X will have thelowest variation, Ywill have intermediate variation, and Zwill have thehighest variation.c. X and Z will have high variation, while Z will havelow variation.d. All three populations willhave the sameamount of genetic variation.Answer: b19. Topic:Evolution can occur through random processes or through selection.Level: mediumWhich is (are) correctabout founder effect?I.Founder effect occurs when individuals are transplanted to a new location.II. Founder effect producesnew alleles.III. Founder effect reduces genetic variation.a. Ionlyb. IIonlyc. IIIonlyd. I and IIe. I and IIIAnswer: e20. Topic:Evolution can occur through random processes or through selection.Level: mediumConsider a situation in which overharvesting causes the number of fish in a population to become drastically smaller, which causes genetic variation in that fish to decrease over a few generations. This is an example ofa. bottleneck effect.b. founder effect.c. directional selection.d. recombination.Answer: a21. Topic:Evolution can occur through random processes or through selection.Level: mediumThe four plots in the figureshow possible relationships between the survival and beak length in an island population of birds.Which plot is an example of disruptive selection?a. plot ab. plot bc. plot cd. plot dAnswer: c22. Topic:Evolution can occur through random processes or through selection.Level: mediumStickleback fish exhibit variation in a morphological trait known as gill rakers.Fish with long gill rakers are very good at eating plankton, and fish with short gill rakers are good at eating deep-water invertebrates.However, fish with intermediate-length gill rakers are poor at eating either type of food. Fish that are better at consuming food have higher survival and reproductionratesthan poorer consumers.Based on this information, what type of selection is likely acting on stickleback gill raker length?a. no natural selectionb. stabilizing selectionc. disruptive selectiond. directional selectionAnswer: c23. Topic:Evolution can occur through random processes or through selection.Level: difficultWhen a parental generationundergoesstabilizing selection, how willthe distribution of phenotypes in the population change between the parental generation and their progeny?a. Mean phenotype increases, but variability decreases.b. Mean phenotype stays the same, but variability decreases.c. Mean phenotype stays the same, but variability increases.d. Mean phenotype and variability both increase.Answer: b24. Topic:Evolution can occur through random processes or through selection.Level: easyWhen an extreme phenotype hashigher fitness than anaverage phenotype in a population, it is an example ofa. stabilizing selection.b. directional selection.c. disruptive selection.d. genetic drift.Answer: b25. Topic:Evolution can occur through random processes or through selection.Level: difficultIf a population of butterflies is under strong natural selection favoring large wings but there is no genetic variation for wing size, what dowe expect to occur in the next generation?a. Wings will evolve to be smaller.b. There will be no evolutionary change in wing size.c. Wings will evolve to be larger.d. Wings will evolve to be more variable.Answer: b26. Topic:Evolution can occur through random processes or through selection.Level: easyWhen a phenotype is under disruptive selection, which parts of the phenotypic distribution are expected to have the highest fitness?a. individuals with the extreme largest values of the phenotypeb. individuals with the extreme smallest values of the phenotypec. individuals with both extreme large and extreme small values of the phenotyped. individuals with the intermediate phenotypeAnswer: c27. Topic:Evolution can occur through random processes or through selection.Level: difficultConsider three populations of a plant species, each of which is isolated from other populations of the same species.Population X has hadapproximately 100 individuals in each generation for the past 200 generations. Population Y has hadapproximately 10,000 individuals in each generation for the past 200 generations.Population Z has hadapproximately 1 million individuals in each generation for the past 200 generations.If the environment changed and a new environmental condition exerted the exact same strength of directional selection on all three populations, which population would we expect to evolve most rapidly?a. Population Xb. Population Yc. Population Zd. All three populations would evolve at the same rate.Answer: cSHORT ANSWER28. Topic:Evolution can occur through random processes or through selection.Level: difficultYou conduct an experiment in which you raise sixreplicated lines of fruit flies for eightgenerations.You keep population size constant at 20 adults per generation.You are interested in a gene,bw,that affects eye color. This gene has two alleles,bw-1 and bw-2.You starteach replicated line with the frequency of the bw-1 allele at50%.Do thedata in the graph better match the prediction for the bw alleles evolving by genetic drift or by directional selection?Be sure to define directional selection and genetic drift and describe the prediction of both hypotheses.Answer:Thesedata better match the bw alleles evolving by genetic drift. Genetic drift is random changes in allele frequencies, while evolution by directional selection would consistently favor one allele over another. Withgenetic drift, we would predict some lines to show an increase inbw-1 allele frequency, some lines to decrease, and some to stay roughly the same.However, under directional selection, we would expect all six lines to consistently change in the same direction.For example, if bw-1werefavored by directional selection, we would expect bw-1 to increase in frequency in all six lines each generation.29. Topic:Evolution can occur through random processes or through selection.Level: mediumA small species of fly lays its eggs in plant stems.The developing fly larvae cause a gall, or large round structure, to form in the stem.Genetic differences among flies cause variation in the size of the galls they produce.Both birds and wasps feed on the larvae in the galls.The proportions of small, medium, and large galls able to survive attacks by either birds or wasps are shown in the table.If a population of flies lives in a field with equal abundance of birds and wasps, willgall size be bydirectional, stabilizing, or disruptive selection? Explain your answer.Answer: The galls would be under stabilizing selection, because the intermediate-sized galls are not attacked by either predator, but both large (25 mm) and small (15 mm) galls are attacked by predators.This meets the definition of stabilizing selection: that intermediate phenotypes have highest fitness, while the two extreme phenotypes have low fitness.30. Topic:analyzing ecology:strength of selection, heritability, and response to selectionLevel: mediumA group of island birds have beaks that are on average 20 mm long with a standard deviation of1 mm. Beak length is a geneticallybased trait with a heritability of 0.5. Only small seeds are available for these birds to consume, and some of the large-beaked birds are unable to reproduce.The group of birds that successfully reproduces has an average beak size of 16mm.Based on this information, predict how much the beak size is expected to change in the next generation.Answer:Use the equation R = h2S.h2 is the heritability 0.5. (Notethat we do not square the heritability.)S is the selection differential, (16 − 20) ÷1.We divide by 1for the standard deviation.R=0.5 ×−4 = −2.We thus predict the bird beak size will decrease by twostandard deviations in the next generation. Microevolution operates at the population level.MULTIPLE CHOICE31: Topic:Microevolution operates at the population level.Level: easyWhat is the term for evolution acting at the level of populations?a. microevolutionb. macroevolutionc. speciationd. key innovationsAnswer: a32. Topic:Microevolution operates at the population level.Level:easyThe human activity of controlling the survival and reproduction of organisms to produce offspring with specific sets of traits is known asa. artificial selection.b. natural selection.c. industrial melanism.d. speciation.Answer: a33. Topic:Microevolution operates at the population level.Level: easyThe drastic phenotypic differences between large dogs,such as bloodhounds, and small dogs,such as Chihuahuas,are a result ofa. genetic drift.b. founder effect.c. artificial selection.d. natural selection.Answer: c34. Topic:Microevolution operates at the population level.Level: mediumEvolution by artificial selection is similar to evolution by natural selection becauseI. both require traits to be heritable.II. both incorporate founder effects.III. both generate differences in fitness between individuals.a. I onlyb. II onlyc. III onlyd. I and III onlye. I, II, and IIIAnswer: d35. Topic:Microevolution operates at the population level.Level: mediumWhich is a prediction of the hypothesis that predation caused industrial melanism?a. Dark moths seek out dark trees to rest on.b. Birds more frequently capture dark moths on dark trees than those on light trees.cBirds more frequently capture dark moths on light treesthan those on dark trees.d. Industrial pollution led to higher mortality of light moths.Answer: c36. Topic:Microevolution operates at the population level.Level:easyThe phenomenon by which moths in England evolved from light-colored forms to dark-colored forms over several decades is known asa. speciation.b. epistasis.c. genetic drift.d. industrial melanism.Answer: d37. Topic:Microevolution operates at the population level.Level:easyWhich of the following insights about microevolution is demonstrated by industrial melanism?a. Artificial selection cannot be reversed.b. Microevolution is primarily caused by genetic drift.c. Humans affect the evolution only of domestic animals.d. Microevolution can occur in a very short time.Answer: d38. Topic:Microevolution operates at the population level.Level: mediumBody size is a heritable trait in the amphipod, an aquatic crustacean. Fish preferentially consume large amphipods, leaving primarily small amphipods to breed.Based on these observations, how would we expect evolution to affect ponds with and without fish?a. Ponds with fish should have larger amphipods.b. Ponds with fish should have smaller amphipods.c. Amphipod body size should not differ between ponds with and without fish.d. Ponds with fish should have amphipods that are either very large or very small.Answer: b.39. Topic:Microevolution operates at the population level.Level: mediumWhich of the following statements about evolution by artificial selection is correct?a. It occurs very slowly.b. It was discovered only in the 1900s.c. It can have negative effects on humans.d. It does not require genetic variation.Answer: c39. Topic:Microevolution operates at the population level.Level: easyThe evolution of pesticide resistance in insects is an example ofa.microevolution.b. industrial melanism.c. selective predation.d. macroevolution.Answer: a40. Topic:Microevolution operates at the population level.Level: easyMicroevolution includesa. speciation.b. key innovation.c. genetic drift.d. polyploidy.Answer: c41. Topic:Microevolution operates at the population level.Level: easyArtificial selection can cause evolutionary change when there isa. genetic variation in traits.b. geographic separation.c. a founder effect.d. key innovation.Answer: a42. Topic:Microevolution operates at the population level.Level: easyDarwin supported his argument for evolution by natural selection with the observation that artificial selection caused large changes in a short period becausea. natural selection had millions of years to operate.b. genetic drift could not cause the same rate of change.c. natural selection had to have occurred in only a few generations.d. allopatric speciation requires geographic barriers.Answer: aSHORT ANSWER43. Topic:Microevolution operates at the population level.Level: mediumIf climate change were to cause a tree with very dark bark to become common in England, what would we expect to happen to the color patterns of the peppered moth¸and why would we expect it to happen?Answer:Color pattern is genetically controlled in the peppered moth, and it also affects the survival of moths.Dark-colored moths resting on dark trees are less likely to be eaten by birds than dark moths on light trees.The opposite pattern is true for light-colored moths.Thus, if dark trees became common, the light moths would be more likely to be killed than the dark moths.In each generation the selective consumption of light moths would lead to an increase in the proportion of dark-colored genotypes in the moth population.Eventually the light-colored moths would be rare or absent.44. Topic:Microevolution operates at the population level.Level: mediumHow might understanding microevolutionhave a direct benefit to humans in the fight against diseases?Answer: A major danger to humans is the evolution of drug-resistant pathogens such as drug-resistant tuberculosis.Onereason drug-resistant pathogens evolve is inefficient application of drugs.Understanding the evolutionary processes that increase the rate of the evolution of drug resistance can help us develop strategies to limit or prevent it.45. Topic:Microevolution operates at the population level.Level:difficultThe drug chloroquine has been widely used to treat the human parasite malaria.Mutations in the malaria gene pfcrt confer resistance to chloroquine.In some countries, more than 90% of malaria parasites had the pfcrt resistance alleles.When these countries stopped using chloroquine, the frequency of the pfcrt resistance alleles rapidly declined.Provide an evolutionary explanation for the decline in pfcrt resistance alleles after chloroquine was discontinued.Answer:Although the pfcrt resistance alleles had the highest fitness when chloroquine was used, it is likely that the pfcrt resistance alleles had lower fitness than other alleles in the absence of chloroquine.Thus, in the absence of chloroquine, natural selection removed the pfcrt resistance alleles from the population.Macroevolution operates at the species level and higher levels of taxonomic organization.MULTIPLE CHOICEUse the following figure to answer questions 46 and 47.46. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: easyBased on the phylogeny in the figure, which traits are shared by bony fishes and amphibians?a. jaws and lungsb. bony skeleton and lungsc. jaws and bony skeletond. legs and lungsAnswer: c47.Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumBased on the phylogeny in the figure, which group is most closely related to the reptiles?a. lampreysb. lungfishesc. amphibiansd. mammalsAnswer: dorganization.Level: easyWhat is the term for evolution that acts at the level of species, genera, and higher levels of organization?a. microevolutionb. macroevolutionc. genetic driftd. epistasisAnswer: b49. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: easyWhich of the following is a component of macroevolution?a. artificial selectionb. epistasisc. founder effectd. sympatric speciationAnswer: d50. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumWhich of the following three statements is (are) correct?I. Speciation through polyploidy can occur through hybridization.II. Speciation through polyploidy never occurs in vertebrates; it occursonly in plants.III. Speciation through polyploidy generates phenotypic differences among the resulting species.a. I onlyb. IIonlyc. IIIonlyd. I and IIe. I and IIIAnswer: e51. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: easyWhich of the following is a necessary component of allopatric speciation?a. hybridizationb. polyploidyc. a geographic barrierd. key innovationsAnswer: corganization.Level: easyAn evolutionary novel trait that allows a species to use new niches and undergo a high rate of speciation isa. a key innovation.b. a polyploid species.c. pleiotropy.d. a phylogenetic tree.Answer: a53. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumAngiosperms, the flowering plants, are much more diverse than other groups of plants.One reason for this is the evolution of flowers, which increased plant interactions with pollinators and drastically increased speciation rates.This is an example ofa. microevolution.b. key innovation.c. pleiotropy.d. disruptive selection.Answer:b54. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: easyWhen an error in meiosis causes sexually reproducing species to generate zygotes with three or more sets of chromosomes, this is known asa. pleiotropy.b. epistasis.c. polyploidy.d. genetic drift.Answer: c55. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumWhich of the following is (are) correct?I. Allopatric speciation can occur without geographic barriers.II. Allopatric speciation is the most common form of speciation.III. Allopatric speciation can be facilitated through genetic drift.a. I onlyb. II onlyc. III onlyd. I and IIIe. II and IIIAnswer: e56. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumWhich of the following is(are) correct?I. Sympatric speciation occurs without geographic barriers.II. Sympatric speciation can occur through polyploidy.III. Sympatric speciation is less common than allopatric speciation.a. I onlyb. II onlyc. III onlyd. I and IIIe. I, II, and IIIAnswer: e57. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumBased on the phylogeny of the Galapagos finches, which statement is correct?a. Eating insects is a key innovation.b. The ancestor of the small tree finch and large tree finch probably ate insects.c. The ancestor of the large cactus finch and common cactus finch likely ate insects.d. The small tree finch is most closely related to the sharp-beaked finch.Answer: bSHORT ANSWER58. Topic:Macroevolution operates at the species level and higher levels of taxonomic organization.Level: mediumDescribe how genetic drift and natural selection can play a role in allopatric speciation. Answer:After an original population has been split into two populations by a geographic barrier, genetic drift and natural selection can change the allele frequencies and the resulting phenotypes such that the two populations are no longer capable of breeding with one another.This can occur through genetic drift if the populations are small enough to allow large changes in allele frequencies in each population.It can occur through natural selection if different alleles are favored by different environments on either side of the geographic barrier.。