This Document Contains Chapters 21 to 22 Chapter 21: The Evolution of Populations 21.1 Multiple-Choice Questions 1) If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be A) 23%. B) 46%. C) 54%. D) There is not enough information to say. Answer: C 2) Which variable is likely to undergo the largest change in value resulting from a mutation that introduces a new allele into a population at a locus for which all individuals formerly had been fully homozygous? A) average heterozygosity B) nucleotide variability C) geographic variability D) average number of loci Answer: A 3) Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? A) Each bird evolved a deeper, stronger beak as the drought persisted. B) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted. C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. D) The frequency of the strong-beak alleles increased in each bird as the drought persisted. Answer: B 4) The higher the proportion of loci that are "fixed" in a population, the lower is that population's A) nucleotide variability only. B) chromosome number only. C) average heterozygosity only. D) nucleotide variability, average heterozygosity, and chromosome number. E) nucleotide variability and average heterozygosity. Answer: E 5) Rank the following one-base-point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide: 1. insertion mutation deep within an intron 2. substitution mutation at the third position of an exonic codon 3. substitution mutation at the second position of an exonic codon 4. deletion mutation within the first exon of the gene A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 2, 1, 4, 3 D) 3, 1, 4, 2 E) 2, 3, 1, 4 Answer: B 6) Which of the following is a true statement concerning genetic variation? A) It is created by the direct action of natural selection. B) It arises in response to changes in the environment. C) It must be present in a population before natural selection can act upon the population. D) It tends to be reduced by the processes involved when diploid organisms produce gametes. E) A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity. Answer: C 7) How many of these statements regarding populations are true? 1. Mature males and females of a population can interbreed with each other. 2. Populations are sometimes geographically isolated from other populations. 3. Biological species are made up of populations. 4. Members of a population tend to be genetically more similar to each other than to members of other populations. 5. Populations have genomes, but not gene pools. A) Only one of these statements is true. B) Two of these statements are true. C) Three of these statements are true. D) Four of these statements are true. E) All five of these statements are true. Answer: D 8) Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus A) the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change. B) natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency. C) this means that, at this locus, two alleles are present in equal proportions. D) the population itself is not evolving, but individuals within the population may be evolving. Answer: A 9) In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because A) the population is diploid. B) heterozygotes can come about in two ways. C) the population is doubling in number. D) heterozygotes have two alleles. Answer: B 10) In the formula for determining a population’s genotype frequencies, the pq in the term 2pq is necessary because A) the population is diploid. B) heterozygotes can come about in two ways. C) the population is doubling in number. D) heterozygotes have two alleles. Answer: D 11) Hardy-Weinberg equilibrium must occur in populations where A) an allele remains fixed. B) no genetic variation exists. C) natural selection is not operating. D) All three of the responses above are correct. E) Only two of the responses above are correct. Answer: E 12) In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele? A) 0.09 B) 0.49 C) 0.9 D) 9.0 E) 49.0 Answer: A 13) In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals that are heterozygous for this allele? A) 0.002 B) 0.020 C) 0.04 D) 0.16 E) 0.32 Answer: E 14) In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype? A) 0.20 B) 0.32 C) 0.42 D) 0.81 E) Genotype frequency cannot be determined from the information provided. Answer: D 15) You sample a population of butterflies and find that 56% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population? A) 0.07 B) 0.08 C) 0.09 D) 0.70 E) Allele frequency cannot be determined from this information. Answer: E 16) In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population? A) 0.36 B) 0.64 C) 0.75 D) 0.80 Answer: D 17) Which statement about variation is true? A) All phenotypic variation is the result of genotypic variation. B) All genetic variation produces phenotypic variation. C) All nucleotide variability results in neutral variation. D) All new alleles are the result of nucleotide variability. E) All geographic variation results from the existence of clines. Answer: D 18) Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence? A) mutation B) nonrandom mating C) genetic drift D) natural selection E) gene flow Answer: C 19) Evolution A) must happen, due to organisms' innate desire to survive. B) must happen whenever a population is not well adapted to its environment. C) can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met. D) requires the operation of natural selection. E) requires that populations become better suited to their environments. Answer: C 20) Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing A) nonrandom mating. B) geographic isolation. C) genetic drift. D) gene flow. Answer: D 21) If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of A) genetic drift. B) the bottleneck effect. C) the founder effect. D) genetic drift and the founder effect. E) all three of these. Answer: D 22) Which of the following statements best summarizes evolution as it is viewed today? A) It represents the result of selection for acquired characteristics. B) It is synonymous with the process of gene flow. C) It is the descent of humans from the present-day great apes. D) It is the differential survival and reproduction of the most-fit phenotypes. Answer: D 23) What is true of natural selection? A) Natural selection is a random process. B) Natural selection creates beneficial mutations. C) The only way to eliminate harmful mutations is through natural selection. D) Mutations occur at random; natural selection can preserve and distribute beneficial mutations. E) Mutations occur when directed by the good of the species; natural selection edits out harmful mutations and causes populations to adapt to the beneficial mutations. Answer: D 24) The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophage at any point in time results from A) frequency-dependent selection. B) evolutionary imbalance. C) heterozygote advantage. D) neutral variation. E) genetic variation being preserved by diploidy. Answer: A 25) The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. Over the course of evolutionary time, what should occur? A) Methylated DNA should become fixed in the gene pools of bacterial species. B) Nonmethylated DNA should become fixed in the gene pools of bacteriophages. C) Methylated DNA should become fixed in the gene pools of bacteriophages. D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time. E) Both the first and second responses are correct. Answer: D 26) Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive): 1. natural selection 2. microevolution 3. intrasexual selection 4. evolution 5. sexual selection A) 4, 1, 2, 3, 5 B) 4, 2, 1, 3, 5 C) 4, 2, 1, 5, 3 D) 1, 4, 2, 5, 3 E) 1, 2, 4, 5, 3 Answer: C 27) Sexual dimorphism is most often a result of A) pansexual selection. B) stabilizing selection. C) intrasexual selection. D) intersexual selection. E) artificial selection. Answer: D 28) In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birds' diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the male's feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal). During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? A) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. B) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. C) There should be directional selection for bright red feathers in males. D) Three of the statements are correct. E) Two of the statements are correct. Answer: D 29) During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following terms are appropriately applied to this situation? A) sexual selection B) mate choice C) intersexual selection D) Three of the responses are correct. E) Two of the responses are correct. Answer: D 30) Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then A) sexual dimorphism was developing over time in these species. B) intrasexual selection seems to have occurred. C) stabilizing selection was occurring in these species concerning larynx size. D) selection was acting more directly upon genotype than upon phenotype. Answer: A 31) Which of the following is most likely to produce an African butterfly species in the wild whose members have one of two strikingly different color patterns? A) artificial selection B) directional selection C) stabilizing selection D) disruptive selection E) sexual selection Answer: D 32) Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. Which of the following terms best describes this situation? A) artificial selection B) directional selection C) stabilizing selection D) disruptive selection E) sexual selection Answer: C 33) The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool? A) heterozygote advantage B) stabilizing selection C) diploidy D) balancing selection Answer: C 34) Heterozygote advantage should be most closely linked to which of the following? A) sexual selection B) stabilizing selection C) random selection D) directional selection E) disruptive selection Answer: B 35) In seed cracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population? A) disruptive selection B) directional selection C) stabilizing selection D) No selection would operate because the population is in Hardy-Weinberg equilibrium. Answer: B 36) When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of A) sexual selection. B) disruptive selection. C) balancing selection. D) stabilizing selection. E) frequency-dependent selection. Answer: E 37) The same gene that causes various coat patterns in wild and domesticated cats also causes a cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations? A) Evolution is progressive and tends toward a more perfect population. B) Phenotype is often the result of compromise. C) Natural selection reduces the frequency of maladaptive genes in populations over the course of time. D) Polygenic inheritance is generally maladaptive, and should become less common in future generations. E) In all environments, coat pattern is a more important survival factor than is eye-muscle tone. Answer: B 38) A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do not seem to be optimally arranged because A) natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time. B) in many cases, phenotype is not merely determined by genotype, but by the environment as well. C) though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design. D) natural selection is generally limited to modifying structures that were present in previous generations and in previous species. Answer: D 39) There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception? A) Advantageous alleles do not arise on demand. B) A population's evolution is limited by historical constraints. C) Adaptations are often compromises. D) Evolution can be influenced by environmental change. Answer: A 21.2 Art Questions 1) Blue light is a portion of the visible spectrum that penetrates deep into bodies of water. Ultraviolet (UV) light, though, can penetrate even deeper. A gene within a population of marine fish that inhabits depths from 500 m to 1,000 m has an allele for a photopigment that is sensitive to UV light, and another allele for a photopigment that is sensitive to blue light. Which of the graphs in Figure 21.1 best depicts the predicted distribution of these alleles within a population if the fish that carry these alleles prefer to locate themselves where they can see best? Figure 21.1 A) A B) B C) C D) D Answer: B 2) Anopheles mosquitoes, which carry the malaria parasite, cannot live above elevations of 5,900 feet. In addition, oxygen availability decreases with higher altitude. Consider a hypothetical human population that is adapted to life on the slopes of Mt. Kilimanjaro in Tanzania, a country in equatorial Africa. Mt. Kilimanjaro's base is about 2,600 feet above sea level and its peak is 19,341 feet above sea level. If the incidence of the sickle-cell allele in the population is plotted against altitude (feet above sea level), which of the following distributions is most likely, assuming little migration of people up or down the mountain? A) B) C) D) Answer: B Use Figure 21.2 to answer the following question. Figure 21.2 3) Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by A) genetic bottleneck. B) sexual selection. C) habitat differentiation. D) founder effect. Answer: D In a very large population, a quantitative trait has the distribution pattern shown in Figure 21.3. Figure 21.3 4) If the curve in Figure 21.3 shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations. Which of the following is (are) probably occurring? 1. immigration or emigration 2. directional selection 3. adaptation 4. genetic drift 5. disruptive selection A) 1 only B) 4 only C) 2 and 3 D) 4 and 5 E) 1, 2, and 3 Answer: C 5) If global warming permits mosquitoes to live at higher altitudes than they currently do, then in which direction should the entire plot in the correct distribution below be shifted? a. b. c. d. A) Curve A will be shifted to the right. B) Curve B will be shifted to the right. C) Curve C will be shifted upward. D) Curve D will be shifted upward. Answer: B 21.3 Scenario Questions The following questions refer to the information in the following paragraph. HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. 1) Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)? A) using a series of NAs, one at a time, and changed about once a week B) using a single PI, but slowly increasing the dosage over the course of a week C) using high doses of NA and a PI at the same time for a period not to exceed one day D) using moderate doses of NA and two different PIs at the same time for several months Answer: D 2) Every HIV particle contains two RNA molecules. If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true? A) There are now fewer genes within the viral particle. B) There are now more genes within the viral particle. C) A point substitution mutation has occurred in the retroviral genome. D) The retroviral equivalent of crossing over has occurred, no doubt resulting in a heightened positive effect. E) One of the RNA molecules has experienced gene duplication as the result of translocation. Answer: E 3) In a hypothetical population's gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations? A) The proportions of both types of homozygote should decrease. B) The proportion of the population that is heterozygous at this locus should remain constant. C) The population's average heterozygosity should decrease. D) The two homozygotes should decrease at different rates. Answer: B Use this information to answer the following questions. A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. 4) What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time? A) The population is undergoing genetic drift. B) The two phenotypes are about equally adaptive under laboratory conditions. C) The genotype AA is lethal. D) There has been a high rate of mutation of allele A to allele a. E) There has been sexual selection favoring allele a. Answer: B 5) What is the estimated frequency of allele A in the gene pool? A) 0.25 B) 0.50 C) 0.75 D) 0.125 Answer: B 6) What proportion of the population is probably heterozygous (Aa) for this trait? A) 0.05 B) 0.25 C) 0.50 D) 0.75 Answer: C Use this information to answer the following questions. You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown. 7) In which population would it be least likely that an accident would significantly alter the frequency of the brown allele? A) population A B) population B C) population C D) They are all the same. E) It is impossible to tell from the information given. Answer: B 8) Which population is most likely to be subject to the bottleneck effect? A) population A B) population B C) population C D) They are all equally likely. E) It is impossible to tell from the information given. Answer: A Use the following information to answer the following questions. In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. 9) With respect to the sickle-cell allele, what should be true of the β hemoglobin locus in U.S. populations of African-Americans whose ancestors were from equatorial Africa? 1. The average heterozygosity at this locus should be decreasing over time. 2. There is an increasing heterozygote advantage at this locus. 3. Diploidy is helping to preserve the sickle-cell allele at this locus. 4. Frequency-dependent selection is helping to preserve the sickle-cell allele at this locus. A) 1 only B) 1 and 3 C) 2 and 3 D) 1, 2, and 3 E) 1, 2, and 4 Answer: B 10) Although selection is clearly present, if the ideal equilibrium of alleles existed, what should be the proportion of heterozygous individuals in populations that live here? A) 0.04 B) 0.16 C) 0.20 D) 0.32 E) 0.80 Answer: D 11) Again, if this population were in equilibrium and if the sickle-cell allele is recessive, what proportion of the population should be susceptible to sickle-cell anemia under typical conditions? A) 0.04 B) 0.16 C) 0.20 D) 0.32 E) 0.80 Answer: A 12) Considering the overall human population of the U.S. mainland at the time when the slave trade brought large numbers of people from equatorial Africa, what was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population? A) natural selection B) gene flow C) genetic drift D) founder effect E) Two of the responses are correct. Answer: B 13) The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles such as this can help explain why A) new advantageous alleles do not arise on demand. B) evolution is limited by historical constraints. C) adaptations are often compromises. D) chance events can affect the evolutionary history of populations. Answer: C 14) In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa? A) stabilizing selection; disruptive selection B) disruptive selection; stabilizing selection C) disruptive selection; directional selection D) directional selection; disruptive selection E) directional selection; stabilizing selection Answer: E In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes. 15) Which of these is closest to the allele frequency in the founding population? A) 0.1 a, 0.9 A B) 0.2 a, 0.8 A C) 0.5 a, 0.5 A D) 0.8 a, 0.2 A E) 0.4 a, 0.6 A Answer: A 16) If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planet's population reaches 10,000? A) 100 B) 400 C) 800 D) 1,000 E) 10,000 Answer: A 17) If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of A) diploidy. B) gene flow. C) genetic drift. D) disruptive selection. E) stabilizing selection. Answer: C 18) You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to A) cross your flies with flies from another lab. B) reduce the number of flies that you transfer at each generation. C) transfer only the largest flies. D) change the temperature at which you rear the flies. E) shock the flies with a brief treatment of heat or cold to make them more hardy. Answer: A 19) Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur? A) The new virus will maintain its Tamiflu-resistance gene, just in case of future exposure to Tamiflu. B) The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. C) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. D) If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will become dormant until Tamiflu is present. Answer: C 21.4 End-of-Chapter Questions 1) Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others. A) alleles B) loci C) gene pools D) species E) individuals Answer: E 2) No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is A) new mutations that occurred in the preceding generation. B) genetic drift due to the small size of the population. C) the reshuffling of alleles in sexual reproduction. D) natural selection. E) environmental effects. Answer: C 3) Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating A) the bottleneck effect. B) disruptive selection. C) frequency-dependent selection. D) neutral variation. E) stabilizing selection. Answer: E 4) If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus? A) gene variability = 0%; number of alleles = 0 B) gene variability = 0%; number of alleles = 1 C) gene variability = 0%; number of alleles = 2 D) gene variability > 0%; number of alleles = 2 E) Without more information, gene variability and number of alleles cannot be determined. Answer: B 5) There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from A) genetic drift. B) gene flow. C) disruptive selection. D) nonrandom mating. E) directional selection. Answer: A 6) A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? A) 0.7 B) 0.49 C) 0.21 D) 0.42 E) 0.09 Answer: D Chapter 22: The Origin of Species 22.1 Multiple-Choice Questions 1) What is true of macroevolution? A) It is the same as microevolution, but includes the origin of new species. B) It is evolution above the species level. C) It is defined as the evolution of microscopic organisms into organisms that can be seen with the naked eye. D) It is defined as a change in allele or gene frequency over the course of many generations. E) It is the conceptual link between irritability and adaptation. Answer: B 2) What is true of the flightless cormorants of the Galápagos Islands? A) They are descendants of the same common ancestor that gave rise to the unique finches of these islands. B) They are close relatives of flightless cormorants from the Americas. C) If they are still able to breed successfully with flying cormorants, it would probably be with North American cormorants, rather than with South American cormorants. D) Flightless cormorants on one island have restricted gene flow with those on other islands, which could someday lead to a macroevolutionary event. E) Their DNA has low levels of sequence homology with the DNA of flying American cormorants. Answer: D 3) Which of the following statements about species, as defined by the biological species concept, is (are) correct? I. Biological species are defined by reproductive isolation. II. Biological species are the models used for grouping extinct forms of life. III. The biological species is the largest unit of population in which successful interbreeding is possible. A) I and II B) I and III C) II and III D) I, II, and III Answer: B 4) Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools? A) phylogenetic B) ecological C) biological D) morphological Answer: C 5) There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans or into a separate species of their own. Most DNA sequence data analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept is most applicable in this example? A) phylogenetic B) ecological C) morphological D) biological Answer: D 6) You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use? A) biological B) phylogenetic C) ecological D) morphological Answer: D 7) Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms? A) reduced hybrid fertility B) hybrid breakdown C) mechanical isolation D) habitat isolation E) gametic isolation Answer: D 8) Rank the following from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. sperm–egg incompatibility in sea urchins 4. prezygotic isolating mechanism A) 2, 3, 1, 4 B) 2, 4, 1, 3 C) 4, 1, 2, 3 D) 4, 2, 1, 3 E) 2, 1, 4, 3 Answer: B 9) Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two frog species separate? A) the postzygotic barrier called hybrid in viability B) the postzygotic barrier called hybrid breakdown C) the prezygotic barrier called hybrid sterility D) gametic isolation Answer: A 10) Theoretically, the production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) should A) result in the extinction of one of the two parental species. B) cause convergent evolution. C) strengthen postzygotic barriers between horses and donkeys. D) weaken the intrinsic reproductive barriers between horses and donkeys. E) eventually result in the formation of a single species from the two parental species. Answer: C 11) Dogs (Canis lupus familiaris) and gray wolves (Canis lupus) can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time) and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species? A) ecological and morphological B) ecological and phylogenetic C) morphological and phylogenetic D) biological and morphological E) biological and phylogenetic Answer: E 12) What does the biological species concept use as the primary criterion for determining species boundaries? A) geographic isolation B) niche differences C) gene flow D) morphological similarity E) molecular (DNA, RNA, protein) similarity Answer: C 13) Which of the following statements about speciation is correct? A) The goal of natural selection is speciation. B) When reunited, two allopatric populations will interbreed freely if speciation has occurred. C) Natural selection chooses the reproductive barriers for populations. D) It always takes millions of years for speciation to occur. E) Speciation is a basis for understanding macroevolution. Answer: E 14) Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species, then which of these terms are applicable? 1. sympatric species 2. prezygotic isolation 3. postzygotic isolation 4. allopatric species 5. habitat isolation 6. reduced hybrid fertility A) 1 and 2 B) 2 and 4 C) 1, 3, and 6 D) 2, 4, and 5 E) 1, 2, 5, and 6 Answer: A 15) In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In rangelands of the western United States, pronghorns and cattle often associate with one another. If some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood, then over time which of these should occur, if the host mammal can be considered as the fleas' habitat? 1. reproductive isolation 2. sympatric speciation 3. habitat isolation 4. prezygotic barriers A) 1 only B) 2 and 3 C) 1, 2, and 3 D) 2, 3, and 4 E) 1 through 4 Answer: E 16) The difference between geographic isolation and habitat differentiation is the A) relative locations of two populations as speciation occurs. B) speed (tempo) at which two populations undergo speciation. C) amount of genetic variation that occurs among two gene pools as speciation occurs. D) identity of the phylogenetic kingdom or domain in which these phenomena occur. E) the ploidy of the two populations as speciation occurs. Answer: A 17) Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species? 1. allopatric speciation 2. sympatric speciation 3. sexual selection 4. polyploidy A) 1 and 3 B) 1 and 4 C) 2 and 3 D) 2 and 4 Answer: D 18) Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it? A) allopatric speciation; ecological isolation B) sympatric speciation; habitat differentiation C) allopatric speciation; behavioral isolation D) sympatric speciation; sexual selection E) sympatric speciation; allopolyploidy Answer: B 19) The origin of a new plant species by hybridization, coupled with accidents during cell division, is an example of A) allopatric speciation. B) sympatric speciation. C) autopolyploidy. D) habitat selection. Answer: B 20) The most likely explanation for the high rate of sympatric speciation that apparently existed among the cichlids of Lake Victoria in the past is A) sexual selection. B) habitat differentiation. C) polyploidy. D) pollution. E) introduction of a new predator. Answer: A 21) The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and A) their chromosomes are no longer homologous enough to permit meiosis. B) a constant number of viable, fertile hybrids is produced over the course of generations. C) the hybrid zone is inhospitable to hybrid survival. D) an increasing number of viable, fertile hybrids is produced over the course of generations. E) a decreasing number of viable, fertile hybrids is produced over the course of generations. Answer: D 22) A hybrid zone is properly defined as A) an area where two closely related species' ranges overlap. B) an area where mating occurs between members of two closely related species, producing viable offspring. C) a zone that features a gradual change in species composition where two neighboring ecosystems border each other. D) a zone that includes the intermediate portion of a cline. E) an area where members of two closely related species intermingle, but experience no gene flow. Answer: B 23) Which of these should decline in hybrid zones where reinforcement is occurring? A) gene flow between distinct gene pools B) speciation C) the genetic distinctness of two gene pools D) mutation rate E) hybrid sterility Answer: A 24) The most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is A) reinforcement. B) fusion. C) stability. D) geographic isolation. E) polyploidy. Answer: B 25) A narrow hybrid zone separates the toad species Bombina and Bombina variegata. What is true of those alleles that are unique to the parental species? A) Such alleles should be absent. B) Their allele frequency should be nearly the same as the allele frequencies in toad populations distant from the hybrid zone. C) The alleles' heterozygosity should be higher among the hybrid toads there. D) Their allele frequency on one edge of the hybrid zone should roughly equal their frequency on the opposite edge of the hybrid zone. Answer: C 26) According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that A) the species is now extinct. B) speciation occurred instantaneously. C) speciation occurred in one generation. D) speciation occurred rapidly in geologic time. E) the species will consequently have a relatively short existence, compared with other species. Answer: D 27) According to the concept of punctuated equilibrium, A) natural selection is unimportant as a mechanism of evolution. B) given enough time, most existing species will gradually give rise to new species. C) a new species accumulates most of its unique features as it comes into existence. D) evolution of new species features long periods during which changes are occurring, interspersed with short periods of equilibrium, or stasis. E) transitional fossils, intermediate between newer species and their parent species, should be abundant. Answer: C 28) Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species, then which of these terms is applicable? A) behavioral isolation B) mechanical isolation C) hybrid breakdown D) reduced hybrid viability Answer: B 29) Speciation A) occurs at such a slow pace that no one has ever observed the emergence of new species. B) occurs only by the accumulation of genetic change over vast expanses of time. C) must begin with the geographic isolation of a small, frontier population. D) and macroevolution are synonymous. E) can involve changes to a single gene. Answer: E 30) In order for speciation to occur, what must be true? A) The number of chromosomes in the gene pool must change. B) Changes to centromere location or chromosome size must occur within the gene pool. C) Large numbers of genes that affect a single phenotypic trait must change. D) Large numbers of genes that affect numerous phenotypic traits must change. E) At least one gene, affecting at least one phenotypic trait, must change. Answer: E 22.2 Art Questions The next few questions refer to the following description. In the ocean, on either side of the Isthmus of Panama, are 30 species of snapping shrimp; some are shallow-water species, and others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. In Figure 22.1, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1–5), with 1 being the shallowest. Figure 22.1 1) In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4? A) A3 B) A5 C) B4 D) either A3 or A5 E) any species from any one of the side A habitats Answer: C 2) Which of these habitats is likely to harbor the youngest species? A) A5 B) B4 C) A3 D) B2 E) A1 Answer: E 3) Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other? A) A1 and A5 B) A1 and B5 C) B5 and B1 D) A5 and B5 E) Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence. Answer: D 4) Which factor is most important for explaining why there are equal numbers of snapping shrimp species on either side of the isthmus? A) the relative shortness of time they have been separated B) the depth of the ocean C) the number of actual depth habitats between the surface and the sea floor D) the elevation of the isthmus above sea level E) the depth of the canal Answer: A 5) There are currently two large, permanent bridges that span the Panama Canal. The bridges are about 8 miles apart. If snapping shrimp avoid swimming at night and avoid swimming under shadows, then what do these bridges represent for the snapping shrimp? A) sources of refuge B) geographic barriers C) sources of a hybrid zone between the two bridges D) sources for increased gene flow Answer: B 6) The Panama Canal was completed in 1914, and its depth is about 50 feet. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal? A) A5 and B5 B) A3 and B3 C) A1 and B1 D) either A1 and A2, or B1 and B2 E) A1–A3 and B1–B3 have equal likelihoods of harboring snapping shrimp species that can hybridize. Answer: C In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits migration to occur between populations of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and 10 years after the bridge's completion, researchers collected 10 antelope squirrels from both sides of the river, took blood samples, and collected frequencies of alleles unique to the two types of antelope squirrels (see the graphs in Figures 22.2 and 22.3). Figure 22.2 Figure 22.3 7) The data in these graphs indicate that A) a hybrid zone was established after the completion of the bridge. B) there was no migration between the two squirrel populations after the bridge was completed. C) gene flow occurred from one type of squirrel into the gene pool of the other type of squirrel. D) two-way migration of squirrels occurred across the bridge, but without hybridization. E) some northern squirrels migrated south, but no southern squirrels migrated north across the bridge. Answer: D The next few questions refer to the evolutionary tree in Figure 22.4, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change. Figure 22.4 8) Which species is most closely related to species W? A) V is most closely related to species W. B) X is most closely related to species W. C) Y and Z are equally closely related to W. D) It is not possible to say from this tree. Answer: A 9) Which species is least expected to have a good record of transitional fossils; in other words, which species' fossils, if present at all, are expected only in relatively superficial (i.e., shallow) strata? A) V B) W C) X D) Y E) Z Answer: A 10) Which of these five species originated earliest and appeared suddenly in the fossil record? A) V B) W C) X D) Y E) Z Answer: B 11) Which conclusion can be drawn from this evolutionary tree? A) Gradualistic speciation and speciation involving punctuated equilibrium are mutually exclusive concepts; only one of them can occur. B) Eldredge and Gould would deny that the lineages labeled X, Y, and Z could represent true species. C) Assuming that the tip of each line represents a species, there are five extant (i.e., not extinct) species resulting from the earliest common ancestor. D) A single clade (i.e., a group of species that share a common ancestor) can exhibit both gradualism and punctuated equilibrium. E) V and W shared a common ancestor more recently than any of the other species. Answer: D 12) Which of these five species is the extant (i.e., not extinct) species that is most closely related to species X, and why is this so? A) V; shared a common ancestor with X most recently B) W; shared a common ancestor with X most recently C) Y; arose in the same fashion (i.e., at the same tempo) as X D) Z; shared a common ancestor with X most recently, and arose in the same fashion as X E) This tree does not provide enough information to answer this question. Answer: A 22.3 Scenario Questions The next few questions refer to the following description. On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island's lowlands, and is also found on the African mainland, located about 200 miles away. At higher elevations, and only on Sao Tomé, is found the very closely related Drosophila santomea. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly outnumbered by D. santomea. Studies of the two species' nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago. 1) Which of the following reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids? A) hybrid breakdown B) hybrid in viability C) hybrid sterility D) temporal isolation E) a geographic barrier Answer: C 2) If a speciation event occurred on Sao Tomé, producing D. santomea from a parent colony of D. yakuba, then which of the following terms applies (apply)? I. macroevolution II allopatric speciation III. sympatric speciation A) I only B) II only C) I and II D) I and III Answer: D 3) Using only the information provided in the paragraph, which of the following is the best initial hypothesis for how D. santomea descended from D. yakuba? A) geographic isolation B) autopolyploidy C) habitat differentiation D) sexual selection E) allopolyploidy Answer: C 4) The observation that island D. yakuba are more closely related to mainland D. yakuba than island D. yakuba are to D. santomea is best explained by proposing that D. santomea A) descended from a now-extinct, non-African fruit fly. B) arrived on the island before D. yakuba. C) descended from a single colony of D. yakuba, which had been introduced from elsewhere, with no subsequent colonization events. D) descended from an original colony of D. yakuba, of which there are no surviving members. The current island D. yakuba represent a second colonization event from elsewhere. Answer: D 5) Which of these evolutionary trees represents the situation described in the previous paragraph? (Note: Yakuba (I) represents the island population, and yakuba (M) represents the mainland population.) A) B) C) D) Answer: A 6) If the low number of hybrid flies in the hybrid zone, relative to the number of D. santomea flies there, is due to the fact that hybrids are poorly adapted to conditions in the hybrid zone, and if fewer hybrid flies are produced with the passage of time, these conditions will most likely lead to A) fusion. B) reinforcement. C) stability. D) further speciation events. Answer: B The next few questions refer to the following description. On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated, freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time. When placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences. 7) Which type of reproductive isolation operates to keep the mosquitofish isolated, even when fish from different ponds are reunited in the same body of water? A) behavioral isolation B) habitat isolation C) temporal isolation D) mechanical isolation E) gametic isolation Answer: A 8) Which two of the following have operated to increase divergence between mosquitofish populations on Andros? 1. improved gene flow 2. bottleneck effect 3. sexual selection 4. founder effect 5. natural selection A) 1 and 3 B) 2 and 3 C) 2 and 4 D) 3 and 4 E) 3 and 5 Answer: E 9) What is the best way to promote fusion between two related populations of mosquitofish, one of which lives in a predator-rich pond, and the other of which lives in a predator-poor pond? A) Build a canal linking the two ponds that permits free movement of mosquitofish, but not of predators. B) Transfer only female mosquitofish from a predator-rich pond to a predator-poor pond. C) Perform a reciprocal transfer of females between predator-rich and predator-poor ponds. D) Remove predators from a predator-rich pond and transfer them to a predator-poor pond. Answer: A 10) If one builds a canal linking a predator-rich pond to a predator-poor pond, then what type(s) of selection should subsequently be most expected among the mosquitofish in the original predator-rich pond, and what type(s) should be most expected among the mosquitofish in the formerly predator-poor pond? A) stabilizing selection; directional selection B) stabilizing selection; stabilizing selection C) less-intense directional selection; more-intense directional selection D) less-intense disruptive selection; more-intense disruptive selection Answer: C 11) The predatory fish rely on visual cues and speed to capture mosquitofish. Mosquitofish rely on speed and visual cues to avoid the predatory fish. Which adaptation(s) might help the predators survive in ponds that are home to faster mosquitofish? 1. directional selection for increased speed 2. stabilizing selection for speed that matches that of the mosquitofish 3. change in hunting behavior that replaces reliance on visual cues with reliance on tactile cues, which can be used to hunt at night 4. change in hunting behavior that eliminates speed in favor of better camouflage, which permits an ambush strategy A) 1 only B) 2 only C) either 1 or 3 D) either 2 or 3 E) 1, 3, or 4 Answer: E The next question refers to the following description. In the ocean, on either side of the Isthmus of Panama, are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago. 12) Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp? A) They have been geographically isolated from each other for a longer time. B) Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting in faster divergence in deepwater shrimp. C) The rise of the land bridge was accompanied by much volcanic activity. Volcanic ash contains heavy metals, which are known mutagens. Ash fall caused high levels of heavy metals in the ocean sediments underlying the deep water, resulting in accelerated mutation rates and faster divergence in deepwater shrimp. D) Fresh water entering the ocean from the canal is both less dense and cloudier than seawater. The cloudy fresh water interferes with the ability of shallow-water shrimp to locate mating partners, which reduces the frequency of mating, thereby slowing the introduction of genetic variation. Answer: A 22.4 End-of-Chapter Questions 1) The largest unit within which gene flow can readily occur is a A) population. B) species. C) genus. D) hybrid. E) phylum. Answer: B 2) Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent? A) habitat isolation B) temporal isolation C) behavioral isolation D) gametic isolation E) postzygotic barriers Answer: C 3) According to the punctuated equilibria model, A) natural selection is unimportant as a mechanism of evolution. B) given enough time, most existing species will branch gradually into new species. C) most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species. D) most evolution occurs in sympatric populations. E) speciation is usually due to a single mutation. Answer: C 4) Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species. Recently, these birds have been reclassified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification? A) The two forms interbreed often in nature, and their offspring survive and reproduce well. B) The two forms live in similar habitats. C) The two forms have many genes in common. D) The two forms have similar food requirements. E) The two forms are very similar in coloration. Answer: A 5) Which of the following factors would not contribute to allopatric speciation? A) A population becomes geographically isolated from the parent population. B) The separated population is small, and genetic drift occurs. C) The isolated population is exposed to different selection pressures than the ancestral population. D) Different mutations begin to distinguish the gene pools of the separated populations. E) Gene flow between the two populations is extensive. Answer: E 6) Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be A) 12. B) 14. C) 16. D) 28. E) 56. Answer: D Test Bank for Campbell Biology in Focus Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson, Jane B. Reece 9780321813664, 9780321962751, 9780134710679
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