Biology 315 Exam 2
In the morning glory, Ipomoea purpurea, flower color is determined by genetic variation at a single codominant locus. In most natural populations this locus segregates for two alleles, P and p, with genotypes PP, Pp, and pp producing phenotypes deep purple, light purple, and white, respectively. Suppose you randomly sample plants from one such population and find the following genotypic frequencies at the flower color locus: genotype (frequency): PP (0.07); Pp (0.46); pp (0.47) What is the coefficient of inbreeding (F) for this locus in this Ipomoea population? a. -0.10 b. -0.05 c. 0.00 d. 0.05 e. 0.10
a. -0.10
quantitative variation attributable to the heritable effects of genes is measured by: a. Va b. Ve c. Vd d. Vg e. Vi
a. Va
the red queen hypothesis predicts that asexual reproduction will be most advantageous in: a. biologically simple (unchanging) communities b. biologically complex (dynamic) communities c. species with coadapted gene complexes d. species where males invest more strongly than females in progeny care e. species where females invest more strongly than males in progeny care
a. biologically simple (uncharging) communities
which of the following statements best describes the role of dominance variance (Vd) in the heritability of a quantitative trait: a. dominance effects are broken down during gamete formation and so are not heritable b. Vd increases heritability because it increases allelic interactions between loci c. Vd increases heritability because it is a genetic effect d. quantitative traits are determined by codominant loci and are not subject to the effects of Vd e. the contribution of Vd to heritability is determined by the envirnoment
a. dominance effects are broken down during gamete formation and so are not heritable
A formerly panmictic (random mating) population of tiger salamanders is divided into two smaller populations (each N = 50) by the construction of an interstate highway. Which of the outcomes listed below is likely to happen most quickly? a. drift decreases the heterozygosity within each population b. drift increases the heterozygosity within each population c. both populations go extinct due to inbreeding depression d. the formation of two new species e. drift decreases the genetic differences between the two populations
a. drift decreases the heterozygosity within each population
according to Westemeier et al., the mutational meltdown (extinction vortex) in endangered Illinois greater prairie chickens was due, in effect, to a positive feedback loop between: a. genetic drift and the expression and fixation of deleterious alleles b. genetic drift and outbreeding depression c. genetic drift and heterozygote disadvantage d. an increased rate of deleterious mutation and natural selection e. genetic drift and gene flow
a. genetic drift and the expression and fixation of deleterious alleles
Given the midparent/offspring regression plots above, which of the statements about heritability below is true? a. heritability is higher in the plot to the left because the slope of bestfit line is greater than the slope in the plot to the right b. heritability is higher in the plot to the left because the data points vary more around the line of best fit than they do in the plot to the right c. heritability is higher in the plot to the right because the slope of the bestfit line is lower than the slope in the plot to the right d. heritability is higher in the plot to the right because the data points fit more closely around the line of best fit than they do in the plot to the left e. none of the above are true
a. heritability is higher in the plot to the left because the slope of bestfit line is greater than the slope in the plot to the right
in their book The Bell Curve, authors Murray and Hernstein claimed that IQ in humans is highly heritable and that lower average IQ scores in African Americans than in European Americans is due to genetic differences between these groups. which one of the following statements best summarizes the key flaw in their arguments? a. high heritability within populations tells us nothing about the causes of differences between populations if they experience different environments b. IQ in humans in fact has no heritable genetic basis and all observed variation in IQ is due to environmental effects c. IQ in humans in fact is entirely heritable and all observed variation in IQ is genetic d. European Americans must have lower IQ than African Americans because Europeans descended evolutionarily from migrants leaving Africa between 60,000 - 125,000 years ago, and contain only a subset of the heritable variation for IQ found in Africans e. none of the above
a. high heritability within populations tells us nothing about the causes of differences between populations if they experience different environments
westemeier and colleagues supported their mutational meltdown (extinction vortex) hypothesis for the decline of the Illinois greater prairie chicken through several lines of evidence. which one of the following descriptions of this evidence is false? a. illinois prairie chickens exhibited a large excess of male as compared to female birds b. illinois prairie chickens had less diversity at six selectively neutral loci than did prairie chickens from populations in other states c. hatching success declined steadily from 1970 to 1990, in spite of increasing habitat for the prairie chickens d. hatching rates increased when prairie chickens from other, more genetically diverse, populations were transplanted to the Jasper County populations e. a comparison of DNA collected from prairie chickens in the 1990's with DNA from museum specimens collected in the 1930's and 1960's showed a loss of genetic diversity over time
a. illinois prairie chickens exhibited a large excess of male as compared to female birds
inbreeding results in inbreeding depression because: a. it increases the frequency of homozygosity and the exposure of deleterious recessive alleles to selection b. inbreeding gives people the blues c. it increases the frequency of heterozygotes and the expression of heterozygote disadvantage d. it increase the frequency of deleterious recessive alleles e. it increases the frequency of homozygosity and the expression of deleterious dominant mutations
a. it increases the frequency of homozygosity and the exposure of deleterious recessive alleles to selection
which one of the following statements regarding linkage disequilibrium is true? a. it is reduced by sexual reproduction and genetic recombination b. it exists when the coefficient of linkage disequilibrium, D, is greater than zero, but not when it is less than zero c. it is increased by crossingover during meiosis d. it is decreased by the admixture (mixing together) of two genetically differentiated populations because admixture homogenizes (evens out) gene frequencies between loci e. it is reduced by selection that favors certain combinations of genotypes
a. it is reduced by sexual reproduction and genetic recombination
in separate marshes, small populations of three species occur: grass fish, which disperse only in extreme rains and have an average dispersal of 1 individual every 45 generations, swamp rats, which occasionally disperse over land, averaging 2 individuals dispersing per generation, and marsh birds, which regularly fly from marsh to marsh, so that dispersal is extremely high. assuming that the three species are equally common, the most genetic variation within populations would be expected in: a. marsh birds, since they have the highest level of gene flow, and gene flow increases genetic variation in populations b. swamp rats, since they will have the best balance between genetic drift and gene flow, resulting in high genetic variation within populations c. grass fish, since they have the least gene flow, and gene flow introduces only selectively disadvantageous genetic variation to populations d. grass fish, since they are the best adapted to their aquatic environment and adaptation increases genetic variation in populations e. it is not possible to compare relative amounts of genetic variation in such different kinds of animals
a. march birds, since they have the highest level of gene flow, and gene flow increases genetic variation in populations
which one of the following statements is true: a. migration promotes the homogenization (evening out) of genetic variation across populations b. migration promotes divergence among populations due to differences in genotype frequencies c. migration's primary role in evolution is to promote hybridization among species d. migration is always deleterious because it counteracts the adaptive effects of natural selection e. migration is always beneficial because it helps to maintain adaptive variation within populations
a. migration promotes the homogenization (evening out) of genetic variation across populations
King (1993) studied color banding phenotypes in the water snake (Nerodia sipedon) which range from unbanned (A), to intermediately banded (B and C), to strongly banded (D). The figure below shows the observed distribution of these phenotypes along a transect from a mainland population (left) to island populations increasingly isolated in Lake Erie (right). Based on this study, which one of the following statements best describes the evolutionary processes responsible for the observed geographical pattern in color phenotypes? a. natural selection favors unbanned phenotypes on the islands, which also receive banded migrants from the mainland b. genetic drift has fixed the banded phenotype in the smell mainland population c. the island populations are accumulating mutant color phenotypes due to a Muller's Ratchet process d. genetic drift has increased variation among phenotypes in the island populations e. due to high levels of industrial waste in Lake Erie, mutation rates and, hence, variation in color phenotypes, is higher on the islands than on the mainland
a. natural selection favors unbanned phenotypes on the islands, which also receive banded migrants from the mainland
Suppose that the bumblebee pollinators of morning glory plants develop search images and tend to move back and forth between flowers of different color when foraging for pollen and nectar (e.g., from white to purple, or from purple to white colored flowers). As a result of this nonrandom foraging behavior, the inbreeding coefficient (F) measured for the flower color locus should be a. negative b. positive c. zero d. F can't be measured under these circumstances e. undefined because plants aren't actually inbreeding with one another
a. negative
imagine a population of butterflies that is in linkage equilibrium for two physically unlinked loci, one controlling forewing color (P = purple, p = red) and one controlling tail length (L = long, l = short). What sort of selection event would create linkage disequilibrium between these two loci? a. selection on a certain combination of genotypes at the two loci (e.g., only individuals that are both redwinged and longtailed die) b. selection cannot generate linkage disequilibrium between physically unlinked loci c. selection acting in a random, nonadaptive manner at each locus d. selection acting independently at each locus (e.g., whether a redwinged individual dies does not depend on its tail length) e. selection at just one locus (e.g., all red-winged individuals die)
a. selection on a certain combination of genotypes at the two loci (e.g., only individuals that are both redwinged and longtailed die)
based on the data in the figure to the right, what form of natural selection operates on birthweight in humans? a. stabilizing selection b. directional selection c. heterozygote disadvantage d. disruptive selection e. negative frequency dependent selection
a. stabilizing selection
which one of the following statements describes the genetic signature of recent positive selection on an allele? a. the allele is in high frequency and is in high linkage disequilibrium with the surrounding genome b. the allele is in high frequency and is in low linkage disequilibrium with the surrounding genome c. the allele is in low frequency and is in low linkage disequilibrium with the surrounding genome d. the allele is in low frequency and is in high linkage disequilibrium with the surrounding genome e. none of the above
a. the allele is in high frequency and is in high linkage disequilibrium with the surrounding genome
Cystic fibrosis is one of the most common serious genetic diseases among people of European ancestry. In spite of the fact that it has been lethal for most of human history, in some populations as many as 1 infant in 2,500 are born with the disease. Cystic fibrosis is caused by recessive lossoffunction alleles in a locus called CFTR that enables cells of the lung lining to ingest and destroy Pseudomonas aeruginosa bacteria. Collectively, these alleles normally have a mutation rate of about u = 0.00000067 (6.7 x 107) and selection coefficient of s = 1. Assuming that the alleles for cystic fibrosis are maintained by mutationselection balance, what is their expected frequency in the population? a. the square root of 0.00000067 b. 0.00000067 c. the square root of 0.02 d. 0.02 e. 1/2500
a. the square root of 0.00000067
sonya clegg and colleagues used genetic markers to study founder effects in a bird, the silvereye. which one of the following statements best summarizes the key finding of their research? a. there was a trend of decreasing genetic diversity going from ancestral mainland to recently colonized island populations b. there was strong positive selection favoring only a subset of ancestral alleles in newly colonized island populations c. there was a trend of increasing genetic diversity going from ancestral island populations to invasive mainland populations d. admixture among recently colonized island populations generated strong linkage disequilibrium among loci e. there was a high rate of gene flow (migration) between mainland and island populations
a. there was a trend of decreasing genetic diversity going from ancestral mainland to recently colonized island populations
suppose that a population of ruby-throated hummingbirds is under natural selection for increased beak length. if the heritability of this trait is known to be h2 = 0.25 and the response to selection (R) in the offspring generation was 0.20 cm, what was the selection differential (S) in the parental generation? a. 1.0 cm b. 0.80 cm c. 0.40 cm d. 0.20 cm e. 0 cm
b. 0.80 cm
Cystic fibrosis is one of the most common serious genetic diseases among people of European ancestry. In spite of the fact that it has been lethal for most of human history, in some populations as many as 1 infant in 2,500 are born with the disease. Cystic fibrosis is caused by recessive loss-of-function alleles in a locus called CFTR that enables cells of the lung lining to ingest and destroy Pseudomonas aeruginosa bacteria. Collectively, these alleles normally have a mutation rate of about μ = 0.00000067 (6.7 x 10-7) and selection coefficient of s = 1. Despite such strong selection, these alleles collectively persist at an observed frequency of about 0.02. Assuming random mating, what proportion of the population is expected to be carriers of (i.e., heterozygous for) cystic fibrosis? a. 2(1-0.02^2)(0.02^2) b. 2(1-0.02)(0.02) c. 2(1-(1/2500))(1/2500) d. 1/2500 e. The square root of 1/2500
b. 2(1-0.02)(0.02)
given two loci on the same chromosome, with each locus segregating for two alleles, how many different haploid chromosomal genotypes (haplotypes) are possible? a. 8 b. 4 c. 3 d. 2 e. 1
b. 4
peter buri conducted experiments on random genetic drift using about 100 experimental populations of the fruit fly, drosophila melanogaster. suppose that in each population the initial frequencies of the bw and bw75 eye color alleles were 0.4 and 0.6, respectively. how many 100 populations would you expect to eventually go to fixation for the bw75 allele under random genetic drift? a. 100 b. 60 c. 50 d. 40 e. 0
b. 60
Morran et al. (2011) tracked the outcrossing rate of three experimental lines of the CB4856 strain of the worm, C. elegans, for 30 generations. In the coevolution treatment, worms were exposed to pathogenic bacteria that had killed worms the preceding generation. In the figure below, the results for the coevolution treatment suggest that sex (outcrossing) remains beneficial indefinitely. Which one of the following statements is the best explanation for these results for the coevolution treatment? a. The worms in the coevolution treatment outcompeted the worms in the control treatment b. The worms and their pathogens were locked in an ongoing arms race, which created an ever-changing selection regime favoring the evolution of increased outcrossing and the ability to generate new genotypes. c. The worms in the evolution treatment suffered inbreeding depression whereas the worms in the coevolution treatment did not d. Outcrossing increased in the coevolution treatment because outcrossing worms were more susceptible to infection by the pathogenic bacteria. e. The control treatment indicates worms normally have a low outcrossing rate and that the evolution of higher outcrossing in the coevolution treatment was a maladaptive response to bacterial infection.
b. The worms and their pathogens were locked in an ongoing arms race, which created an ever-changing selection regime favoring the evolution of increased outcrossing and the ability to generate new genotypes
in the figure to the right, the numbers of individuals before selection are indicated by the light colored bars and the numbers of individuals after selection are indicated by the dark colored bars. based on this pattern of survival, what form of natural selection is acting on the phenotypic trait? a. heterozygote advantage b. disruptive selection c. positive frequency dependent selection d. stabilizing selection e. directional selection
b. disruptive selection
which of the following statements best describes the role of epistatic variance (Vi) in the heritability of a quantitative trait: a. the contribution of Vi to heritability is determined by the environment b. epistatic effects are broken down during gamete formation and so are not heritable c. quantitative traits are determined by multiple, independent loci and are not subject to the effects of Vi d. Vi increases heritability because it is a genetic effect e. Vi increases heritability because it increases allelic interactions between loci
b. epistatic effects are broken down during gamete formation and so are not heritable
studying genetic marker diversity in a bid, the silvereye, sonya clegg and colleagues found a reduction in genetic marker (micro satellite) diversity in recently colonized island populations relative to ancestral mainland populations. the authors interpreted this pattern as evidence of which of the following processes? a. high gene flow among island populations b. genetic drift resulting from founder effects c. a shift from sexuality to asexuality in island populations d. a reduction in mutation rates in island populations e. natural selection against heterozygotes in island populations
b. genetic drift resulting from founder effects
in discussing the "BellCurve Fallacy", your textbook explains that: a. human race-specific IQ test scores do not depend on the environment individuals of a given race experience during their lifetimes b. human race-specific differences in IQ test scores are almost impossible to attribute to genetic causes c. quantitative genetic studies of IQ test scores have proven that intelligence is the same for each of the different human races d. the techniques used to measure heritability must be modified for each race to suit their unique differences in intelligence e. quantitative genetic studies of IQ test scores have proven that there are strong differences in intelligence between the different human races
b. human race-specific differences in IQ test scores are almost impossible to attribute to genetic causes
muller's ratchet operates most effectively at decreasing the fitness of populations when: a. populations are asexual, large and mutations are each of large, deleterious effect b. populations are asexual, small and mutations are each of small, deleterious effect c. populations are sexual, small and mutations are each of small, deleterious effect d. populations are asexual, small and mutations are each of large, deleterious effect e. populations are asexual, large and mutations are each of small, deleterious effect
b. populations are asexual, small and mutations are each of small, deleterious effect
consider a locus in which the relative fitnesses of genotypes AA, Aa and aa are 1, 0.999, and 0.998, respectively. which one of the following statements is true concerning the effects of natural selection on alley frequencies at this locus? a. because the a allele is a deleterious recessive and thus more frequently expressed in small populations, selection will be more effective at increasing the frequency of the beneficial A alley in a population size 100 than in a population of size 10,000 b. selection will be more effective at increasing the frequency of the A allele in a population of size 10,000 than in a population of size 100 c. selection will increase the frequency of the A allele at the same rate in populations of size 100 and 10,000 d. because allelic variation at this locus is codominant, the deleterious a allele cannot hide in heterozygotes and so will be rapidly eliminated by selection from populations, regardless of their size e. all of the above statements are false
b. selection will be more effect at increasing the frequency of the A allele in a population of size 10,000 than in a population of size 100
in general, selection on multilocus genotypes in random-mating populations leads to linkage disequilibrium when: a. it eliminates all haplotypes from the population b. some two-locus genotypic combinations confer greater fitness than do others c. genotypes are selectively neutral d. it reduces mutation rates e. it promotes crossing-over during meiosis
b. some two-locus genotypic combinations confer greater fitness than do others
which one of the following statements concerning linkage equilibrium (and disequilibrium) is false? a. two loci are said to be in linkage equilibrium if there is a random association between the allele of the two loci in haplotypes (gametes) b. the admixture (mixing together) of two genetically differentiated populations promotes linkage equilibrium between two loci because it homogenizes (evens out) gene frequencies c. natural selection acting on individuals with different genotypes can generate linkage disequilibrium between two loci d. positive selection on new mutations can generate linkage disequilibrium between this locus and closely-linked loci e. linkage disequilibrium is reduced in each generation by the process of recombination
b. the admixture (mixing together) of two genetically differentiated populations promotes linkage equilibrium between two loci because it homogenizes (evens out) gene frequencies
the figure below shows one of the results of peter buri's experiments with fruit flies. the dots indicate the frequency of heterozygotes in each generation, averaged across all 107 fly populations. the dashed curve shows the theoretical prediction for the change in heterozygosity due to genetic drift in a population of 16 flies. the solid curve shows the prediction for a population of 9 flies. based on these results, which one of the following statements is true? a. heterozygosity is expected to decrease more rapidly across generations in populations of size 9 than of size 16 b. the experimental fly populations experienced a rate of genetic drift higher than expected for a population of size 16 c. heterozygosity decreases across generations in small populations d. the experimental fly populations experienced a rate of genetic drift lower than expected for a population of size 16 e. initially, the average heterozygosity was 0.5
b. the experimental fly populations experienced a rate of genetic drift higher than expected for a population of size 16.
which one of the following statements about the effects of random genetic drift is true? a. genetic drift is random and so does not increases or decrease the frequency of an allele over time b. the larger the population size, the slower the rate of allele fixation or loss c. the large the population size, the faster the rate of allele fixation or loss d. in random mating population there is no random genetic drifts e. in relatively large populations (containing more than a few hundred individuals) there is no random genetic drift
b. the larger the population size, the slower the rate of allele fixation or loss
consider a population of platypus in which beak width is completely heritable. if a particular mating pair's beak widths are 3.75 cm and 3.25 cm, what is the expected beak width of their offspring? a. < 3.25cm b. 3.25 cm c. 3.5 cm d. 3.75 cm e. > 3.75 cm
c. 3.5 cm
Each of the figures A, B, and C, to the right, illustrates the results of a series of computer simulations of changes in allele frequency in a group of populations subject only to the effects of random genetic drift. Choose the one answer below that best completes the following two statements: Figure _____ most likely represents the simulations performed on the largestpopulations; Figure _____ most likely represents the simulations performed on intermediatesizedpopulations; Figure _____ most likely represents the simulations performed on the smallest populations. a. C; A; B b. C; B; A c. A; C; B d. A; B; C e. B; C; A
c. A; C; B
A friend of yours is a poultry farmer who is trying to increase the size of her chickens to maximize profits. She measures the midparent and midoffspring height of some of these chickens and presents these data to you in the scatterplot to the right, which includes the best fit regression line. Based on these data, what is the best advice that you can give to her? a. There is plenty of variation, but the additive heritable variation is being masked by epistatic interactions. To maximize profits, she needs to breed out the epistatic interactions first, then redo her measurements b. There is plenty of variation, and most of it is heritable. To maximize profits, she should select the tallest individuals to breed for the next generation. c. There is plenty of variation, but none of it is heritable. To maximize profits, she should consider looking for environmental factors that influence height. d. There is plenty of variation, but only some of it is heritable. To maximize profits, she should looking for both environmental factors that influence height and select the tallest individuals to breed for the next generation. e. There really isn't any variation in the graph above. Your friend's best bet is to continue doing what she's been doing and wait for some favorable mutations to arise
c. There is plenty of variation, but none of it is heritable. To maximize profits, she should consider looking for environmental factors that influence height.
in terms of casual components of phenotypic variation, narrow-sense heritability (h2) is defined as: a. Va b. Vg c. Va / (Va + Vd + Vi + Ve) d. Vg / (Va + Vd + Vi + Ve) e. Va + Vg
c. Va / (Va + Vd + Vi + Ve)
john maynard smith addressed the question of which reproductive mode is better - sexual or asexual- by developing a null model that explores, under the simplest possible rules, the fate of a population in which some females reproduce sexually and other reproduce asexually. dunbrack et al. conducted experiments with four beetles (tribolium) to test the assumptions of marynard-smith's model. which assumption of this model did they specifically test and find to be false? a. asexuals will have an inherent two-fold numerical advantage over sexual b. sexuals produce equal number of sons and daughters c. a females reproductive mode does not affect the probability that her offspring will survive d. a females reproductive mode does not affect the number of offspring she can produce e. sexuals will produce genetically more variable offspring than asexuals
c. a female's reproductive mode does not affect the probability that her offspring will survive
suppose two populations of desert tortoise are evolving only via the process of genetic drift, with one population having 30 individuals and the other 150 individuals. which one of the following statements concerning these two populations is most likely to be true true? a. it is easier to predict which alleles will become fixed in the population of 30 individuals than in the population of 150 individuals b. the same alleles will become fixed in both populations, but will become fixed more quickly in the population of 30 individuals c. alleles are more likely to become fixed within 100 generations in the population of 30 individuals than in the population of 150 individuals d. the same alleles will become fixed in both populations, but will become fixed more quickly in the population of 150 individuals e. it is harder to predict which alleles will become fixed in the population of 30 individuals than in the population of 150 individuals
c. alleles are more likely to become fixed within 100 generations in the population of 30 individuals than in the population of 150 individuals
in examining a small population for deviations from HardyWeinberg equilibrium you find that the inbreeding coefficient (F) calculated for a single locus has a significant negative value. which one of the following processes would you hypothesize as being consistent with this result? a. heterozygote disadvantage b. positive assortative mating c. heterozygote advantage d. mating between close relatives e. random genetic drift
c. heterozygote advantage
muller's ratchet is LEAST effective at decreasing the fitness of populations when: a. populations are asexual, small, and mutations are each of small, deleterious effect. b. populations are asexual, small, and mutations are each of large, deleterious effect. c. populations are asexual, large, and mutations are each of large, deleterious effect d. populations are asexual, large, and mutations are each of small, deleterious effect. e. none of the above
c. populations are asexual, large, and mutations are each of large deleterious effect
curt lively studied rates of trematode worm infection in populations of a snail species that has both sexual and asexual females. some lively's results are shown in the figure to the right. lively interpreted these results as consistent with which one of the following statements? a. trematode infection converts females to males, thus increasing the frequency of males b. sexual females are more sensitive to trematode parasites than are males c. sexual reproduction, which produces both males and females, occurs at higher frequency in locations where total rates of trematode infections are high d. males attract trematode parasites so that the higher the frequency of males, the better asexual snails do e. males are especially sensitive to trematode infection
c. sexual reproduction, which produces both males and females, occurs at higher frequency in locations where total rates of trematode infections are high
consider two sister species of lizards; one of these species is sexual and the other is asexual. Under the Red Queen Hypothesis, if both of these species are host to a shortlived, species of parasite with deleterious consequences for fitness, which of the two lizard species will be least likely to go extinct and why? a. the asexually reproducing species are equally as likely to go extinct as the sexual species because the Red Queen Hypothesis only applies to host parasite interactions with similar generation times b. the asexually reproducing species will be less likely to go extinct because the effective population size of asexual species is higher, and a faster rate of reproduction will allow the asexual lizards to out evolve their parasites c. the sexually reproducing species will be less likely to go extinct because each generation sexual recombination will produce new multiple locus genotypic combinations to which the parasite cannot rapidly adapt d. The asexually reproducing species will be less likely to go extinct because asexual recombination will produce new multiple locus genotypic combinations to which the parasite cannot rapidly adapt e. the sexually reproducing species will be less likely to go extinct because the effective population size of sexual species is lower, so that it maintains less genetic variation to which the parasites can adapt
c. the sexually reproducing species will be less likely to go extinct because each generation sexual recombination will produce new multiple locus genotypic combinations to which the parasite cannot rapidly adapt
consider an infinitely large population with a coefficient of linkage disequilibrium of D= 0.16. in the absence of destabilizing evolutionary forces, how many generations of random recombinations (r=0.5) will be required in order for this population to reach D = 0.02? a. many b. four c. three d. two e. one
c. three
assuming that a trait is at least partially heritable, additive genetic variation is expected to be HIGHEST for traits: a. under directional selection b. under balancing selection c. under disruptive selection d. that are inherited without fail from one generation to the next (such as legs) e. subject to the greatest dominance and epistatic effects
c. under disruptive selection
In the morning glory, Ipomoea purpurea, flower color is determined by genetic variation at a single codominant locus. In most natural populations this locus segregates for two alleles, P and p, with genotypes PP, Pp, and pp producing phenotypes deep purple, light purple, and white, respectively. Suppose you randomly sample plants from one such population and find the following genotypic frequencies at the flower color locus: genotype(frequency): PP (0.18); Pp (0.44); pp (0.38) what is the coefficient of inbreeding (F) for this locus in this population? a. -0.17 b. -0.08 c. 0.00 d. 0.08 e. 0.17
d. 0.08
Suppose you are a plant breeder interested in improving a particular horticultural species by increasing the width of its flowers. To determine the heritability of this trait, from a population with a mean corolla width of 2 cm, you select as parents for the next generation a subpopulation with a mean corolla width of 2.25 cm. In the following generation, you find the mean corolla width of the offspring of the selected parents to be 2.1 cm. What is the narrow-sense heritability (h2) of this trait? a. 0.10 b. 0.15 c. 0.24 d. 0.40 e. 0.60
d. 0.40
gene flow between demes (populations) tends to: a. increase genetic variation within individual demes b. decrease genetic variation within individual demes c. make different demes more genetically similar to each other d. a & c e. b & c
d. a & c
suppose you are a conservation biologist and believe that a small population of a rare and endangered species you are responsible for preserving is declining because it has become subject to a mutational meltdown (extinction vortex). to test this hypothesis, you introduce into this population a number of individuals collected from other populations. if the mutational meltdown hypothesis is correct then, as a result of your experiment you would expect to see: a. increase in the mutation rate in the population in subsequent generations b. a measurable increase in the rate of Muller's Ratchet c. a decrease in the populations allelic diversity d. an increase in survival and reproductive success in the population in subsequent generations e. an increase in the incidence of disease in the population in subsequent generations
d. an increase in survival and reproductive success in the population in subsequent generations
In the water snake (Nerodia sipedon), the frequency of banded snakes decreases and unbanded snakes increases as one moves from the mainland out to islands in Lake Erie. Based on research by King and colleagues, what best explains this spatial pattern? a. unbanded snakes are continually migrating out from the mainland while banded snakes are continually migrating from the islands to the mainland b. genetic drift promotes the random fixation of the allele for unbanded coloration in small island populations c. linkage disequilibrium between the locus controlling coloration and a locus controlling dispersal capability d. banded snakes are continually migrating out from the mainland while unbanded snakes are favored by directional selection on the islands e. genetic drift and inbreeding depression in small island populations promote mutation from the wild-type allele for banded coloration to the allele for unbanded coloration
d. banded snakes are continually migrating out from the mainland while unbanded snakes are favored by directional selection on the islands
if, for many generations, individuals who are taller than average in a population survive and reproduce better than individuals at or below average, and height is heritable, we would have: a. selection for an intermediate equilibrium height b. heterosis for height c. stabilizing selection for height d. directional selection for height e. disruptive selection for height
d. directional selection for height
the interplay between gene flow (migration) and selection can maintain genetic variation within a local population if: a. directional selection works against an allele in the local population and that allele is absent in migrants from other populations b. directional selection works against an allele in the local population and that allele is disadvantageous and rare in other populations c. directional selection favors an allele in the local population and that allele is in high frequency in migrants from other populations d. directional selection works against an allele in the local population but that allele is continually introduced by migration from other populations e. directional selection favors an allele in the local population and that allele is carried by migrants from this population to other populations
d. directional selection works against an allele in the local population but that allele is continually introduced by migration from other populations
random genetic drift affects processes occurring both within and among populations. which one of the following statements about the expected affects of genetic drift is false? a. drift increases levels in inbreeding within populations b. drift decreases levels of heterozygosity within populations c. drift decreases levels of allelic diversity within populations d. drift decreases differentiation among populations e. all of the above statements are true
d. drift decreases differentiation among populations
which one of the following processes homogenizes (evens out) genetic variation among populations: a. natural selection b. random genetic drift c. mutation d. gene flow e. none of the above
d. gene flow
in separate marshes, small populations of three species occur: grass fish, which disperse only in extreme rains and have an average dispersal of 1 individual every 45 generations, swamp rats, which occasionally disperse over land, averaging 2 individuals dispersing per generation, and marsh birds, which regularly fly from marsh to marsh, so that dispersal is extremely high. assuming that the three species are equally common, the most genetic DIFFERENTIATION between populations would be expected in: a. it is not possible to compare relative amounts of genetic variation among such different kinds of animals b. grass fish, since they are the best adapted to their aquatic environment, and adaptation increases genetic variation among populations c. swamp rats, since they will have the best balance between genetic drift and gene flow, resulting in high genetic variation among populations d. grass fish, since they have the least gene flow, and gene flow acts to decrease genetic variation among populations e. marsh birds, since they have the highest level of gene flow, and gene flow increases genetic variation among populations
d. grass fish, since they have the least gene flow, and gene flow acts to decrease genetic variation among populations
doug emien's study of horn length variation in male dung beetles found that male-male competition favored ___________ horns while sneaky sexual strategies favored _________ horns, making this an example of _________ selection a. longer; shorter; stabilizing b. longer; longer; disruptive c. shorter; longer; disruptive d. longer; shorter; disruptive e. shorter; longer; stabilizing
d. longer; shorter; distruptive
consider a woman who is the last in a long line of inbreeders from iowa city. despite manifesting stere effects of inbreeding, including banjo picking, she has nonetheless managed to lure an unrelated and otherwise intelligent man from ames into marrying her and fathering her child. given this scenario, which of the following statements is true? a. the child is half as inbred as the mother b. the child will suffer inbreeding depression due to the increased expression of deleterious recessive mutations c. the child's genotype will be unusually homozygous d. none of the above e. all of the above
d. none of the above
based on the following gametic frequencies, which of the following populations are in linkage equilibrium? population 1: 0.32, 0.48, 0.08, 0.12 population 2: 0.2, 0.3, 0.3, 0.2 population 3: 0.35, 0.15, 0.35, 0.15 a. population 1 b. population 2 c. population 3 d. populations 1 and 3 e. populations 2 and 3
d. populations 1 and 3
when two loci are in linage equilibrium, which one of the following statements is true? a. all possible halotypes occur at equal frequency b. allele frequencies will not change over time c. the two loci do not interact d. the frequency of each haplotype can be calculated simply by multiplying the frequency of its two alleles e. all of the above are true
d. the frequency of each haplotype can be calculated simply by multiplying the frequency of its two alleles
recall clausen, keck, and hiesey's experimental showing that plants from a single population of yarrow (achillea) exhibit very different phenotypic variance (e.g., for height) when grown at different geographic locations. these experiments demonstrate that: a. the phenotypic expression of the underlying genotype is independent of the environment in which it is expressed b. the phenotypic variance (Vp) is not an important component of the narrow sense heritability c. the techniques used to measure heritability must be modified to suit the conditions of different environments d. the narrow sense heritability (h2) of a trait is environmentally dependent e. the narrow sense heritability (h2) of natural populations is constant, regardless of the environment in which it is grown
d. the narrow sense heritability (h2) of a trait is environmentally dependent
which of the following is an accurate definition of the inbreeding coefficient, F: a. the probability that an individual carries an allele descended from a recent ancestor b. the probability that an individual mates with a close relative c. the probability that two individuals share an allele identical by descent from a recent common ancestor d. the probability that an individual carries two copies of an allele identical by descent from a recent common ancestor e. the probability that an individual mates with another individual of the same genotype
d. the probability that an individual carries two copies of an allele identical by descent from a recent common ancestor
zhang et al. (2011) studied the evolution of salt tolerance in the fruit fly. the experimental populations consisted of an original inbred line and six lines derived from it over the course of 30 generations: two unstressed lines and four salt stressed lines. at the end of the 30 generations, each line was evaluated for tolerance to 5% table salt in diet. the results are summarized in the figure to the right. which one of the following conclusions is true? a. the original inbred stock had the highest salt tolerance b. because they were not stressed, the unstressed lines evolved higher salt tolerance than the salt-stressed lines c. because they were stressed, the salt-stressed lines had the lowest salt tolerance d. the salt-stressed lines accumulated mutations that enabled them to evolve the highest salt tolerance e. none of the above statements are true
d. the salt-stressed lines accumulated mutations that enabled them to evolve the highest salt tolerance
suppose that in morning glory the only violation of Hardy-Weinberg assumptions is nonrandom mating due to pollinator movement among flowers of the same color (e.g., white to white or purple to purple). In this case, a randomly selected locus from the morning glory genome (i.e., independent of the flower color locus) will have an inbreeding coefficient (F) that is: a. positive b. negative c. undefined because plants aren't actually inbreeding with one another d. zero e. F can't be measured under these circumstances
d. zero
spinal muscular atrophy is, after cystic fibrosis, the second most common lethal or near lethal recessive disease in caucasians. this disease is caused by recessive loss of function alleles at the telSMN locus, which, collectively, have a mutation rate of about 10^-4 and selection coefficient of 0.9. what is the collective frequency of these alleles at mutation-selection balance? a. 0 b. 0.50 c. 0.0001 d. 0.00011 e. 0.01
e. 0.01
in the morning flory, Ipomoea purpurea, flower color is determined by genetic variation at a single codominant locus. in most natural populations this lock segregates for two alleles, P and p, with genotypes PP, Pp, and pp producing phenotypes deep purple, light purple, and white, respectively. Suppose you randomly sample plants from one such population and find the following genotypic frequencies at the flower color locus: genotype(frequency): PP(0.42); Pp(0.36); pp(0.22) What is the coefficient of inbreeding (F) for this locus in the Ipomoea population? a. -0.25 b. -0.06 c. 0.00 d. 0.06 e. 0.25
e. 0.25
which one of the following statements about mutationselection balance involving deleterious alleles is true: a. mutation-selection balance occurs only when deleterious mutations are completely eliminated from a population b. mutation-selection balance occurs when genotypic variation at a locus is selectively neutral c. mutation-selection balance results when all alleles have equal fitness d. mutation-selection balance results when the mutation rate for an allele and the selection coefficient against it are equal to each other e. mutation-selection balance results when the rate at which a population gains an allele by mutation and the rate the rate at which the allele is removed by selection are equal to each other
e. mutation-selection balance results when the rate at which a population gains an allele by mutation and the rate the rate at which the allele is removed by selection are equal to each other
which one of the following statements IS a prediction of the Red Queen Hypothesis? a. there is a two-fold cost of sexual reproduction relative to asexual reproduction b. asexual reproduction confers the greatest resistance to rapidly evolving parasites and pathogens because it best preserves successful multi locus genotypes c. since "it takes all the running you can do to stay in place" evolutionarily, a species must have high rates of migration and gene flow d. asexual lineages have higher extinction rates than sexual ones e. sexual reproduction should be favored over asexual reproduction in rapidly changing environments
e. sexual reproduction should be favored over asexual reproduction in rapidly changing envirnoments
in abrahamson et al. 's study of goldenrod stem galls caused by the larvae of the fly Eurosta, they found that parasitic wasps selected against larvae in ___________ galls while avian predators selected against larvae in _______ galls, making this an example of _______ selection
e. smaller; larger; stabilizing
gene flow is best defined as: a. the movement of genetic material from the nucleus to the cytoplasm b. the movement of gene loci from one chromosome to another c. the transmission of genetic information from parent to the offspring d. the movement of alleles within a population e. the movement of alleles between populations
e. the movement of alleles between populations
