IB 150 Exam 3 Homework

You sampled 1000 individuals from a population of mosquitoes to test whether they are in Hardy-Weinberg Equilibrium for a gene D, where a recessive allele (d) is responsible for conferring pesticide resistance. After genotyping your 1000 sampled mosquitoes, go obtain the following number of individuals for the three possible genotypes: Genotype dd: 22 individuals Genotype Dd: 188 individuals Genotype DD: 790 individuals Assuming that this population of mosquitoes does NOT violate any Hardy-Weinberg assumptions in the next generation, what % of the population do you predict will show the recessive phenotype of being DDT resistant?

1.3

In Chen caerulescens (a species of goose), the white phenotype (snow goose) and the dark phenotype (blue goose) occasionally coexist. In these areas of contact, white-by-white and blue-by-blue matings are much more common than white-by-blue matings. Based on this observation alone, you .... Select all that apply: Select one or more: a. ... would predict that heterozygous genotypes are rare in these populations. b. ... would predict that these populations are in Hardy-Weinberg Equilibrium. c. ... would predict that the allele associated with the light phenotype will become more common. d. ... would predict that homozygous genotypes are rare in these populations. e. ... would predict that the frequency of alleles associated with the dark and light phenotypes will remain relatively similar. f. ... would predict that the allele associated with the dark phenotype will become more common.

a. ... would predict that heterozygous genotypes are rare in these populations. e. ... would predict that the frequency of alleles associated with the dark and light phenotypes will remain relatively similar.

Monkey flowers (Mimulus guttatus) living near the sites of copper mines can grow in soil containing high concentrations of copper, which is toxic to most plants. Copper tolerance is a heritable trait, and in several sites near old copper mines, the allele conferring copper tolerance has become fixed. Which statement is correct? Select one: a. Prior to mining, the population contained both copper-tolerant and copper-intolerant plants b. High mutation rates resulted in the fixation of the copper-tolerance allele c. Copper contamination in the soil created copper-tolerant plants d. Once mining began, mutation created the copper-tolerant allele that the plants needed to survive

a. Prior to mining, the population contained both copper-tolerant and copper-intolerant plants

Which of the following statements about Population 2 in the preceding question is true, assuming many generations have passed, and no new alleles have been introduced in the intervening time that affect the illustrated phenotypic trait? Select one: a. The mean of the phenotypic distribution for Population 2 will eventually settle around the fitness optimum 2, because natural selection would select against intermediate phenotypes, preventing the population mean to migrate toward the fitness optimum 1 from its current distribution. b. The mean of the phenotypic distribution for Population 2 will eventually settle around the fitness optimum 2, because natural selection cannot operate without mutations. c. The mean of the phenotypic distribution for Population 2 will shift toward ever higher values of the phenotypic trait, because natural selection is a predictable process that favors the best and largest individuals. d. The mean of the phenotypic distribution for Population 2 will eventually settle around the fitness optimum 1, because natural selection guarantees that populations evolve toward the trait associated with the highest fitness.

a. The mean of the phenotypic distribution for Population 2 will eventually settle around the fitness optimum 2, because natural selection would select against intermediate phenotypes, preventing the population mean to migrate toward the fitness optimum 1 from its current distribution.

In a particular recessive genetic disorder, you find the allele frequency for this recessive allele in a population is 0.02. Assuming the population is in Hardy-Weinberg Equilibrium over the last generation, which of the following are possible statements about this population? Select all that apply. Select one or more: a. The population under investigation could have been formed by a founder event several hundred years ago. b. This genetic disorder could display severe and potentially fatal health complications only in individuals above 50 years of age. c. Most of the recessive alleles are found in heterozygous individuals. d. Any individuals in this population that are homozygous recessive are sterile.

a. The population under investigation could have been formed by a founder event several hundred years ago. b. This genetic disorder could display severe and potentially fatal health complications only in individuals above 50 years of age. c. Most of the recessive alleles are found in heterozygous individuals.

Which of the following scenarios is well illustrated by the fitness landscape shown in the top panel of the figure in question 11? The relevant phenotypically variable trait to be considered is shown in bold for each scenario below. Select all that apply: Select one or more: a. There are two populations of the hawthorn fly, Rhagoletis pomonella, in the U.S., that differ in the timing of emergence and egg-laying: the emergence of individuals of one population are timed to the hawthorn tree and a second population is timed to apple trees, which fruit about 3-4 weeks earlier than hawthorn trees. b. Two populations of lungless salamanders of the species Ensatina eschscholtzii are separated by the Sacramento valley, and have evolved differing spotting patterns since their populations became geographically isolated ten thousand years ago. Transplant experiments show no convincing evidence that presence or absence of spots affects reproductive success of salamanders in either geographic area. c. Two populations of anoles differ in the length of their hind limbs, with populations living at ground-level having relatively longer limbs than individuals spending most of their time on vertical tree trunks. Experimental evidence indicates that the average limb length of each population corresponds to high maneuverability in the preferred habitat of each population. d. Two populations of Lord Howe Palms differ in the average time of year during which they flower, with thatch palms flowering on average 1.5 months before curly palms begin to flower. While hybrids are perfectly viable, hybrids are rarely encountered and display an intermediate flowering time that does not overlap much with either of the parent populations.

a. There are two populations of the hawthorn fly, Rhagoletis pomonella, in the U.S., that differ in the timing of emergence and egg-laying: the emergence of individuals of one population are timed to the hawthorn tree and a second population is timed to apple trees, which fruit about 3-4 weeks earlier than hawthorn trees. c. Two populations of anoles differ in the length of their hind limbs, with populations living at ground-level having relatively longer limbs than individuals spending most of their time on vertical tree trunks. Experimental evidence indicates that the average limb length of each population corresponds to high maneuverability in the preferred habitat of each population. d. Two populations of Lord Howe Palms differ in the average time of year during which they flower, with thatch palms flowering on average 1.5 months before curly palms begin to flower. While hybrids are perfectly viable, hybrids are rarely encountered and display an intermediate flowering time that does not overlap much with either of the parent populations.

Which of the following best defines biological evolution within a population? Select one: a. change in allele frequencies over time b. natural selection c. survival of the fittest d. phenotypic change within an individual's lifetime

a. change in allele frequencies over time

While generation of heritable variation via ___________ is random, changes in the frequency of this variation in a population due to _____________ is highly non-random! Select one: a. mutations; natural selection b. meiosis; pre-zygotic isolation c. meiosis; founder events d. sexual reproduction; non-random mating e. mutations; genetic drift

a. mutations; natural selection

The sub-discipline of psychology, called evolutionary psychology, assumes that many (or in some cases even all) common human behaviors are evolutionary adaptations (including criminal behaviors, different cheating patterns between sexes, altruism - helping others without expecting a repayment, etc.). As an evolutionary biologist, you recommend a more cautious approach rather than expecting all human behaviors to be an adaptation (a result of natural selection), because.... Select all that apply: Select one or more: a. not all phenotypic (including behavioral) traits are heritable b. natural selection is not guaranteed under all conditions c. learned behaviors (acquired by observing others during their lifetime) are not subject to evolution d. not all phenotypic (including behavioral) traits affect the reproductive success of individuals e. behavior never has a heritable basis

a. not all phenotypic (including behavioral) traits are heritable b. natural selection is not guaranteed under all conditions c. learned behaviors (acquired by observing others during their lifetime) are not subject to evolution d. not all phenotypic (including behavioral) traits affect the reproductive success of individuals

Use the Hardy-Weinberg principle to predict expected numbers of individuals for each genotype, if the null-hypothesis is true, and this population is NOT evolving, then use a Chi-Square test to determine the p-value for this null-hypothesis to support your conclusion. Select one: a. p<0.05; conclude that population is not in Hardy-Weinberg b. p<0.01; conclude that population is not in Hardy-Weinberg c. p>0.05; conclude that population is in Hardy-Weinberg d. p<0.05; conclude that population is in Hardy-Weinberg e. p<0.01; conclude that population is in Hardy-Weinberg f. p>0.01; conclude that population is not in Hardy-Weinberg

a. p<0.05; conclude that population is not in Hardy-Weinberg 1. Determine observed allele frequencies by counting them up and dividing by the total number of alleles present in your sample (2000 in this case). In this case p=0.884 and q=0.116. 2. Once you have your observed allele frequencies for your sampled mosquitoes, determine the EXPECTED genotype frequencies IF this population were to be in Hardy-Weinberg Equilibrium, by using the H-W Equation. In this case, you get for expected genotype frequencies: DD: 0.781456; Dd: 0.205088; dd: 0.013456. 3. Convert these expected frequencies into the expected numbers of individuals for the same sample size of 1000 mosquitoes. In this case: DD: 781.5; Dd: 205; dd: 13.5. 4. Calculate the Chi-square value by comparing your Observed and Expected number of individuals. In this case, the Chi-Square value is 6.94, and the degrees of freedom are 2. 5. Use the Chi-square table to determine the associated p-value for your null hypothesis that the differences between observed, and expected if population is in HW-Equ. are only due to chance. In this case p<0.05. This means that the likelihood that the differences between observed and expected being just due to random error is less than 5%, so we have to conclude that in all likelihood something causes them to be systematically different - i.e. We need to conclude that some mechanism is violating assumptions of the Hardy-Weinberg Principle in this population of mosquitoes. They are evolving with respect to the DDT resistance gene.

What do you predict is the likelihood for a female in the US population to show phenotypic symptoms of color-blindness? Select one: a. 0.1472 b. 0.0064 c. 0.16 d. 0.08

b. 0.0064 In order for a female to show symptoms of red-green color blindness, she would need to be homozygous recessive. Given that the allele frequency for the recessive allele, q, is 0.08 in the US population, the predicted frequency for female homozygous recessive individuals is 0.0064, or the probability to inherit one recessive allele at probability 0.08, AND a second allele, also at frequency 0.08. That means, the frequency to be homozygous recessive for females is 0.08*0.08 = 0.0064.

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.81 and q = 0.19 for a particular gene? Select one: a. AA = 0.250, Aa = 0.500, and aa = 0.250 b. AA = 0.656, Aa = 0.308 and aa = 0.036 c. AA = 0.333, Aa = 0.333 and aa = 0.333 d. AA = 0.900, Aa = 0.785 and aa = 0.436 e. AA = 0.810, Aa = 0.154 and aa = 0.190

b. AA = 0.656, Aa = 0.308 and aa = 0.036

Claytonia virginica is a woodland spring herb with flowers that vary from white to pale pink to bright pink. This plant is primarily pollinated by a bee that prefers pink flowers to white flowers. As a result, Claytonia with pink flowers have greater relative fruit set than Claytonia with white flowers due to greater pollination rates. Nevertheless, the percentage of different flower colors remains stable in the study population from year to year. Which of these statements might explain this observation? Select one: a. Reproductive success is not a good measure for fitness in this species. b. Flower color is not heritable but is instead determined by the pH of the soil. c. Fitness is primarily determined by fruit set in this species. d. The white flowers have evolved pollinator resistance.

b. Flower color is not heritable but is instead determined by the pH of the soil.

Altruistic behavior (helping others without repayment) is a human behavioral trait that is relatively uncommon in other species, especially in cases like the adoption of an unrelated orphaned child. Raising an unrelated child takes a large amount of time and material resources that are hence not available to the raising of a biological offspring, so you might expect these behaviors to be selected against if they had a heritable basis. Evolutionary psychology nevertheless has tried to explain altruistic behavior in humans as an adaptation, in other words as a direct result of natural selection. IF the hypothesis is correct that adoption of unrelated children IS a human behavior that evolved as a result of natural selection, which of the following scenarios would be consistent with this explanation? Select one: a. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are smarter because they are planning to increase their own relative fitness. b. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are more likely to lose biological offspring to accidents or mishaps as well. c. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are not helping our human species to be successful and survive. d. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are not really considering the consequences of their actions for the benefit of society. e. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are not good people.

b. Humans that lack the strong emotional feeling of empathy that causes them to want to protect children (including unrelated ones) are more likely to lose biological offspring to accidents or mishaps as well.

Did the allele frequencies change from the original population in Question 8 to your predicted offspring generation in Question 9? Select one: a. Yes b. No

b. No

What is the most likely mechanism that can account for this pattern? Select one: a. Natural Selection against the deleterious allele. b. Outcrossing due to increasingly common marriages between Hutterites and non-Hutterites in recent decades. c. Inbreeding due to strict isolation of this small community, causing most individuals to be related on at least second to third cousin level. d. Natural selection against the homozygous recessive genotype only. e. Genetic Drift due to several centuries of being a very isolated, small community.

b. Outcrossing due to increasingly common marriages between Hutterites and non-Hutterites in recent decades.

Use the information on allele frequencies in three populations to select the correct statement. Population A: p-1, q-0 Population B: p-0.60, q-0.40 Population C: p-0, q-1 Select one: a. Repeated mutation has resulted in the loss of the allele represented by allele frequency p in population C b. Population B has more genetic diversity than does population C c. The rate of evolution will be faster in population A relative to population B d. Because p + q = 1 in all populations, all populations have the same amount of genetic diversity

b. Population B has more genetic diversity than does population C

Three-spined stickleback fish (Gasterosteus aculeatus) show substantial heritable variation in gill raker length. Fish caught in open water tend to have longer gill rakers and eat different foods than do those caught in shallower water. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a lake with a high density of these fish? Select one: a. directional selection b. disruptive selection c. stabilizing selection d. no selection e. sexual selection

b. disruptive selection

White-tufted ear marmosets are small primates with tufts of long white hair on their ears. You observe that males vary in the length of their ear tufts. You wonder whether having longer ear tufts is adaptive to these males. In order to test this hypothesis, you should... Select all that apply: Select one or more: a. determine whether longer ear-tufted males are older b. look for evidence that longer ear-tufted males leave more offspring c. determine if ear tuft length is heritable d. determine whether males with shorter ear tufts are less aggressive e. determine whether longer ear-tufted males also tend to grow to a bigger body mass

b. look for evidence that longer ear-tufted males leave more offspring c. determine if ear tuft length is heritable

Which of the following is a prediction of the Hardy-Weinberg principle? Select one: a. Natural selection acts on standing variation b. Certain traits are heritable c. Expected genotype frequencies can be determined from allele frequencies d. Individuals with higher fitness produce more offspring e. Mutations can cause alleles to become fixed in a population

c. Expected genotype frequencies can be determined from allele frequencies

Prior to the Mongolian invasions which occurred between the 13th and 16th centuries, the frequency of blood type B across Europe was close to zero, based on genetic analyses of DNA extracted from ancient skeletal remains. The frequency of blood type B among the Mongols was relatively high. Today, we observe high frequencies of blood type B in the Eastern European countries and a gradual decrease in the frequency of blood type B as one moves from the Eastern European countries to the Western European countries, such as France and England. Which process is responsible for the resulting pattern? Select one: a. Negative assortative mating between Mongolian invaders and native Europeans. b. Genetic Drift due to founder effect among invading Mongol populations. c. Gene flow between Mongolian invaders and native European populations. d. Positive assortative mating between Mongolian invaders and native Europeans. e. Mutation of the IA to the IB allele in native European populations. f. Natural selection for the IB allele.

c. Gene flow between Mongolian invaders and native European populations.

The Hardy-Weinberg equation is p2 + 2pq + q2 = 1. What does the fact that the genotype frequencies add up to 1 demonstrate? Select one: a. That natural selection is acting on a gene b. That the population is evolving c. That the frequencies of each genotype have been determined correctly d. That allele frequencies are not changing e. That mutation is acting on a gene

c. That the frequencies of each genotype have been determined correctly

Many pure-bred dog breeds suffer from congenital conditions, while mutts (mixed-breed dogs that are hybrids between different pure-bred breeds) show far fewer congenital conditions. Which of the following statements is likely true about this observation? Select all that apply. Select one or more: a. Crosses between different genetically distinct dog breeds result in an offspring population that is in Hardy-Weinberg Equilibrium. b. Random mating in mutts decreases the likelihood that offspring from two mutts are carriers for recessive congenital conditions compared to offspring from crosses involving two purebred dogs of the same breed. c. The small founding population of many dog breeds is a likely reason for the unusually high frequency of deleterious alleles in dogs from pure-bred breeds. d. Crosses between different genetically distinct dog breeds result in an offspring population with a higher frequency of heterozygotes than predicted by 2pq. e. Re-established gene flow between pure-bred populations reintroduces non-deleterious alleles into the mutt population. f. Deleterious recessive alleles are less likely to be passed to offspring of mutts.

c. The small founding population of many dog breeds is a likely reason for the unusually high frequency of deleterious alleles in dogs from pure-bred breeds. d. Crosses between different genetically distinct dog breeds result in an offspring population with a higher frequency of heterozygotes than predicted by 2pq. e. Re-established gene flow between pure-bred populations reintroduces non-deleterious alleles into the mutt population.

Why does natural selection prevent a population from remaining in Hardy-Weinberg equilibrium? Select one: a. dominant alleles always reach fixation b. certain alleles increase due to chance c. certain alleles increase because they increase reproductive success d. new alleles enter one population from another e. new alleles are created based on the need of the population

c. certain alleles increase because they increase reproductive success

Red-green color blindness is an X-linked, recessive trait. Approximately 8% of men in the US population show red-green color blindness in their phenotype. What is your best estimate for the frequency of the color-blindness-causing allele in the US population? Select one: a. 0.0064 b. 0.16 c. 0.28 d. 0.08 e. 0.1472

d. 0.08 because men only receive a single allele for X-linked traits, they actually show the allele frequency of the overall population in their phenotype already!

IF your hypothesis in the previous question is correct, what else can you predict as being likely true and might be able to explain why the behavioral trait "strong empathy for an urge to protect children" is so common in humans and not other species? Select one: a. Altruistic behavior cannot be a heritable trait in most other species. b. Most other species are not as smart as humans. c. Altruistic behavior cannot be a heritable trait in humans. d. Human babies are more vulnerable and in greater need of parental care than in most other species. e. Most other species are not capable of feeling empathy.

d. Human babies are more vulnerable and in greater need of parental care than in most other species.

In 2011, a patient presented with a multi-drug resistant HIV infection, including to the drug ENF. Given that all then-available drugs had lost their effectiveness at controlling the HIV infection in this patient, his doctors attempted an approach based on evolutionary medicine. The patient was taken off of all HIV medications for several weeks. During this time, HIV virus load increased in the patient's system. Three months later, the patient was placed on treatment with the drug ENF again and the virus population responded very strongly to the drug again - apparently because the HIV virus population in the patient had lost its resistance to the drug ENF. How can you explain this remarkable finding. Use your results from the previous question to help you. Select one: a. In the absence of the drug ENF, HIV mutates back to the wild-type allele of the gp41 gene, since the drug-resistant allele is no longer needed. b. In the absence of the drug ENF, additional selection pressures emerge that select for the wild-type allele. c. In the absence of the drug ENF, HIV particles of lower relative fitness are able to survive. d. In the absence of the drug ENF, one of the selection pressures fell away, and wild-type HIV particles for gene gp41 had higher fitness.

d. In the absence of the drug ENF, one of the selection pressures fell away, and wild-type HIV particles for gene gp41 had higher fitness.

In a woodland, 50% of larkspur flower (Corydalis cava) individuals have purple flowers and 50% have white flowers. Flower color is determined by a single gene with two alleles. Homozygous dominant and heterozygous individuals have purple flowers, homozygous recessive individuals have white flowers. In a hypothetical scenario, a rabbit family that eats just purple flowers moves into the woodland. When a rabbit finds a purple-flowered plant, it eats all the flowers on that plant. Although the plant survives having its flowers eaten, it produces no seeds. After many generations, .... Select one: a. The "purple" allele persists at very low allele frequency in carriers. b. The allele frequencies remain more or less the same. c. Rabbits will cause purple plants to mutate to produce a toxin that keeps rabbits from eating them. d. The allele frequency for the "white" allele is likely to become fixed.

d. The allele frequency for the "white" allele is likely to become fixed.

Reproductive isolation of 2 populations of the same species ____________. Select one: a. reduces the effects of natural selection and genetic drift b. makes it less likely the 2 populations will become distinct species c. makes their allele frequencies more similar d. allows their allele frequencies to change independently of one another e. can only be caused by either vicariance or dispersal

d. allows their allele frequencies to change independently of one another

Male house sparrows sing a different song than do male tree sparrows. Based on this information alone, what type of prezygotic isolation mechanism might be acting to keep the species separate? Select one: a. mechanical b. gametic barrier c. hybrid inviability d. behavioral e. temporal

d. behavioral

A particular recessive genetic disorder is fatal before birth, so there are no homozygous recessive individuals. In a particular population, one in 15 individuals is a carrier for this disorder. What are the allele frequencies of the dominant (p) and recessive (q) alleles in this population? Select one: a. p = 0.955, q = 0.045 b. p = 0.933, q = 0.067 c. p = 1.0, q = 0.0 d. p = 0.967, q = 0.033

d. p = 0.967, q = 0.033

_____________ is likely the most common mode of selection in populations during long periods of stasis (lack of phenotypic change). Select one: a. natural selection b. sexual selection c. directional selection d. stabilizing selection e. disruptive selection

d. stabilizing selection

Which evolutionary mechanism is most likely responsible for the unusually high frequency of the deleterious allele for CPT1A deficiency among the US Hutterite population? Select one: a. Genetic Drift due to a bottleneck event b. Sexual Selection c. steady Genetic Drift due to gametic sampling d. Gene Flow due to original Hutterite settlers arriving from Europe e. negative Assortative Mating f. Genetic Drift due to a founder event g. positive Assortative Mating h. Natural Selection

f. Genetic Drift due to a founder event