Answer the questions in the wkst in details
Biology Assignment Name 1. Imagine the following experiment on the scale-eating cichlid fish Perissodus microlepis. Three small artificial ponds are established, each containing 100 of the cichlids and an abundant supply of common prey species. Pond A contains 90 sinistral (left-handed) cichlids and 10 dextral (right-handed) cichlids. Pond B contains 50 of each type, and Pond C contains 10 sinistrals and 90 dextrals. The relative frequency of the sinistral fish at the start of the experiment is shown for each pond in the graph at right. A. Based on what you know about these fish, predict the long-term changes (over the next 20 generations or so) in the relative frequencies of sinistral fish in each of the three ponds and plot your predictions on the graph. You can plot your predictions by double-clicking on the plot and then choosing the Scribble tool under the Select line menu (3 points). B. Briefly explain your predictions in the space provided below (2 points). C. Now imagine repeating the experiment described in (A) with one important change; instead of having access to living prey, the scale-eating cichlids are maintained on a diet consisting exclusively of commercial fish food (Purina® Scale Chow). Predict the long-term changes (over the next 20 generations or so) in the relative frequencies of sinistral fish in each of the three ponds and plot your predictions on the graph. You can plot your predictions by double-clicking on the plot and then choosing the Scribble tool under the Select line menu (3 points). B. Briefly explain your predictions in the space provided below (2 points). Exam continues on next page Page 2 2. Imagine that you are studying the meadow grasshopper Conocephalus whitenacki as your senior comp project. Individuals of this species mate in early autumn and the females lay their eggs in the soil. The eggs hatch in May, and the young grasshoppers emerge from the soil and feed on grasses and other meadow vegetation until they reach adult size and sexual maturity in August. Color pattern in these grasshoppers is determined by a single gene locus with two alleles: BB homozygotes are brown, BG heterozygotes have longitudinal green and brown stripes, and GG homozygotes are green. In a sample of 700 adult grasshoppers you collected from your study population in late August, 140 were brown, 398 were striped, and 162 were green. A. Assuming that your sample of 700 grasshoppers is representative of the entire adult population, estimate the relative frequencies of the B and G alleles in the population. Show your work (2 points). B. Calculate the expected genotype frequencies under the assumption that the population of grasshoppers is in Hardy-Weinberg equilibrium, and compare the observed and expected genotype frequencies by calculating the Chi-square statistic. Do they agree? (Hints: Chi-square statistic = χ2 = ∑ [(O - E)2 / E]; χ2 critical value = 3.84). Show your work (3 points). C. If you concluded that observed and expected genotype frequencies are in close agreement, briefly explain what this tells you about the population of grasshoppers you are studying. If you concluded that observed and expected genotype frequencies are not in agreement, propose a single, specific hypothesis that would account for the disagreement, and briefly explain your hypothesis (2 points). Question 2 continues on next page Page 3 D. Now imagine that you also analyze a sample of 390 young grasshoppers that you had collected earlier in the season in late May, shortly after the young hatched from eggs. In this sample, 92 of the young grasshoppers were brown, 194 were striped, and 104 were green. Estimate the relative frequencies of the B and G alleles in this sample, calculate the expected genotype frequencies under the assumption that the population of grasshoppers is in Hardy-Weinberg equilibrium, and compare the observed and expected genotype frequencies by calculating the Chi-square statistic. Show your work (5 points). E. Now revisit your answer to parts (C) and (D) and try to reconcile them. In other words, do the data for young grasshoppers (D) support or contradict the conclusions / hypothesis you made in part (C) for adult grasshoppers? Briefly explain your reasoning (3 points). 3. The evolution of antibiotic resistance in disease-causing bacteria is a serious public health problem. Here is a statement from the website drugs.com (https://www.drugs.com/cg/antibiotic-resistant-bacteria.html) regarding the issue: “When antibiotics are not used correctly, they may not kill all of the bacteria. The bacteria that an antibiotic does not kill can grow stronger.” What is right and what is wrong with this statement? Briefly explain, and provide a revised statement that portrays the evolution of antibiotic resistance more accurately and effectively (5 points). Exam continues on next page https://www.drugs.com/cg/antibiotic-resistant-bacteria.html Page 4 4. In many species of beetles (for example, the forked fungus beetle Bolitotherus cornutus shown at right), males have horn-like protuberances on their heads that are absent in females. A. Could horns in male forked fungus beetles be an example of a trait that has evolved by intrasexual selection? Briefly explain how intrasexual selection could have led to the evolution of horns, and briefly explain how you could test this hypothesis (2 points). B. Could horns in male forked fungus beetles be an example of a trait that has evolved by intersexual selection? Briefly explain how intersexual selection could have led to the evolution of horns, and briefly explain how you could test this hypothesis (2 points). C. In the population of forked fungus beetles around Meadville, you find continuous variation in male horn length; most males in the population have average-length horns, but some have horns that are considerably longer or shorter than average. Briefly describe the two ways you could determine if this variation in male horn length has a heritable genetic basis (2 points). 5. The three-spined stickleback is a species of fish in which males in breeding condition have bright red bellies. Laboratory and field experiments have shown that females strongly prefer to mate with males with the very reddest bellies. Would you therefore be justified in concluding that males of future generations of sticklebacks will have bellies that are even redder than those of present-day males? Briefly explain why or why not (4 points). Exam continues on next page Page 5 6. Imagine that you are studying the sky pilot Polemonium viscosum, a small insect-pollinated alpine plant of the southern Rocky Mountains. About 15,000 years ago during the last ice age, this species existed in one continuously distributed population at lower elevations on the slopes of Mt. French and Mt. Venesky, two of the more imposing peaks of the southern Rockies. As the earth has warmed over the last 15,000 years, however, the elevational range of the species has shifted upward; now sky pilots exist only in two isolated and genetically distinct populations at the summits of the two mountains. The shaded regions in the figure at right reflect the past and current distribution of the species. A. What two evolutionary processes are most likely to be responsible for the genetic differences that now exist between the Mt. French and Mt. Venesky population of sky pilots? Briefly explain (2 points). B. Could the sky pilot populations on Mt. French and Mt. Venesky eventually evolve into two separate sky pilot species? Briefly explain (1) what conditions would be necessary for speciation to occur, and (2) what type of speciation process is most relevant to this situation (3 points). C. On Mt. French, sky pilots are very common and the population size is currently very large (>10,000 plants). On Mt. Venesky, however, sky pilots are quite rare, and the total population is currently fewer than 500 plants. Based on this information, which of the two populations of sky pilots is likely to be genetically most different from the "ancestral" population of sky pilots that was continuously distributed around the two mountains 15,000 years ago? Briefly explain (2 points). D. Now fast-forward 15,000 years — after the coming zombie apocalypse, attack of the murder hornets, and rule of the Night King — to a future post-apocalyptic ice age. Imagine that cooling of the earth’s climate and glaciation at higher elevations creates conditions that allow the two sky pilot populations to spread down from their respective mountain tops and rejoin on the slopes beneath the two peaks (see shaded regions in the figure at right). Using the Biological Species Concept as your guide, how could you determine whether the Mt. French sky pilot and Mt. Venesky sky pilot should be recognized as two distinct species? Briefly explain how you could make this assessment (3 points). Congratulations! You are done! Best wishes for the holidays and the New Year!