Lab 2 Evolution I

Lab 2: Evolution I 1. How would biologists explain how the mice on the lava flow evolved black fur? Include all the elements you think are needed for a full explanation. (1) Biologists explain how the mice on the lava flow evolved black fur through evolution by natur selection. The elements that helped this process were variation, inheritance, differences in survival/reproduction, and adaptation. There was variation in whether or not the mice had the dark hair trait, the inheritance of this trait was passed down from their parents, more mice had dark fur due to the terrain (it was easier to blend in), and they adapted over a period of time so that the majority of the population had dark fur. 2. Would biologists say that the mice changed because they wanted or needed to change? Why or why not? (1) Biologist would say that the mice needed to change because the change in the terrain caused them to be more vulnerable to predators, so it the mice were going to survive the majority to the population needed to have the dark fur allele. 3 - 6 Review the questions below before watching the remainder of the film. Record evidence you see or hear in the film that supports each condition for natural selection for the change in fur color in some rock pocket mouse populations. (1 each) Condition 3. Variation Description A population of a specific species that have contrasting traits. Evidence - There are light and dark colored mice. This is when a trait gets passed down to an offspring from its parents. - 5. Differential survival and reproduction The offspring with the more favorable traits of a certain condition is more likely to survive and reproduce. - 6. Adaptation A specific trait will become more apparent throughout generations in order to survive certain conditions. - 4. Inheritance - - - Dark colored mice inherit that trait from their parents. Light colored mice inherit that trait from thei parents. Predators prey on the mice that stands out the most. The light-colored mice thrive in the desert, but stick out on the dark lava terrain Over time the dark colored mice took over most of the population because this species had to adapt to the dark lava terrain It only took 1000 years for the population to be 95% dark colored mice. 7. Calculate the percentage of tan mice in each population from the data in Table 1. And enter your calculations in the last row in Table 1. (2) Table 1. Percentage of tan mice in different populations. This is the same data as shown in Figure 1. Population Soil color Number of tan mice Number of dark mice Total number of mice (tan and dark) Percentage of tan mice Christmas Pass Light 6 Tule Well Lava (West) Lava (Mid) Lava (East) Light 80 Dark 0 Dark 0 Dark 3 O’Neill Pass Light 34 0 5 7 5 42 43 6 85 7 5 45 77 100% 94% 0% 0% 7% 44% 8. Which populations show evidence for variation in fur color? Add the evidence to your Evolution by Natural Selection Explanation Table as needed. (1) The populations that show evidence for variation in fur color are the Tule Well, Lava East, and O’Neill Pass populations. All of these have both tan and dark mice, as shown in Table one. 9. Describe how the evidence you collected relates to one or more of the major principles of natural selection. (1) The evidence relates to variation and differential survival and reproduction because the color of a mouse’s fur will have an impact on whether it will survive. Due to some environments like the dark lava terrain, the variance will become less because mice with darker fur are more likely to survive. 10. What pattern or patterns do you see on the graph in Figure 2? (1) The color of a mouse’s fur is determined by the alleles for the MC1R gene, so the lightest fur would be from two copies of allele one, the darkest fur would be from two copies of allele two, and heterozygous mice have copy of each allele. 11. Make a claim about whether differences in fur color are inherited. Support your claim with evidence from Figure 2. Add the evidence to your Evolution by Natural Selection Explanation Table as needed. Also, describe how the evidence relates to the major conditions of evolution by natural selection. (1) In figure two, it is shown that the genes passed down from their parents determine fur color. This proves that fur color can be an inherited trait. 12. Make a claim about whether the frequencies of alleles that affect fur color are different in populations on light or dark backgrounds. Support your claim with evidence from Figure 3. (1) Frequencies of dark colored fur alleles are higher in populations on dark backgrounds, and frequencies of lig colored fur alleles are higher in populations on light backgrounds. This is proven in figure three because the frequency in allele two are high in all the lava territories, which are also dark backgrounds. 13. Calculate a. The overall frequencies of light-colored mice and dark-colored mice caught on light-colored substrates. frequency = number of mice of one color/total number of mice (1) Frequency of light colored mice = 120/168 = 71% Frequency of dark colored mice = 48/168 = 29% b. The overall frequencies of light-colored mice and dark-colored mice caught on dark-colored substrates. frequency = number of mice of one color/total number of mice (1) Frequency of light colored mice = 3/57 = 5% Frequency of dark colored mice = 54/57 = 95% 14. Using the Hardy-Weinberg equation and data from the table above, a. determine the number of mice with the DD and Ddgenotypes on the light, rocky, granite substrate. (1) dd genotype = 71% DD genotype = 3% Dd genotype = 26% b. the number of mice with the DD and Dd genotypes on the darky, rocky lava substrate. (1) dd genotype = 5% DD genotype = 61% Dd genotype = 34% 15. Which fur color seems to have the greatest overall selective advantage? Use data collected from both dark-colored and light- colored substrates to support your answer. (1) The dark fur seems to have the greatest overall selective advantage because the percentage of dark furred mice is higher (29%) in light backgrounds than light furred mice in dark backgrounds (5%). 16. In a separate study, 76 rock pocket mice were collected from four different, widely separated areas of dark lava rock. One collecting site was in Arizona. The other three were in New Mexico. Dr. Nachman and colleagues observed no significant differences in the color of the rocks in the four locations sampled. However, the dark-colored mice from the three New Mexico locations were slightly darker than the darkcolored mice from the Arizona population. The entire Mc1r gene was sequenced in all 76 of the mice collected. The mutations responsible for the dark fur color in the Arizona mice were absent from the three different populations of New Mexico mice. No Mc1r mutations were associated with dark fur color in the New Mexico populations. These findings suggest that adaptive dark coloration has occurred at least twice in the rock pocket mouse and that these similar phenotypic changes have different genetic bases. How does this study support the concept that natural selection is not random? (1) This proves that what the mice are experiencing is common and similar adaptations occur in similar environments. 17. a. The MC1R protein in the dark rock pocket mouse population from the Pinacate lava flow contains how many mutations? (1) It has four mutations. b. Compare the amino acid data of dark-colored mice from the other three populations to that of the wildtype (light colored) mice in the Pinacate region. What do you notice? (1) The other three populations in the Pinacate region have normal MC1R receptor protein and the dark colored fur phenotype. c. Use the information in the excerpt below to explain the evolutionary significance of MC1R protein variations in the different mouse populations. (3) This excerpt explains that dark colored mice have evolved through adaptations of certain genes. The gene tha adapted increased the production of pigment melanin. This just further proves that evolution is not just some random process, and it can occur in similar was if the conditions are similar. Post Lab Questions (2 points each) 1. Oldfield mice (Peromyscus polionotus, also called beach mice) in the southeastern United States belong to a different genus than rock pocket mice (Chaetodipus intermedius). Oldfield mice from the mainland live in areas with dark soils. These mice mostly have dark fur. Populations of the same species that live on the white beaches of Florida and Alabama have light fur. Describe the evidence you would need to collect to support the claim that the differences in color in these populations are due to natural selection. The first bit of evidence that needed to be collected would be variation in dark fur and light fur for a specific population. Then the inheritance would need to be tested by recording the color of fur of offspring in relation to their parents while keeping conditions the same. Next it would need to be proven that light colored mice d better in light backgrounds and dark colored mice do better in dark backgrounds. This can be shown by recording the ratio of each colored mice in the environments. Lastly, there would need to be evidence that proved that the frequency of mice with the light fur allele makes up most of the population on the white beaches and that the frequency of mice with the dark fur allele makes up most of the population on the dark soils. 2. Describe the types of evidence you would need to collect to support the claim that differences in skin color among humans are the result of natural selection. The first bit of evidence that would need to be collected would be the variation in skin color for a specifi population. Then the inheritance would need to be tested by looking at offspring’s parents to prove that that trait can be passed down. Next it would need to be tested that people with darker complexion survive in certain environments better than people with a light complexion and vice versa. Lastly, the frequency o people with the dark skin alleles makes up most of the population where the environment makes it easier for people of a darker complexion to survive and vice versa. 3. Humans also have an MC1R gene, and scientists have discovered that it’s one of the genes that determines the type and amount of melanin in a person’s skin. If you wanted to study whether skin color, like mouse fur color, has evolved by natural selection, what additional challenges do you imagine in collecting data or designing experiments to explore skin color evolution in humans? Make a list of at least three additional challenges One challenge is that the numbers that are on record today most likely do not correlate with history due to things like slavery and discrimination. Another challenge is that humans are at the top of the food chain, so blending into an environment is not as important as it is for the mice. The last challenge is humans have a lot more time in a generation than mice do.