Project #211724 - biology

Science Tutors

Subject Science
Due By (Pacific Time) 11/13/2017 11:00 pm

Please read the Module Six Discussion Board Reading linked here: skin_pigmentation.pdfView in a new window.

As you read about the evolution of skin color, think about the questions within the article and then post here on some of the following questions. Note** each person doesn’t not have to answer every question but you should each be writing at least a paragraph per post. Remember to post twice before the due date (once as your own post and once as a response OR twice in response to other people’s posts). This is a long one so you can pick and choose which sections you want to comment on. Here are some questions to think about to help get the discussion going:

  1. What are the causes of skin cancer and why are Caucasians more at risk of skin cancer than other populations?
  2. Based on the amount of UV light reaching the Earth what latitude receives the greatest amount of UV light? The least? So where where might you expect to find the most lightly pigmented and most darkly pigmented people on the planet? Why?
  3. Some populations have skin colors that are darker or lighter than predicted based on their location (their data point falls somewhere outside of the line shown in Figure 2). What might explain the skin color of these exceptional populations? Propose a few hypotheses.
  4. How is folate linked to natural selection? All other things being equal, which skin tone would you expect to be correlated with higher levels of folate?
  5. How is vitamin D linked to natural selection? Which skin tone allows someone to maintain the recommended level of vitamin D? 
  6. Taking vitamin D and folate into consideration, what would happen to the reproductive success of:
    • A light-skinned person living in the tropics?
    • A light-skinned person living in the polar region?
    • A dark-skinned person living in the tropics?
    • A dark-skinned person living in the polar region?
  7. Are UV light, vitamin D and folate needs sufficient to explain the current world distribution of skin color?
  8. How might you explain that Inuits, living at northern latitudes, are relatively dark-skinned (much more so than expected for their latitude)? Propose a hypothesis.
  9. Think of the forces that affected the evolution of skin color in the past. Contrast these to the factors that affect skin pigmentation today. Hypothesize about the factors that may affect skin pigmentation in the future.
    • Do you think the impact of natural selection on skin color is as strong today as it was in the past?
    • What factors may have decreased or increased selection today? 
    • Predict skin color distribution in the year 2500. Outline your assumptions and the reasons for your predictions. 


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