University:
Eastern Kentucky University
Course:
BIO 112 | Ecology and Evolution
Academic year:

2022
Views:

388

Pages:

3
Author:

ilikemyicons0y5

1. [0.5pt] Describe the relationship between the UV Index (the colored bar in Figure 1) and latitude (y-axis). As the latitude gets farther away from the equator north and south, the UV Index gets weaker. 2. [0.5pt] How do you explain the relationship between the UV Index and latitude? (In other words, why does UV intensity change with latitude?) The UV index changes with latitude because the angle of the sun hits the earth diﬀerently. At the equator, the sunlight has a direct path while further away, the sunlight hits the earth at an angle. 3. [0.5pt] Find your approximate location on the map. What is the primary UV Index value of your state on this particular day in September? The primary UV index of Colorado is 8 5. [0.5pt] In the ﬁlm, Dr. Jablonski explains that melanin, located in the top layer of human skin, absorbs UV radiation, protecting cells from the damaging eﬀects of UV. Genetics determines the type of melanin (i.e., brown/black eumelanin or red/brown pheomelanin) and the amount of melanin present in an individual’s cells. Based on this information, write a hypothesis for where in the world you would expect to ﬁnd human populations with darker or lighter skin pigmentation (i.e., diﬀerent amounts of melanin). People with darker skin pigmentation probably live around the equator because there is stronger UV radiation in that area, so their skin would need a greater protection. Lighter skin pigmentation would be found in lighter variations as they move to greater latitudes because there is less UV light. 6. [0.5pt] Explain how scientists could test the hypothesis you developed above. Scientists could test how much melanin people have who are native of diﬀerent areas around the world. If people who live near the equator have more melanin while people who live in higher latitudes have less melanin, then the hypothesis is correct. 7. [0.5pt] Why do you think that reﬂectance data are collected from a subject’s inner arm? The inner arm doesn’t see as much sun and is usually lighter than the rest of the body, so measuring here would have less interference from daily sun. 8. [0.5pt] Describe the relationship between skin reﬂectance (y-axis) and latitude (x-axis). Consider both the direction and steepness of the lines’ slopes. While going south latitudinally, there is a positive relationship between latitude and skin reﬂectiveness. While going north latitudinally, there is a steeper positive relationship between skin reﬂectance levels and latitude. 9. [0.5pt] Do these data support your hypothesis from Question 5? Explain your answer with speciﬁc evidence/details. It semi-supports my hypothesis. People with darker skin color do live closer to the equator but the the same place latitudinally north and south do not have the same skin reﬂectance, as seen by ﬁgure 2. 10. [1pt] Based on what you know about skin pigmentation so far, suggest a mechanism by which UV intensity could provide a selective pressure on the evolution of human skin color. Describe this mechanism using words and a ﬂowchart/diagram.

UV Index and Skin Color

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