The Evolution Of Human Skin Color 6n3b1q
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Vladlen Garder
5/19/2015
Period: 1
The Evolution of Human Skin Color 1. What are the causes of skin cancer? a. Over-exposure to the sun as UV rays are cancerous to humans. 2. Why are Caucasians more at ricks of skin cancer than other populations? a. There is less pigment in Caucasians where they can absorb more UV rays than any other skin color. 3. At what age does skin cancer typically occurs? Is the incidence of skin cancer greater in youth or old age? a. Around 65 years old b. The chance is greater in older humans 4. Does the amount of UV light reaching the Earth vary in a predictable manner? If so, describe the pattern you observe. a. Yes, The UV ray intensity is more intense near the equator and dissipates as you get further away from the equator 5. What latitude receives the greatest amount of UV light? The Least? 6. Based on these data, where might you expect to find the most lightly pigmented and the most darkly pigmented people on the planet? a. You would expect to see more pigmented skin near the equator, and further away from the equator you will see slightly less pigmented skin as you progress further away from the equator 7. Provide a rational to your answer above. a. There is more UV rays at the equator, which selects for humans with more pigment in skin. This results in more darker skin due to the amount of pigment produced 8. Interpret this graph and the trend it describes a. Is skin reflectance randomly distributed throughout the globe? If not, how would you describe the pattern? i. No, as white skin reflects UV rays more than darker colored skin. If you get further away from the equator, the lighter skin reflects more UV rays. b. Restate your findings in of skin color and UV lights i. Where there is more UV rays, the darker pigment absorbs more UV rays while the lighter colored skin reflects more UV rays c. How closely do these findings match the predictions of your hypothesis? i. Very accurately d. Some populations have skin colors that are darker or lighter than predicted based on the location. What might explain the skin color of these exceptional populations? i. A mass migration or population growth inside of a different population 9. Hypothesize why different skin colors have evolved. Based on what you know, what factor is most likely to exert a selective pressure on skin color? a. Different region of the globe have different UV light radiations where more UV light radiation requires more pigment in the skin to prevent keratin from denaturing. 10. Review your answer to Question 3. Keeping your answer in mind, how strong a selective pressure do you expect skin cancer to exert on reproductive success? a. Areas where there is more UV light radiation will require more Pigment in the skin. If there is not enough pigment where the UV light will begin to mutate the DNA. Then skin
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cancer will occur. That is why areas that require more pigment in the skin originated from the beginning. There is a very large selective pressure compared from someone from away from the equator vs someone on the equator. Based on this information, does your hypothesis about the evolution of skin color seem likely? Why or why not? How does skin color meet, or fail to meet, the three requirements of natural section outlined above? a. Yes, as geographically darker skinned people are near the equator and lighter skinned people are away from the equator. Based on Branda and Eaton’s results, what is the apparent effect of UV light exposure on blood folate levels? a. There is less folate in the patients compared to the normal exposure patients What is the apparent effect of UV light on folate levels in these test tubes a. There is less folate where there is extra UV radiation compared to the normal amount. How is folate linked to natural selection? a. The environment has situations that must be accustomed to live on, and the genes that favor the area more seem to be better on the area. The folate amount will be protected due to the amount of pigment in the area due to the selecting characteristic of the area. All other things being equal, which skin tone would you expect to be correlated with higher levels of folate? a. Darker skin tones Based on the new information, revise your hypothesis to explain the evolution of human skin color. a. Areas with more UV radiation to attempt to protect the folate levels must produce more pigment in the skin to protect the folate in the body system. What would happen to the reproductive success of: a. A light-skinned person living in the tropics? i. The person may encounter an insufficient folate amount and encounter skin cancer if enough pigment is not present b. A light-skinned person living in the polar region? i. The person will survive fine as there is less UV light radiation c. A dark-skinned person living in the tropics? i. The person will survive fine as there is enough pigment to combat the UV light radiation d. A dark-skinned person living in the polar region? i. The person may live just fine as there is not enough UV light to harm the person. But pregnancy requires a lot of folate and the sun provides Vitamin B production so there may be issues with carrying a child. Predict the skin tons expected at different latitudes, taking folate needs into consideration a. There will be darker skin tones at the equator and near the equator, but as you begin to move north or south of the equator there is less need for pigment so there will be lighter toned skin in those areas. Can folate explain the variation and distribution of light- and dark-skinned individuals around the world?
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a. A human requires the perfect amount of folate amount into the system and not too much sun light to reduce folate concentration and even damage the DNA How is vitamin D linked to natural selection? a. A person need just the adequate amount of UV light as humans require UV light for Vitamin D. More exposure equals more pigment for the perfect balance Which skin tone allows someone to maintain he recommended level of vitamin D? a. It depends on your geographic setting as there are areas that require more or less pigment to balance out the folate content Based on this new information, revise your hypothesis to explain the evolution of the variation and distribution of human skin color a. Humans require an adequate amount of UV light to produce Vitamin D but not excessive to harm the DNA in the body. This is done by the amount of pigment in the skin to balance out the Vitamin D production Taking only vitamin D into consideration, what would happen to the reproductive success of: a. A light-skinned person in the tropics i. There is a lot of Vitamin D production if folate is not an issue, easy b. A light-skinned person in the polar region i. If there is enough Vitamin D production go ahead, but there may not be enough light to produce Vitamin D c. A dark-skinned person in the tropics? i. There is enough pigment to balance out the sunlight needed d. A dark-skinned person living in the polar region? i. There is too much pigment for the area so there would be insufficient Vitamin D Predict the skin tones expected at different latitudes taking only vitamin D needs into consideration a. There would be darker skinned people near the equator, but lighter skinned people can live anywhere Can vitamin D alone explain the current world distribution of skin color? a. Lighter skinned people can live anywhere but darker skinned people would live closer to the equator so this wouldn’t really explain the reason much Using principles of natural selection, predict the skin tone expected at different latitudes, taking ultraviolet, exposure, vitamin D, and folate needs into consideration a. There will be more darker skinned people near the equator, and lighter skinned people further from the equator Are UV, light, vitamin D, and folate needs sufficient to explain the current world distribution of color? a. Yes How might you explain the Inuits, living at northern latitudes, are relatively dark-skinned? a. The group may have migrated as a group at one point in the group’s history Conversely, Northern Europeans are slightly lighter-skinned than expected for their latitude. Propose a hypothesis to explain this observation. a. The group may have migrated as a group at one point in history Which populations have insufficient amounts of vitamin D in their blood? a. East Asian and south Asian
Vladlen Garder
5/19/2015
Period: 1
31. What is common trait to all of these populations? How could this explain their deficiency? a. The area they live in have less UV light exposure and causes this problem 32. For several decades, milk and cereal have been fortified with vitamin D to help increase intake of this nutrient. Hypothesize why these fortification programs appear to be failing in some ethnic groups a. The group may find it unnecessary as the group already has enough vitamin d in the system to not require an artificial source of vitamin D 33. What should some Canadians do to avoid vitamin D deficiency? a. Move to an area with the proper exposure or artificially acquire the nutrient. 34. If individuals do not take steps to boost their vitamin D intake, hypothesize what might happen to their descendants in the future. a. The group may die off slowly as birth defects or self-health hazards may become an issue due to not enough vitamin D present 35. What might happen to Australians of European descent over time? a. The group may suffer from vitamin D deficiency or tan to acquire the pigment concentration depending on the differences in UV light concentration 36. 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. a. Do you think the impact of natural selection on skin color is as strong today as it was in the past? i. No b. What factors may have decreased or increased selection today? i. With access to vitamin d artificially or using sunscreen when needed c. Predict skin color distribution in the year 2500 i. Skin color will be spread out through the world as there is artificial ways to get vitamin d or protect yourselves from the sun. 37. During the trip, the lightly-pigmented individual is looking forward to lying on a beach ad working on his/her tan. Will this person be adapting to the environment? In other words, will evolution take place by developing a tan in a geographical region of intense UV light? a. Evolution as a group won’t occur but a temporary state change will occur as the person will acquire more pigment to conform to the situation 38. Should the lightly-pigment person wear sunscreen on the trip? a. Yes 39. Should this person wear sunscreen when he/she is at northern latitudes a. No, as the person needs more UV light and not repel the UV light.
5/19/2015
Period: 1
The Evolution of Human Skin Color 1. What are the causes of skin cancer? a. Over-exposure to the sun as UV rays are cancerous to humans. 2. Why are Caucasians more at ricks of skin cancer than other populations? a. There is less pigment in Caucasians where they can absorb more UV rays than any other skin color. 3. At what age does skin cancer typically occurs? Is the incidence of skin cancer greater in youth or old age? a. Around 65 years old b. The chance is greater in older humans 4. Does the amount of UV light reaching the Earth vary in a predictable manner? If so, describe the pattern you observe. a. Yes, The UV ray intensity is more intense near the equator and dissipates as you get further away from the equator 5. What latitude receives the greatest amount of UV light? The Least? 6. Based on these data, where might you expect to find the most lightly pigmented and the most darkly pigmented people on the planet? a. You would expect to see more pigmented skin near the equator, and further away from the equator you will see slightly less pigmented skin as you progress further away from the equator 7. Provide a rational to your answer above. a. There is more UV rays at the equator, which selects for humans with more pigment in skin. This results in more darker skin due to the amount of pigment produced 8. Interpret this graph and the trend it describes a. Is skin reflectance randomly distributed throughout the globe? If not, how would you describe the pattern? i. No, as white skin reflects UV rays more than darker colored skin. If you get further away from the equator, the lighter skin reflects more UV rays. b. Restate your findings in of skin color and UV lights i. Where there is more UV rays, the darker pigment absorbs more UV rays while the lighter colored skin reflects more UV rays c. How closely do these findings match the predictions of your hypothesis? i. Very accurately d. Some populations have skin colors that are darker or lighter than predicted based on the location. What might explain the skin color of these exceptional populations? i. A mass migration or population growth inside of a different population 9. Hypothesize why different skin colors have evolved. Based on what you know, what factor is most likely to exert a selective pressure on skin color? a. Different region of the globe have different UV light radiations where more UV light radiation requires more pigment in the skin to prevent keratin from denaturing. 10. Review your answer to Question 3. Keeping your answer in mind, how strong a selective pressure do you expect skin cancer to exert on reproductive success? a. Areas where there is more UV light radiation will require more Pigment in the skin. If there is not enough pigment where the UV light will begin to mutate the DNA. Then skin
Vladlen Garder
11.
12.
13. 14.
15.
16.
17.
18.
19.
5/19/2015
Period: 1
cancer will occur. That is why areas that require more pigment in the skin originated from the beginning. There is a very large selective pressure compared from someone from away from the equator vs someone on the equator. Based on this information, does your hypothesis about the evolution of skin color seem likely? Why or why not? How does skin color meet, or fail to meet, the three requirements of natural section outlined above? a. Yes, as geographically darker skinned people are near the equator and lighter skinned people are away from the equator. Based on Branda and Eaton’s results, what is the apparent effect of UV light exposure on blood folate levels? a. There is less folate in the patients compared to the normal exposure patients What is the apparent effect of UV light on folate levels in these test tubes a. There is less folate where there is extra UV radiation compared to the normal amount. How is folate linked to natural selection? a. The environment has situations that must be accustomed to live on, and the genes that favor the area more seem to be better on the area. The folate amount will be protected due to the amount of pigment in the area due to the selecting characteristic of the area. All other things being equal, which skin tone would you expect to be correlated with higher levels of folate? a. Darker skin tones Based on the new information, revise your hypothesis to explain the evolution of human skin color. a. Areas with more UV radiation to attempt to protect the folate levels must produce more pigment in the skin to protect the folate in the body system. What would happen to the reproductive success of: a. A light-skinned person living in the tropics? i. The person may encounter an insufficient folate amount and encounter skin cancer if enough pigment is not present b. A light-skinned person living in the polar region? i. The person will survive fine as there is less UV light radiation c. A dark-skinned person living in the tropics? i. The person will survive fine as there is enough pigment to combat the UV light radiation d. A dark-skinned person living in the polar region? i. The person may live just fine as there is not enough UV light to harm the person. But pregnancy requires a lot of folate and the sun provides Vitamin B production so there may be issues with carrying a child. Predict the skin tons expected at different latitudes, taking folate needs into consideration a. There will be darker skin tones at the equator and near the equator, but as you begin to move north or south of the equator there is less need for pigment so there will be lighter toned skin in those areas. Can folate explain the variation and distribution of light- and dark-skinned individuals around the world?
Vladlen Garder
20.
21.
22.
23.
24.
25.
26.
27.
28. 29.
30.
5/19/2015
Period: 1
a. A human requires the perfect amount of folate amount into the system and not too much sun light to reduce folate concentration and even damage the DNA How is vitamin D linked to natural selection? a. A person need just the adequate amount of UV light as humans require UV light for Vitamin D. More exposure equals more pigment for the perfect balance Which skin tone allows someone to maintain he recommended level of vitamin D? a. It depends on your geographic setting as there are areas that require more or less pigment to balance out the folate content Based on this new information, revise your hypothesis to explain the evolution of the variation and distribution of human skin color a. Humans require an adequate amount of UV light to produce Vitamin D but not excessive to harm the DNA in the body. This is done by the amount of pigment in the skin to balance out the Vitamin D production Taking only vitamin D into consideration, what would happen to the reproductive success of: a. A light-skinned person in the tropics i. There is a lot of Vitamin D production if folate is not an issue, easy b. A light-skinned person in the polar region i. If there is enough Vitamin D production go ahead, but there may not be enough light to produce Vitamin D c. A dark-skinned person in the tropics? i. There is enough pigment to balance out the sunlight needed d. A dark-skinned person living in the polar region? i. There is too much pigment for the area so there would be insufficient Vitamin D Predict the skin tones expected at different latitudes taking only vitamin D needs into consideration a. There would be darker skinned people near the equator, but lighter skinned people can live anywhere Can vitamin D alone explain the current world distribution of skin color? a. Lighter skinned people can live anywhere but darker skinned people would live closer to the equator so this wouldn’t really explain the reason much Using principles of natural selection, predict the skin tone expected at different latitudes, taking ultraviolet, exposure, vitamin D, and folate needs into consideration a. There will be more darker skinned people near the equator, and lighter skinned people further from the equator Are UV, light, vitamin D, and folate needs sufficient to explain the current world distribution of color? a. Yes How might you explain the Inuits, living at northern latitudes, are relatively dark-skinned? a. The group may have migrated as a group at one point in the group’s history Conversely, Northern Europeans are slightly lighter-skinned than expected for their latitude. Propose a hypothesis to explain this observation. a. The group may have migrated as a group at one point in history Which populations have insufficient amounts of vitamin D in their blood? a. East Asian and south Asian
Vladlen Garder
5/19/2015
Period: 1
31. What is common trait to all of these populations? How could this explain their deficiency? a. The area they live in have less UV light exposure and causes this problem 32. For several decades, milk and cereal have been fortified with vitamin D to help increase intake of this nutrient. Hypothesize why these fortification programs appear to be failing in some ethnic groups a. The group may find it unnecessary as the group already has enough vitamin d in the system to not require an artificial source of vitamin D 33. What should some Canadians do to avoid vitamin D deficiency? a. Move to an area with the proper exposure or artificially acquire the nutrient. 34. If individuals do not take steps to boost their vitamin D intake, hypothesize what might happen to their descendants in the future. a. The group may die off slowly as birth defects or self-health hazards may become an issue due to not enough vitamin D present 35. What might happen to Australians of European descent over time? a. The group may suffer from vitamin D deficiency or tan to acquire the pigment concentration depending on the differences in UV light concentration 36. 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. a. Do you think the impact of natural selection on skin color is as strong today as it was in the past? i. No b. What factors may have decreased or increased selection today? i. With access to vitamin d artificially or using sunscreen when needed c. Predict skin color distribution in the year 2500 i. Skin color will be spread out through the world as there is artificial ways to get vitamin d or protect yourselves from the sun. 37. During the trip, the lightly-pigmented individual is looking forward to lying on a beach ad working on his/her tan. Will this person be adapting to the environment? In other words, will evolution take place by developing a tan in a geographical region of intense UV light? a. Evolution as a group won’t occur but a temporary state change will occur as the person will acquire more pigment to conform to the situation 38. Should the lightly-pigment person wear sunscreen on the trip? a. Yes 39. Should this person wear sunscreen when he/she is at northern latitudes a. No, as the person needs more UV light and not repel the UV light.
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