PartVI-Vitamin D:Still Another Way of Looking at It Folate can explain why dark
ID: 143614 • Letter: P
Question
PartVI-Vitamin D:Still Another Way of Looking at It Folate can explain why dark skin evolved, but it cannot account for the evolution of light skin. Another factor must be at play. Vitamin D, is essential for normal growth, calcium absorption, and skeletal development. It is particularly important in maintaining and repairing healthy bones and teeth. Its role in calcium absorption makes it essential in maintaining a healthy heart, blood clotting, a stable nervous system, and an effective immune system. Deficiencies manifest themselves as rickets (softening of the bones), osteoporosis, and osteomalacia. It can lead to death, immobilization, or deformities. Women have a higher need for this nutrient during pregnancy and lactation due to their need to absorb calcium to build the fetal skeleton. Humans can obtain vitamin D, by one of two means. They can consume it in certain foods (fish liver oil and, to a lesser extent, egg yolk are good sources). Alternatively, skin cells have the ability to synthesize it from a cholesterol-like precursor. However, is process requires the energy of UV radiation. Theoretical research on the dose of ultraviolet radiation required to produce vitamin D, suggests that for moderately to darkly pigmented individuals (Figure 5) There is enough sunlight reaching the tropics (approximately 5 north of the Tropic of Cancer to approximately 5° south of the Tropic of Capricorn) to meet all of a human's requirement for vitamin D throughout all months of the year. This is indicated by the dotted area on the map. Note: Vitamin D, is not produced to toxic levels when high quantities of sunlight are present. In the area indicated by narrowly-spaced obliques, there is not enough ultraviolet light to synthesize vitamin D, in human skin for at least 1 month of the year In the area indicated by widely-spaced obliques, there is mot enough UV light for the skin to synthesize vitamin D, in any month of the year Figure S. Amount of UV light available to synthesize recommended levels of vitamin D for a moderately to darkly pigmented person at various locations around the world. Sowree: reprinted from The Journal of Haman Fivl 31). Jablonski, N.G. and G. Chaplin, The Evolution of human skin coloration. pp. 57-106 Figure 2 copyright (2000), with permission fromExplanation / Answer
Answer 26- Towards the poles the skin tone would be lighter since the U.V light is not as strong and a fair skin is needed to take in the necessary amount of Vitamin D. Whereas toward the equator, the darker skin tone s more necessary as there is more than enough sunlight to give a person a recommended dose of Vit. D
Answer 28- Inuits could be more darker skinned than expected due to the long summer days where the sun stays out all summer.
Answer 29- May be sun overcast could be blocking the U.V light from making direct contact with the land
Answer 27- we believe so