PartVI-Vitamin D:Still Another Way of Looking at It Folate can explain why dark
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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
20) A person need just the adequate amount of UV light as humans require UV light forVitamin D. More exposure equals more pigment for the perfect balance. Vitamin D is used maintain a healthy heart ,stable nervous system and an effective immune system .
21) It depends on your geographic setting as there are areas that require more or less
pigment to balance out the folate content.maintain a recommended level of vitamin D would be a darker skin .This is because lighter skin allows deeper penetration by UV rays.
22)
Humans require an adequate amount of UV light to produce Vitamin D but not excessiveto harm the DNA in the body. This is done by the amount of pigment in the skin tobalance out the Vitamin D production and The evolution of the variation and distribution of human skin color depends on where you live . Pepole close to the equator will have darker skin .It varies in different places around the world people moved to further areas from the equator with lower uv levels ,allowed UV rays to penetrate the skin and produse more vitamin D.
23)
a.There is a lot of Vitamin D production if folate is not an issue, easy
b. If there is enough Vitamin D production go ahead, but there may not be enough
light to produce vitamin D
c.There is enough pigment to balance out the sunlight needed
d.There is too much pigment for the area so there would be insufficient Vitamin D
24) Taking vitamin only vitamin D into consideration , I think that skin tones near the equtor would be medium, skin tones near the north would be very dark, skin tones near the south wold be very dark , skin tones between the north and equator would be light and skin tones between the south and equator would be light.
25) It can't explaine the distribution because the UV rays only help the body to utilize the Vitamin D.