Question

1. Background information regarding what skin pigmentation is and/or why humans have skin pigmentation
2. Why dark pigmentation is an adaptation to the selective pressure(s) found near the equator
3. Why light pigmentation is an adaptation to the selective pressure(s) found at higher latitudes

Please give a thorough and detailed answer to these three questions, thank you.

Answer 1

◆ melanin is called as skin pigment .

◆ melanocytes produces pigment melanin by specialized group of cells .

◆ melanin cause the skin to darken when expose to UV radiation by the process of melanogenisis .

◆ it dissipate over 99.9% of absorbed UV radiation by melanin pigment.

◆ human have skin pigment to protect the skin from UV rays.

◆ Increasing melanin may also prevent the body from skin cancer .

◆ dark pigmentation is adapted near the equator because :-

• Strong sun exposure damage the body and cause skin cancer , so dark skin prevent the body from UV B radiation .
• Darker skin at equator helps in preventing folate deficiency.
• Melanocyes are found in basal layer of epidermis .
• Melanin hinder vitamin D synthesis so it cause rickets in childrens with poor nourishment .
• To to high radiation exposure human body adapted to that environment by increasing number of sweat gland and reduce amount of body hair to maintain body temperature (cool).

◆ light pigmentation is​  adapted to the higher latitudes because :-

• Light pigmentation at higher latitudes due to low UV radiation exposure
• Due to minimum exposure of UV light , low melanin (eumelanin) production .
• Eumelanin pigment are adapted to low radiation exposure so it allow the UV radiation to penetrate the skin and produce vitamin D .
• Lighter skin absorb UV radiation ( qualitatively ) and synthesized higher amount of vitamin D .
• Increase exposure of lighter skin to radiation near the equator cause higher risk of cancer i.e. skin cancer .

• Albinism is a rare disorder it is due to low level of melanin .