High levels of solar radiation

Unquestionably the environmental stress of high levels of solar radiation negatively effects survival humans.Exposure to sunlight can be very harmful to the skin and many people forget or ignore that the sun is one of the most powerful sources of energy in nature. solar radiation have a negative effect on health because one can develop various types of skin cancer. The dark skin help to protect from high solar radiation because dark skin contains a lot melanin so that little solar radiation can penetrate the skin. In other hand, people who have a lighter skin color can easily get sun burns and skin cancer. However, it doe not matter if one has dark or light skin, everyone can be affect by high levels of solar radiation.

2 Identify 4 ways in which humans have adapted to this stress.

a) Short-term adaptation: sunscreen helps to respond quickly to changes of high levels of solar radiation because little solar radiation can penetrate the skin. Sunscreen protects people for a short time, and it is easy to wash off. (I could not find a good answer for this one because sunscreen is a tool of protection)

b) Facultative adaptation: When there is less solar radiation like in winter, skin ability to tan are higher due to the increase in of the melanin granules. this change is much longer than Short-term adaptation

c) Developmental adaptation: humans can adapt over the time to high levels of solar radiation. We can develop more melanin. What is melanin?? Melanin is a dark pigment and filter of defense to solar radiation. It radiation is reflected out and prevented from entering the body. Therefore, melanin is mainly to protect the same skin from sunlight.

d) Cultural adaptation: humans have adapted very well to high levels of sol radiations because we have been developed many tool to protect us from the sun. for example, we created clothing, houses, sunscreen, umbrellas, etc.


3- study human variation in different environmental climes is very beneficial for many reasons. We can understand the causes of many diseases; consequently we know how to prevent them. Studying the high levels of solar radiation we can find the answer of why skin pigmentation is different in places in the world.


4- By studying levels of sol radiation, one can understand the diversity of skin tone among humans. The first actual humans arose in Africa between 120,000 and 100,000 years. They had a dark skin to protect from the solar radiation and high temperatures of the Ecuador. Dark skin contains a lot melanin so that little solar radiation can penetrate the skin. The exposure to sunlight incites the production of vitamin D (It increases absorption of calcium and phosphorus). When humans began to migrate out of the tropics and become established in places where they receive a much lower solar radiation their excessive natural protection against the sun was harmful. The travelers who migrated out from Africa to regions more to the south and north had a big problem developing vitamin D, so it could causes diseases like rickets and another problems related with the calcium. In others words they could not absorbed very well the light of the sun, and produce the enough vitamin D because theirs skin contained too much eumelanin. The only solution was to lose some skin pigmentation. When they began to adapt to in their new environment the melanin changed, and consequently they got a skin color lighter to survive.