High levels of solar radiation-
1. Normal exposure to ultraviolet radiation is important
because it is necessary in the creation of vitamin D. Without vitamin D, our
bodies are not as capable at absorbing calcium and phosphorus. Calcium is a
necessary component for building bones, maintaining heart health, blood
clotting, and used by the nervous system. Vitamin D is also helpful in fighting
infections.
However,
when exposure to solar radiation is too extreme, the melanocytes in the
epidermis responds by creating a larger quantity of melanin. Melanin acts a
filter, preventing the UV rays from acting as a mutating agent in the
individuals DNA. These mutations often lead to cancers, particularly melanoma,
and melanoma kills approximately 8000 Americans every year. Also, prolonged
exposure to UV radiation can also lead to anemia, due to folates breaking down
as a result of the radiation. Folates are also necessary in the process of
cellular reproduction, and the breakdown of these folates effects many cellular
process, particularly the production of sperm cells.
2. Short Term Adaptations- The melanocytes produce extra
melanin to filter out some of the UV rays when exposure levels are high. This
results in tanning of the skin.
Facultative Adaptations- The skin
will react to changes in radiation levels. If the radiation exposure is lower,
for example if a person moves to an area further from the equator (like moving
from Arizona to Alaska), or into an area with less direct radiation due to
environmental conditions (like Seattle, WA, which averages only 58 sunny days a
year) the body will not produce as much melanin. This works the opposite as
well, and the body will constantly fluctuate to adapt to the radiation in it
environment.
Developmental adaptation- Eventually,
humans adapt to their environments UV exposure by making some of the melanin
changes more permanent. In areas where radiation is higher, skin pigments tend
to be darker as a result of increases in overall melanin. In areas where the UV
radiation is lower, the benefits of lower melanin levels (resulting in more
vitamin D production, despite less UV radiation to create it) outweigh the need
for protection against the damage it causes.
Cultural Adaptations- Among the
many ways humans have culturally adapted to combat UV radiation, the two most
familiar are probably sunscreen and clothing. Sunscreen assists the natural
melanin process by filtering out a substantial quantity of the radiation before
it even touches the skin. Clothing choices, like head wraps worn by people in
the Middle East protects the skin by limiting
the amount of area that is exposed to the radiation in the first place.
- By looking at the effects of solar radiation, we can come up with new ways to either fight against the negative effects of too much radiation, or we can look for ways to improve the quality of life of those who don’t get enough. Improved awareness of the more dangerous effects of UV radiation, like skin cancers, can help those whose bodies are less able to filter the radiation (such as those with light skin). For those people whose bodies may filter too much radiation boosters of Vitamin D can greatly improve the quality of life, by combating anemia and increasing their ability to utilize more calcium.
- Human skin variation is a result of the exposure of the body to radiation over long periods of time. The darker skin tones are found closest to the equator where the solar radiation is the greatest, while lighter tones are found further from the poles, where the exposure to solar radiation is the lowest. It’s clear as you move up the latitudes (especially from sub-Saharan Africa up to Sweden), that melanin levels among indigenous peoples decreases.
1. Congo
2. Libya
3. Italy
4. Sweden
First of all, very good description of the stress itself and excellent images throughout.
ReplyDeleteRegarding your adaptations: All are correct, but for solar radiation, the question of short term adaptation is really a trick question. There IS no short term biological adaptation for solar radiation (other than a behavioral one of seeking cover), which is why this is such a dangerous stress for humans. No points deducted, I just like to see if students can figure this one out.
I like your discussion on the value of the adaptive approach. Your discussion on race kind of begs the question of whether race is a valuable approach to begin with. You say that skin color is not representative of a genetic difference between races... but can you really delineate a genetic line between races in the first place? That is the key to this question. Is race biologically useful to understanding human variation. You're on the right track but don't complete the thought.
Otherwise, well done.
This was a very interesting blog post! It is very interesting to read in-depth, about things which occur in our everyday life. I like the cultural adaptations you chose, sunscreen and head wraps. The use of clothing and head wraps was also a part of cultural adaptation in my blog post, but in regards to heat. Although they are very similar, it is interesting to see how many cultural adaptations co inside with one another. I also enjoyed your closing statement that skin color is simply an adaptation, not necessarily a way of defining someone.
ReplyDeletegreat post I enjoyed reading the whole post but your closing statement (like previously mentioned by MSAblogging13) was what stood out to me. Its strange that one thing like melanin in peoples skin would be what causes so many fights and disagreements. The levels of melanin shouldn't be what dictates social hierarchy , sadly enough this is what we see and sometimes unwillingly take part in.
ReplyDeleteThis post was great!I can tell you did your research on how the body absorbs sunlight and UV rays. I completely agree that we need to become more aware about the effects of too much UV exposure and do what we can to make others aware too. I also loved how you explained why different races were created. Its not that were different, we've all just adapted to our environments.
ReplyDelete