1. Solar radiation can negatively
impact the survival of humans by disturbing homeostasis especially if solar
radiation is high. Let’s look more closely at the Sun; it emits short-wave ultraviolet
radiation (UVR) that is potentially harmful to life. It therefore can be said UVR is a force of
evolution whereas humans had to adapt to the environmental stress of UV
radiation or perish. For example, as overexposure
to solar or UVR it causes skin cells to mutate creating cancer cells and
therefore cancer. Aside from cancer, if
high levels of UV radiation are exposed to a person’s skin it causes a breakdown
of B vitamin, a folate. Women, men, and children are all sensitive to folate
levels and as such it can cause all different side effects. For women who are
pregnant they are prescribed vitamins with enough folic acid to decrease the risk
of miscarriages and prevent defect in babies such as neural tube defects. Earlier
in their stages of pregnancy, folate is an essential vitamin for the process of
DNA replication. For men, a lack of
folate can result in a reduction in the production of sperm cells. Lastly, increased
sunlight exposure increases the chance for children to develop multiple
sclerosis. Looking at skin color, light-colored skin favors production of
vitamin D in northern latitudes, whereas darker colored skin can prevent people
from producing enough vitamin D (necessary for Ca absorption)resulting in
rickets disease in kids and osteoporosis in adults.
*Darker skin more prone to frostbite than lighter skin
2.
A. Short Term
Unfortunately, there isn't a short term adaptation to solar
radiation making it a dangerous stress especially for individuals with low levels
of melanin.
B. facultative adaptation
An example of a facultative adaptation is tanning. The
physiological response to this environmental stress is influenced to an extent
by duration and severity of the exposure. The simplest form of accommodation is
tanning; it is a quick and temporary response due to external environmental
changes. As an example, increased
exposure results in tanning and a decrease in exposure over time the skin will
revert to its original color. Simply put, by increasing the number of melanin
granules and the percent of different variations of melanin is responsible for
a tan.
C. developmental adaptation
Melanin can have protective qualities against the harmful
effects of solar radiation which is a developmental adaption. So what determines skin color is the next
question, the answer would be the number and size of melanin particles. For instance, an individual with a higher ratio
of pheomelanin their skin will tend to be more red to yellow color based.
Individuals who have a higher percentage of eumelanin their overall
hue will be more dark brown to black tint.
Studying human variation in this manner is beneficial
because it expresses environmental stresses and teaches us how various populations
adapt to them. This information can be used to understand why fair skinned
races are more susceptible to skin cancer then dark skinned races. It also
helped in the development of sunscreen lotion which is an artificial version of
melanin. Races that express the trait
for dark complexion are genetically favored by natural selection when it comes
to solar radiation.
D. Cultural adaptation
Solar radiation is so damaging that our body can’t react
fast enough other than physically seeking shelter when the sun is out when
there is nowhere to go for shade. Adaptations
such as wearing hats etc. are more behavioral than any other type of
adaption. Examples of cultural
adaptations are sunglasses, hats, clothes and sunscreen. Before people spend a day in the sun, they
will usually apply sunscreen to prevent or reduce risk of skin damage and
tanning. People also wear sunglasses,
hats and extra clothing (beach cover-up) to protect them from solar radiation.
3. The study of the gradual change
of a species' traits across different populations is beneficial because it shows
why certain people have health problems, or are healthier than others or have
the skin tone they do, or why it is beneficial to have the skin tone that they
do. By looking at the clines of solar radiation (where melanin is protective
against UV) versus the need for vitamin D absorption (where melanin is not
protective against UV) shows that in areas where UV protection is needed, skin
color is darker, and where people need more vitamin D over UV protection, their
skin is lighter. By using UV radiation as a factor in studies high frequencies
of rickets disease, or the need for vitamin D in healthy pregnancies, it can be
helpful to know who needs more vitamin D, or need to be in the sun less or more
to be healthier.
4. The study of environmental influences on
adaptations is a better way to understand human variation than by the use of
race because race is a cultural and social characteristic. The adaptations of solar radiation are better
understood by studying the 4 facets of adaptation (short term, facultative, developmental
and cultural). As seen in the
developmental adaptation melanin, skin color is the result of this adaptation.
Different environmental clines and melanin makeup in individuals are what cause
skin color. It is one of the many adaptations to deal with high levels of solar
radiation. These adaptations are key to these major variations and changes in
the appearance and makeup of humans. Environmental influences are what must be
studied in order to learn about why there is variation among humans, especially
skin color. The variation of skin color
shows that our bodies are influenced by many simple things that normally people
would not think of like the sun or altitude. Race on the other hand is all
cultural based and has little to nothing to do with skin color at all therefore
it is easier to understand variation by looking how a population adapts to
exposure of the sun by the pigmentation of the skin.
