1. Select only ONE of
the following environmental stresses: (a) heat, (b) high levels of solar
radiation, (c) cold, or (d) high altitude. Discuss specifically how this
environmental stress negatively impacts the survival of humans by disturbing homeostasis.
The disruption of homeostasis can occur with high levels of
solar radiation which is an environmental stressor. The reason High levels of
solar radiation negatively impact the survival of humans is due to the fact
that while UVB radiation penetrates through the epidermis layer, UVA radiation
has the ability to go beyond the epidermis and penetrate straight through to
the dermis layer. Although UV radiation does provide stimulation of vitamin D
production through UVB waves which is beneficial to humans, overexposure of UVB
and UVA rays can still cause dangerous sunburns and short-term suppression of
immune systems. This type of UVB exposure becomes directly absorbed by the DNA
within cells, and this absorption has the dangerous potential to cause genetic
damage that could lead to skin cancer. Any genetic level damage directly
disturbs homeostasis and is potentially life threatening to humans.
2. Identify 4 ways in
which humans have adapted to this stress, choosing one specific adaptation from
each of the different types of adaptations listed above
SHORT TERM: Humans
have adapted to exposure to the sun in appropriate and measured timeframes that
are unrelated to vitamin D production. Short term adaptations consist of enhancing
mood and energy through the release of endorphins, melatonin regulation through
the "third eye" of the pineal gland photoreceptors, regulating body
temperature, UV radiation also enhances skin barrier functions and helps in
treating skin diseases, such as psoriasis, vitiligo, atopic dermatitis, and
scleroderma.
FACULTATIVE: the process of developing facultative
pigmentation is better known as cosmetic tanning. Facultative Pigmentation is the
level of an acquired tan developed by an individual exposed to ultraviolet
light. It protects us from the harmful UVB radiation waves is skin
tanning. The process of tanning occurs
when exposure to sunlight activates a protective mechanism through increased
melanin production in the epidermis layer.
Melanin is our body’s naturally produced sunscreen and the degree of tanning
will take place until the overexposure to UV rays is reduced.
DEVELOPMENTAL: You
can see developmental changes in populations that have a higher concentration
of people with darker skin. Higher
concentrations of melanin are found in individuals with dark skin which acts as
a natural sunscreen that a person’s body produces. Populations that are more exposed to the
sun’s harmful rays reside in mostly in African and Tropical climates. In this regard, geographical locations makes
a difference in the number of people with darker skin however, those with
darker pigmentation can tan and sunburn as well. Regardless, of where one
lives, it is evident that too much exposure to solar radiation can result in
skin cancer and not enough exposure can result in a Vitamin D deficiency which results
in the inability to process calcium and also weakens bones. Populations that reside in locations with
limited sunlight can suffer adverse effects such as developing diseases like
rickets, which is when bones are too weak and can’t support the weight of the
body as it grows.
CULTURAL: Cultural
adaptations to protect a person’s body from harmful UVA /UVB rays has occurred through
clothing, adequate shelter and with the development of sunscreen. Clothing and
shelter gave humans the ability to protect themselves from direct exposure and
in turn resulted in the reduced levels of melanin production. Even by migrating
to environments that helped protect from harsh UVA/UVB elements such as
forested areas also helped to reduce sun exposure. Throughout history it is evident that skin
pigmentation has become lighter in various populations more specifically
northern geographical regions and darker skinned populations are more concentrated
in southern regions that are closest to
the equator.
3. What are the
benefits of studying human variation from this perspective across environmental
clines? Can information from explorations like this be useful to help us in any
way? Offer one example of how this information can be used in a productive way.
By studying the vicissitudes of diverse sample populations
over time, this enables us to assess and see how environmental stressors affect
various populations. One example would
be studying the high rate of sickle cell anemia in black populations. This type
of research can help scientists identify and develop treatments to hopefully
cure or just help other people diagnosed with sickle cell anemia and not just limit
it to one population. Also, studying the
cause and effect of rickets in populations with fair skinned people can help with
the understanding of the need for sunlight and how much of it is actually
necessary to avoid the certain diseases.
4. How would you use
race to understand the variation of the adaptations you listed in #2? Explain
why the study of environmental influences on adaptations is a better way to
understand human variation than by the use of race.
I believe that studying diverse races is an important aspect
of understanding variations of adaptations. I think race tells us quite a bit
and although it won’t answer all the questions, it would certainly give us
great insight. However, going by race alone would be rather myopic and would
have many limitations in regards to the information that we would be looking
for. Therefore, studying environmental influences of vast populations as a
whole would be more telling as to how outside stressors have influenced
adaptations in humans overall.
