2. Reactions to cold weather and extreme low temperatures can be seen through developmental adaptions and short term responses. Developmental adaptions are actual changes in the DNA of a population of individuals in response to a long-term stress (in this case, cold temperatures) to produce a phenotypic change through evolutionary forces. The population changes over generations.
- Heat Retention: More efficient than heat production because it requires less energy. Energy is obtained from dietary sources and unless food is abundant, any factor that conserves energy can be beneficial.
- Metabolic Rate Increase & Shivering: Increases in metabolic rate and shivering are short-term responses that generate body heat. Increases in metabolic rate (the rate at which cells break up nutrients) release energy in the form of heat. Shivering also generates muscle heat, as does voluntary exercise. As mentioned before, these actions pose a threat because large amounts of nutrients are required to provide more energy to complete these actions.
- Vasoconstriction: Another short-term response to extreme cold temperatures. Instead of producing heat like the previous mechanisms, it minimizes heat loss and therefore is more energy efficient. Vasoconstriction differs from vasodilation (used in extreme heat) as it restricts capillary blood flow to the surface of the skin, thus reducing heat loss at the body surface. Creating body heat is more economical than creating it, therefore vasoconstriction is very efficient in above freezing temperatures. However, if temperatures drop to below freezing levels, vasoconstriction can serve as a negative response which will ultimately lower the skin temperature to the point of frostbite or potentially worse.
- Weight & Height: In general, people exposed to chronic cold (the majority of the year) maintain higher metabolic rates than people who live in warmer climates. Diets that consist of high animal protein and fat diet serve to maintain high metabolic rates required by exposure to chronic cold. In general, the body shape tendency of populations living in cold climates is to be squat and round, allowing individuals to retain more heat in their body core.
3. There are many benefits of studying human variation from the perspective across environmental clines rather than basing it off of race. Through the use of clines, we are able to see how different races and species adapted to certain environmental stresses. A benefit to using information from explorations like this is that we can see natural selection in action. This information can be used in a productive way by helping us learn about learn more about the human species and how exactly they react and adapt to these stresses (heat, cold, high altitude, etc.)
4. In Biology, the term race refers to geographically pattern phenotypic variation within a species. Up until the twenty-first century, race was used to express human variation of environmental stresses, but now scientists study human variation over environmental clines. I can use race to understand the variation of the adaptations listed in #2 because certain races have specific habits and rituals, such as their diet and eating patterns (bullet 4; #2).
The study of environmental influences on adaptions is a better way to understand human variation than by the use of race because there is major limitation of traditional classification by means of race. These traditional ways are inherently typological thus categorizing things based on stereotypes or ideals that comprise a specific set of traits. These beliefs and typologies are often incorrect because any grouping made will always include some individuals that do not conform to every single aspects of a particular race.
