Clark Larsen Answers Students FAQs

1. Question: Why is “race” a social category rather than a biological one?

Response: “Races” are social categories that group humans according to any number and variety of physical traits. However, most of these traits, such as skin color, hair color, and eye color have continuous distributions. If, for example, all the different skin colors in the world were lined up from lightest to darkest, it would be difficult to draw lines between different colors. This is because there are no distinct categories for these biological traits. In essence, then, “race” categorization requires putting distinct groups on continuous variation. In reality, biological traits often follow a geographic gradient of variation, known as a cline. This clinal variation demonstrates that while some traits are more frequent in one geographic population, it does not mean that the trait is only found in that population.

 

2. Question: What are the three major stages of the human growth cycle and what happens during each one?

Response: The three major stages of the human growth cycle are the prenatal stage, the postnatal stage, and the adult stage. The prenatal stage includes the three trimesters of pregnancy and concludes with the birth of the child. During this stage, which lasts approximately 9 months, the fetus grows in size and its cells differentiate to form all the organs and tissues of the body. The postnatal stage begins at birth and concludes with the end of puberty. The postnatal stage includes several distinct periods. The neonatal period represents the first month after birth. The infancy period begins with the second month and ends when breastfeeding ceases. Next is the childhood period, which ends at age seven, followed by the juvenile period that terminates with the onset of puberty. Puberty is the final period of the postnatal stage. The adult stage includes both the reproductive and post-reproductive (also known as senescence) periods.

 

3. Question: How does the body adapt to temperature stress?

Response: The human body is homeothermic, meaning it can maintain a constant body temperature. However, when environmental temperatures are very hot or very cold, the body must adapt. In hot temperatures, the blood vessels closest to the surface of the body dilate. This vasodilation maximizes blood flow away from the core of the body, which reduces the overall temperature. In addition, the body starts to sweat. When the water evaporates from the surface of the skin, it reduces body temperature. In cold temperatures, the body begins to shiver, a heat-producing mechanism. Additionally, the blood vessels near the surface of the body constrict. The vasoconstriction reduces heat loss through reduced blood flow to the body surface. However, to prevent tissue damage to the extremities due to lack of blood flow and oxygen, the body must periodically dilate the blood vessels. After prolonged vasoconstriction, permanent tissue damage, known as frostbite, can occur.

See Figure 5.14 Berggman's Rule

 

4. Question: What are the two conditions of nutritional adaptation and what are the features of each?

Response: Malnutrition refers to the general condition of improper nutrition, which can include both a deficiency in calories and/or nutrients or an overabundance of calories. Undernutrition occurs from inadequate of calories and/or nutrients. In children, it frequently results in slowed body growth, reduced height, greater susceptibility to disease and infection, and greater risk of acquiring a disease in adulthood. For both undernourished adults and children, there is an increased likelihood of early death. Overnutrition refers to the consumption of excess calories, leading to obesity. Obesity has been unequivocally linked to various other diseases and health risks, such as type 2 diabetes, high blood pressure, heart disease, stroke, and osteoarthritis. Like undernutrition, overnutrition can also lead to early death.

See Figure 5.21 Malnutrition & Height

 

5. Question: How does the human skeleton adapt to workload and activity?

Response: Adaptation to workload and activity involves the skeletal system. First, forces such as bending and torsion can work to increase the rigidity or strength of the bone, preventing fractures. The more activity and stress placed on the skeleton, the greater rigidity and density of the bones. Lack of activity is also reflected in the skeleton, as inactive individuals tend to have less dense bones, creating an overall weaker skeleton. Secondly, the shape of bones can be remodeled to reflect specific activities due to the action of tendons, ligaments, and muscles. Continual and repetitive activity causes the skeleton to become strengthened and reinforced in the areas where the soft tissues attach to the bone. Finally, the diameters of the long bones tend to be larger in active individuals than in those who are inactive.

See Figure 5.26 Bone Disuse