Chapter 12

Question 1

Polytypic

Answer 1

Referring to species composed of populations that differ in the expression of one or more traits.

Question 2

Hardy-Weinberg equilibrium

Answer 2

The mathematical relationship expressing— under conditions in which no evolution is occurring—the predicted distribution of alleles in populations; the central theorem of population genetics.

Question 3

Stress

Answer 3

In a physiological context,any factor that acts to disrupt homeostasis; more precisely, the body’s response to any factor that threatens its ability to maintain homeostasis.

Question 4

Homeostasis

Answer 4

A condition of balance, or stability, within a biological system, maintained by the interaction of physiological mechanisms that compensate for changes (both external and internal).

Question 5

Acclimatization

Answer 5

Physiological responses to changes in the environment that occur during an individual’s lifetime. Such responses may be temporary or permanent, depending on the duration of the environmental change and when in the individual’s life it occurs. The capacity for acclimatization may typify an entire population or species, and because it’s under genetic influence, it’s subject to evolutionary factors such as natural selection and genetic drift.

Question 6

Vasodilation

Answer 6

Expansion of blood vessels, permitting increased blood flow to the skin. Vasodilation permits warming of the skin and facilitates radiation of warmth as a means of cooling. Vasodilation is an involuntary response to warm temperatures, various drugs, and even emotional states (blushing).

Question 7

Vasoconstriction

Answer 7

Narrowing of blood vessels to reduce blood flow to the skin. Vasoconstriction is an involuntary response to cold and reduces heat loss at the skin’s surface.

Question 8

Hypoxia

Answer 8

Insufficient levels of oxygen in
body tissues; oxygen deficiency.

Question 9

Vectors

Answer 9

Agents that transmit disease from one carrier to another. Mosquitoes are vectors for malaria, just as fleas are vectors for bubonic plague.

Question 10

Endemic

Answer 10

Continuously present in a population.

Question 11

Zoonotic

Answer 11

Pertaining to a zoonosis (pl., zoonoses), a disease that’s transmitted to humans through contact with nonhuman animals.