1. Chapter 15 Human Variation and Adaptation
Key Terms

2. monogenism Theory that all humans were descended from a original pair of humans.
polygenism Theory that all humans were descended from a number of pairs of humans.

3. plasticity The ability of organisms to make alterations in order to respond to differing conditions.
dolichacephalic Having a long, narrow head in which the width measures less than 75 % of the length.

4. brachycephalic Having a broad head in which the width measures more than 80% of the length.
biological determinism Concept that various aspects of behavior are governed by biological factors; inaccurate association of various behavioral attributes with certain biological traits such as skin color.

5. eugenics Philosophy of “race improvement” through the forced sterilization of members of some groups and encouraged reproduction among others.
polytypic Referring to species composed of populations that differ with regard to the expression of one or more traits.

6. stress In a physiological context, any factor that acts to disrupt homeostasis; more precisely, the body’s repose to any factor that threatens its ability to maintain homeostasis.
homeostasis A condition of balance, or stability, within a biological system, maintained by the interaction of physiological mechanisms that compensate for changes.

7. acclimatization Physiological response to changes in the environment that occurs during an individual’s lifetime.
neural tube In early embryonic development, the anatomical structure that develops to form the brain and spinal cord.

8. spina bifida A condition in which the arch of one or several vertebrae fails to fuse and form a a protective barrier around the spinal cord.
vasodilation Refers to widening (dilation) of the capillaries near the skin's surface permitting "hot" blood from the body's core to dissipate heat to the surrounding air.

9. vasoconstriction Narrowing of blood vessels to reduce blood flow from the skin.
vectors Agents that serve to transmit diseases from one carrier to another.

10. endemic Continuously present in a population.
pathogens Substances or microorganisms, such as bacteria, fungi, or viruses, that cause disease.