Transcript Chapter 12 Human Variation and Adaptation

Chapter 12
Human Variation and Adaptation
Key Terms

Dolichocephalic
Having a long, narrow head in which the
width measures less than 75 percent of the
length.

Brachycephalic
Having a broad head in which the width
measures more than 80 percent of the length.

Biological determinism
The concept that various attributes and
behaviors are governed by biological
(genetic) factors; the inaccurate association
of behavioral attributes with certain biological
traits, such as skin color.

Eugenics
Philosophy of “race improvement” through
forced sterilization of members of some
groups and encouraged reproduction among
others; an overly simplified, often racist, view
that is now discredited.

Polytypic
Referring to species composed of populations
that differ with regard to the expression of one
or more traits.

Cline
A gradual change in the frequency of
genotypes and phenotypes from one
geographical region to another.

Population geneticists
Geneticists who study the frequencies of
alleles, genotypes, and phenotypes in
populations.

Slash-and-burn agriculture
A traditional land-clearing practice whereby
trees and vegetation are cut and burned. In
many areas, fields are abandoned after a few
years and clearing occurs elsewhere.

Balanced polymorphism
The maintenance of two or more alleles in a
population due to the selective advantage of
the heterozygote.

Lactose intolerance
The inability to digest fresh milk products,
caused by the discontinued production of
lactase, the enzyme that breaks down
lactose, or milk sugar.

Gene pool
The total complement of genes shared by
reproductive members of a population.

Breeding isolates
Populations that are clearly isolated
geographically and/or socially from other
breeding groups.

Endogamy
Mating with individuals from the same group.

Exogamy
Mating pattern whereby individuals obtain
mates from groups other than their own.

Hardy-Weinberg theory of genetic
equilibrium
The mathematical relationship expressing—
under ideal conditions—the predicted
distribution of alleles in populations; the
central theorem of population genetics.

Population genetics
A mathematical and statistical approach used
to measure and explain evolutionary change
in contemporary populations.

Neural tube
In early embryonic development, the
anatomical structure that develops to form the
brain and spinal cord.

Spina bifida
A condition in which the arch of one or
several vertebrae fails to fuse and form a
protective barrier around the spinal cord.

Vasodilation
Expansion of blood vessels, permitting
increased blood flow to the skin. Permits
warming of the skin and facilitates radiation of
warmth as a means of cooling. An involuntary
response to warm temperatures, various
drugs, and even emotional states (blushing).

Vasoconstriction
Narrowing of blood vessels, reducing blood
flow to the skin. Vasoconstriction is an
involuntary response to cold and reduces
heat loss at the skin’s surface.

Hypoxia
Lack of oxygen. Hypoxia can refer to reduced
amounts of available oxygen in the
atmosphere (due to lowered barometric
pressure) or to insufficient amounts of oxygen
in the body.

Pathogens
Substances or microorganisms, such as
bacteria, fungi, or viruses, that cause disease.

Pandemic
An extensive outbreak of disease affecting
large numbers of people over a wide area;
potentially, a worldwide phenomenon.

Vectors
Agents that transmit disease from one carrier
to another. Mosquitoes are vectors for
malaria, just as fleas are vectors for bubonic
plague.

Endemic
Continuously present in a population.