Chapter 12 Human Variation and Adaptation

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Chapter 12 Human Variation and Adaptation

• Key Terms

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• DolichocephalicHaving 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.

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• Biological determinismThe 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.

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• 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.

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• Population geneticists Geneticists who study the
  frequencies of alleles, genotypes, and phenotypes
  in populations.
• Slash-and-burn agricultureA 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.

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• Balanced polymorphismThe 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.

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• 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.

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• Endogamy Mating with individuals from the same
  group.
• Exogamy Mating pattern whereby individuals
  obtain mates from groups other than their own.

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• Hardy-Weinberg theory of genetic equilibriumThe
  mathematical relationship expressingunder ideal
  conditionsthe 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.

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• 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.

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• 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).
• VasoconstrictionNarrowing of blood vessels,
  reducing blood flow to the skin. Vasoconstriction
  is an involuntary response to cold and reduces
  heat loss at the skins surface.

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• 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.

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• 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.

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• Endemic Continuously present in a population.