Fitness: The proportionate contribution
of an individual to future
generations. In other words, fitness is the number of offspring of
an individual that themselves reach reproductive age, compared to
the number produced by the other individuals in the population.
Scientific Method: The procedure by which scientific theory is formed.
Natural selection: The process by which
individuals that are better
adapted to an environment survive, reproduce, and leave more
descendants than other individuals (which are not as well adapted
to that environment). Thus, the environment "selects" those
individuals
which leave more descendants.
Charles Darwin: An Englishman who is
generally credited with
proposing in his book, On the Origin of Species, published in 1859,
the theory of evolution by natural selection.
Competitive exclusion: The (local)
extinction of a population,
which is an inferior competitor under prevailing circumstances.
Because of its inferiority in competing with other species for
resources, the species excluded cannot become permanently
reestablished.
Competitive coexistence: The coocurrence
in the same habitat of two
or more species which compete for resources. Although each species
would do better in the absence of the other, each is sufficiently
different in its requirements (e.g., its food, nesting sites,
microhabitat, etc.) so that it is not excluded entirely from the
habitat.
Competition: The process in which 2 or
more organisms
both require a resource which is in short supply. The process
results in a
decrease in fitness for both organisms.
Sexual dimorphism: The difference in the
appearance and morphology
of males and females. For example, males may be either larger (as
in
primates) or smaller (as in hawks) than females.
Sexual selection: The tendency for one
sex (usually females) to
prefer individuals of the other sex which express a certain
character to a greater degree. The expression of this character is
presumably associated with greater reproductive success in the
parents, which would be inherited by the offspring. Sexual
selection tends to lead to sexual dimorphism.
Heritability: The tendency for offspring
to resemble their parents.
Most characteristics important for survival have low heritability.
For example, body weight and egg production are very sensitive to
environmental factors.
Kin selection: The selection of individual
behavior that benefits
relatives, even at a personal disadvantage, since relatives share
genes with the individual. The genes ultimately benefit - are
passed
on to future generations and may increase in frequency - even
though the individual might suffer.
Territory: A space that is defended by an
individual. The space is
associated with an important resource, e.g., food or nesting sites.
Gene: The unit of inheritance. A gene
contains the genetic
information that is used to produce a polypeptide chain, the
building blocks of proteins. In other words, a gene may be
considered the blueprint for producing a visible character.
Social Darwinism: The idea that humans of
high social standing
possess superior genes, and are thereby justified in their higher
social position.
Sociobiology: The concept that behavior
has a genetic component.
Organisms behave the way they do because of the genes they carry,
and are not completely free to choose what they do.
Polygyny: The mating of one male with
more than one female.
Stabilizing selection: Intermediate
genotypes have the highest
fitness. An example is that human beings with average birth weights
have the highest fitness.
Directional selection: Better adapted
genotypes replace less
adapted genotypes in an altered environmental situation. For
example, the
local climatic change associated with forest thinning favors
colonizing species over climax species.
Disruptive selection: In an heterogeneous
environment, extremes of
the population have the highest fitness while intermediates do
least well.
Dominance status: Position in a social
hierarchy. The establishment
of a social hierarchy and dominance status within it depends on
constancy of group membership and the ability to recognize
individuals within the group.
Female choice: The idea that females
choose a mate among males who
compete for her attention.
Male competition: Males compete with one
another for the
opportunity
to breed with females. Males have bright colors, special plumage or
fur, own territories, advertise with song and behavior, and battle
one another for females.
Pleistocene: An epoch in the Quaternary
period of the Cenozoic era,
from 1,000,000 years ago to about 10,000 years ago. The social
evolution of man occurred during the Pleistocene epoch.
Dispersal: The complete and permanent
emigration of an individual
from an its home range. Generally in mammals and birds the
heterogametic sex disperses, i.e., male mammals and female birds.
Dispersal - breeding: The emigration of
adults between reproductive
episodes.
Dispersal - natal: The emigration of
young from their birthplace.
Sexual strategy: The guiding principle in
finding a mate. For
instance, a female might depend on finding a mate that could
provide
the resources necessary to make her reproductive efforts
successful.
A male might depend on finding a female that could successfully
produce offspring if mated.
Mating preferences: The qualities in one
sex that the opposite sex
finds attractive. For instance, females might place their emphasis
on wealth and ambition while males might be more sensitive to signs
of youth and fertility.
Cultural conditioning: Social experience
that shapes an
individual's
preferences, e.g., mating preferences.
Breeding dispersal: Movement of adults
between reproductive
episodes.
Natal dispersal: Emigration of young from
their birthplace.
Philopatric: Staying close to the
location where the individual was
born, as opposed to dispersing.
Ontogeny: The history of the development
of the individual
organism.
Levels of behavioral analysis: 1.
Proximate explanations - a)
ontogeny of behavior in individuals, and b) underlying
physiological
mechanisms of the behavior; 2. Ultimate explanations - a)
evolutionary origins of the behavior,
and b) effects of the behavior on fitness.
Nature-nurture controversy: The dispute
over whether behavior is
innate (coded for by genes and inherited from parents - i.e.,
instinctive) or acquired through experience (essentially by
cultural conditioning).
Nepotism: Favoring kin, i.e., giving
one's own relatives an
advantage over others merely because they share genes.
Heterogametic sex: That sex which
carries two unequal sex
chromosomes. Males are the heterogametic sex in mammals while
females are the heterogametic sex in birds.
Homogametic sex: That sex which
carries two equal sex chromosomes. Females are the homogametic
sex in mammals while males are the homogametic sex in birds,
butterflies and moths.
Social aggression hypothesis: The
suggestion that natal dispersal is
triggered by aggression directed at juveniles by members of their
own species.
Relative avoidance hypothesis: The
suggestion that young males
disperse as a result of trying to avoid their litter mates and/or
their mother.
Exogenous factor: An external influence
arising in the environment
of the individual.
Endogenous factor: An internal influence
arising from the body of
the individual.
Ontogenetic switch hypothesis: The idea
that when an individual
reaches a certain stage in its growth, a change is triggered in its
behavior. For example, when ground squirrels reach a certain
weight, they will disperse - that is, size triggers dispersal.
Correlation: The cooccurrence of two
events. The coincidence of the
two events does not prove a cause and effect relationship between
them. For instance, the fact that most car accidents occur close to
home does not mean that people are particularly careless near home
or that long trips are safe. The coincidence occurs because most
car trips begin at home and are relatively short.
Ectoparasite: A parasite that lives on
the surface of its host,
e.g., a flea or a tick.
Parasite: An organism which feeds on
another organism (the host)
usually without killing it.
Inbreeding: Mating with close relatives.
Often the offspring have
a fitness that is less than that of offspring resulting from
outbreeding. This inbreeding depression in fitness results from an
unusually high incidence of identical alleles that is produced by
mating of two individuals that possess identical copies of many
genes.
Obligate pair-forming: A species in which
individuals of opposite
sex always find a mate with which they live out the rest of their
lives.
Female-dominated primate: A primate
species in which the female is
dominated by the male, i.e., the female takes a subordinate social
position.
Primate solution: An evolutionary
adaptation to survival that is
characteristic of the primates - of the tree shrews, lemurs,
tarsiers, monkeys, apes, and man.
Allele: A particular form of a gene. For
example, the gene for eye
color may take 2 forms - an allele producing blue eye color and
another allele producing brown eye color. In this case there are 2
alleles for eye color. An individual possesses 1 allele on each of
his 2 chromosomes, with the result that each character expressed is
based on the products of two alleles.
Alcohol dehydrogenase: An enzyme
occurring in the stomach, which
breaks down alcohol before it enters the blood stream.
Cirrhosis: A buildup of connective tissue
fibers in an organ (such
as the liver) and an associated loss of normal organ function.
Dose effect: A certain quantity of a drug
has a greater effect on a
smaller body than on a larger body. Therefore, babies require less
medicine than adults do. Likewise, a woman, being smaller on the
average than a man, should show a greater degree of intoxication if
she consumes the same amount of alcohol as the man does.
Hormone: A chemical secreted into the blood.
The blood carries the hormone to all the body's cells. Only the target cells
of the hormone can respond to it and by a specific reaction. For example, the
pituitary gland (at the base of the brain) secretes antidiuretic hormone,
which causes the cells of the kidney to reabsorb water. Thus, the
pituitary gland conserves water and concentrates the urine by regulating the cells of
the kidney.
Last updated on January 30, 2004
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