Population viability analysis (PVA)The strategic analysis of the ecological, economic,
and political issues and challenges related to the conservation of an endangered
species, community, or ecosystem.
Prevalence The proportion of the host population with infectionor disease, often
expressed as a percentage. A measure of how widespread is the infection or
disease.
Primary productionProduction by green plants. (Cf. secondary production.)
ProductionAccumulation of energy or biomass.
ProductivityThe rate at which energy is accumulated.Realized nicheThe set of resources and environmental conditions constrained by
competition or predation that allow a single species to persist in a particular region.
A subset of the fundamental niche.
RecruitmentIncrement to a natural population, usually from young animals or plants
entering the adult population.
RegulationOccurs when a population experiences density-dependent mortality or
birth rates.
Rescue effectPrevention of the extinction of a local population by immigration of
individuals from elsewhere, often from a more productive habitat.
Resilience(i) The rate at which a population returns to equilibrium after a dis-
turbance. (ii) The ability to withstand disturbance. (Cf. fragility, robust.)
ResourceA substance or object required by an organism for normal maintenance,
growth, and reproduction. (See also limiting resource.)
RespirationComplex series of chemical reactions in all organisms by which
energy is made available for use; carbon dioxide, water, and energy are the end
products.
RobustReferring to a habitat with relatively wide tolerance to disturbance. (See fragility,
resilience.)Secondary plant compoundsChemical products of plant metabolism specifically for
the purpose of defense against herbivores and disease organisms.
Secondary productionProduction by herbivores, carnivores, or detritus feeders. (Cf.
primary production.)
SenescenceProcess of aging.
SereA series of stages of community change in a particular area leading towards a
stable state, or climax.
Sex ratioRatio of the number of individuals of one sex to that of the other sex in
a population.
Shared predationA type of apparent competitionin which two species fall victim to
a single predator and may compete for enemy-free space in which to avoid the
predator.
SinkAn ecosystem, habitat, population, or community that receives input of mater-
ials or individual organisms. The population is not self-sustaining. (Cf. source.)
SourceAn ecosystem, habitat, population, or community from which materials or
organisms move. The population is self-sustaining. (Cf. sink.)
Source–sink metapopulationA metapopulation in which some local populations
(sources) have a positive growth rate at low densities and others (sinks) have a
negative growth rate in the absence of immigration.398 GLOSSARY
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