DominantsThe few species that attain high abundances in a community.
Dynamic life tableThe age-specific survival and fecundity of a cohort followed from
birth to the death of the last individual. Also called a cohort life table.Ecological efficiencyThe percentage of energy in the biomass produced by one trophic
level that is incorporated into the biomass produced by the next higher trophic level.
Ecological longevityAverage length of life of individuals of a population under stated
conditions.
EcosphereSee biosphere.
EcosystemBiotic community and its abiotic environment. Can be at various scales,
but at the larger scale is synonymous with a landscape.
Ecosystem diversityThe variety of different ecosystems.
Ecosystems ecologyThe study of ecosystems, particularly the interactions of the whole
biota and their environments.
EcotoneTransition zone between two diverse communities (e.g. the tundra–boreal
forest ecotone).
Effective population size (Ne)The average size of a population expressed in terms
of the number of individuals assumed to contribute genes equally to the next
generation; generally smaller than the actual size of the population, depending on
the variation in reproductive success among individuals.
Emergent propertyA feature of a system not deducible from lower-order processes.
Endemic (i) In biodiversity, a species whose range is confined to a defined area. (Cf.
exotic, indigenous). (ii) In epidemiology, a parasitewhose prevalencedoes not exhibit
wide fluctuations through time in a defined host, host species, or host population.
EnvironmentAll the biotic and abiotic factors that actually affect an individual organ-
ism at any point in its life cycle.
Environmental stochasticity Random variation in the abiotic environment.
EpidemicA sudden, rapid spread or increase of a disease-causing parasitethrough
a human population. An epidemic is often the result of a change in circumstances
that favor pathogen transmission such as a rapid increase of host population
density, or the introduction of a new parasite (or genetic strain of a parasite) to a
previously unexposed host population.
EpizooticThe sudden spread of a disease-causing parasitethrough a non-human
population; equivalent to an epidemicin human populations.
Equilibrium isoclineA line on a population graph designating combinations of
competing populations, or predator and prey populations, for which the growth
rate of one of the populations is zero.
EruptionA sudden increase in a species population in a defined area. (Cf. irruption.)
EutrophicRich in the mineral nutrients required by green plants; usually applied to
an aquatic habitat with high productivity. (Cf. oligotrophic.)
EvapotranspirationSum total of water lost from the land by evaporation and plant
transpiration.
ExoticA species found outside its normal habitats. (Cf. endemic,indigenous.)
ExperimentA test of a hypothesis, either observational or manipulative. The experi-
mental method is the scientific method.
Exponential rate of increase (r)The natural log of the finite rate of increase. Also
called the instantaneous rate of increase.
ExtinctionThe disappearance of a species or other taxon from a region or biota.392 GLOSSARY
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