Glossary

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E

Ecological energetics
The branch of ecology in which communities are studied from the point of view of the energy flowing through them.
Ecological niche
A term with alternative definitions, not all of them synonymous. To state two:
(i) the 'occupation' or 'profession' of an organism or species; or
(ii) the range of conditions, resource levels and densities of other species allowing the survival, growth and reproduction of an organism or species. Hence, if each condition, resource or other species is seen as a dimension, the niche is an n-dimensional hypervolume.
Economic injury level (EIL)
The level of pest abundance above which it costs less to control the pest than is saved by pest control, but below which it costs more than is saved.
Ecophysiology
The study of physiology and tolerance limits of species that enhances understanding of their distribution in relation to abiotic conditions.
Ecosystem
A holistic concept of the plants, the animals habitually associated with them and all the physical and chemical components of the immediate environment or habitat which together form a recognizable self-contained entity. The concept is due to Tansley (1935).
Ecotype
A subset of individuals within a species with a characteristic ecology.
Ectomycorrhiza
An association of a fungus and the root of a plant (usually a tree) in which the fungus forms a sheath around the root and penetrates between the cells of the host.
Ectoparasite
A parasite that lives on the surface of its host.
Ectotherm
An organism in which the body temperature relies on sources of heat outside itself.
Effective population size (Ne)
The size of a genetically idealized population with which an actual population can be equated genetically.
Electivity
A measure of the preference, or lack of it, shown by a consumer species for its range of prey.
Emergent properties
Properties not possessed by individuals or populations that become apparent only when the community is the focus of attention.
Emigration
The movement of individuals out of a population or from one area to another.
Endemic
Having their habitat in a specified district or area, or the presence of a disease at relatively low levels, all the time.
Endobiont (endosymbiont)
An organism which lives within the cells of a host organism in a mutualistic relationship or doing no apparent harm.
Endogenous rhythm
A metabolic or behavioral rhythm that originates within the organism and persists even when external conditions are kept constant.
Endotherm
An organism which is able to generate heat within itself to raise its body temperature significantly.
Environmental 'noise'
Extraneous background signals that tend to mask biotic processes.
Enzyme denaturation
Structural change in an enzyme, involving an unfolding of peptide chains and rendering the enzyme less soluble, produced by mild heat or various chemicals.
Ephemerals
Organisms with a short life cycle, especially plants whose seeds germinate, grow to produce new seeds and then die all in a short period within a year.
Epidemic
The outbreak of a disease which affects a large number and/or proportion of individuals in a population at the same time.
Epidemiology
The study of the occurrence of infectious diseases, their origins and pattern of spread through a population.
Equilibrium theory
A theory of community organization that focuses attention on the properties of the system at an equilibrium point, to which the community tends to return after a disturbance.
Equitability
The evenness with which individuals are distributed among species in a community.
Eukaryote
Organism with cells possessing a membrane-bound nucleus in which the DNA is complexed with histones and organized into chromosome, i.e. protozoans, algae, fungi, plants and animals.
Euphotic zone
The surface zone of a lake or ocean within which net primary productivity occurs.
Eutrophication
Enrichment of a water body with plant nutrients; usually resulting in a community dominated by phytoplankton.
Evapotranspiration
The water loss to the atmosphere from soil and vegetation. The potential evapotranspiration may be calculated from physical features of the environmental such as incident radiation, wind speed and temperature. The actual evapotranspiration will commonly fall below the potential depending on the availability of water from precipitation and soil storage.
Even distribution
The distribution of organisms in which the average distance between them is greater than would occur if they were distributed at random.
Evolutionarily stable strategy (ESS)
A strategy which, if adopted by most of a population, cannot be bettered by any other strategy, and will therefore tend to become established by natural selection.
Evolutionary trees
Lineages designed to show the evolutionary history of relationships between groups of organisms.
Exact compensation
Density dependence in which increases in initial density are exactly counterbalanced by increases in death rate and/or decreases in birth rate and/or growth rate, such that the outcome is the same irrespective of initial density.
Exogenous
Originating outside an organism.
Exploitation competition
Competition in which any adverse effects on an organism are brought about by reductions in resource levels caused by other, competing organisms.
Exploiter-mediated coexistence
A situation where predation promotes the coexistence of species amongst which there would otherwise be competitive exclusion.
Exponential growth
Growth in the size of a population (or other entity) in which the rate of growth increases as the size of the population increases.
Extinction
The condition that arises from the death of the last surviving individual of a species, group, or gene, globally or locally.
Extrafloral nectaries
Nectar secreting glands found on the leaves and other vegetative parts of plants.
Extrinsic factors
Literally, factors acting from outside. In ecology, physical and chemical features of the environment, and other organisms, are all extrinsic factors acting on an organism.

 
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