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Glossary: E is for ... ecology, exogen, and extinct
by Ariadne Unst

Glossary of E...

earthquake (n.)
Sudden motion or shaking in the Earth. Caused by the quick release in seismic waves of slowly accumulated energy. Often occurs along faults, tectonic plate boundaries, or the mid-oceanic ridges.

ecological diversity (n.)
The variety of unique biological communities on the Earth.

ecological niche (n.)
A "place" occupied by a particular species and providing all resources (shelter, temperature, food, water, etc.) that a species needs to survive. The physical, chemical, and biological conditions required by a species to survive, grow, and reproduce.

ecologist (n.)
A scientist that studies the relationships and interactions among organisms and their environment.

ecology (n.)
Scientific study of the relationships among organisms, and between organism the living and non-living aspects of their environments. Study of the interactions that determine distribution and abundance of organisms. First use by E.H. Haeckel (1869) in German, from oikos (Greek for home) and logos (Greek or discourse). For an introduction to ecology, see Ecology notes.

ecosystem (n.)
The basic unit in ecology. Includes both the organisms and the non-living environment. The entire complex of organisms and factors of environment in an ecological unit in a defined space. An ecosystem consists of both organic and inorganic components, and includes soil, plants, animals, climate, and physical geoography. A sustainable natural community, its living organisms, and the ways these organisms interact (especially through energy and nutrient flow) with the physical space and with each other. Populations are tied to the amount of energy captured by primary producers in an ecosystem.

ecotone (n.)
An zone of contention for dominance between different plant communities. A transition area, narrow or broad, between contiguous communities.

ecotype (n.)
A subspecies or variety adapted to a specific environment or set of conditions.

edaphic factors (n.)
The elements of that environment that determine, in combination, the nature of soils. Such factors include the alkalinity of the soil, the degree of moisture, and the degree of sunlight. From the Greek edaphos for floor, earth.

endangered species (n.)
A species that is in danger of extinction because it is so low in number or its habitat is disappearing too quickly. The time till a species goes extinct can be extimated from its birth and death rates. Given those rates, the smaller the population, the more likely is extinction to arrive sooner. This is because of random fluctuations in births and deaths, and because births and deaths have to be whole numbers.

endemic (adj.)
Native and restricted to a given area, which can be quite local or quite far-ranging (a region, state, country, or continent).

endocarp (n.)
The innermost layer of a pericarp; e.g., a cherry stone.

endogen (n.)
A monocotyledonous plant that increases with time by the growth of new tissue within. Compare with an exogen.

endosperm (n.)
A nutritive substances or tissue in seed plants within the embryo sac.

entire (adj.)
A type of leaf margin that is continuous and smooth.

entrainment (n.)
The process of particle lifting by an agent of erosion.

entropy (n.)
The measure of the disorder (randomness) of matter and energy in a system.

environment (n.)
Abiotic and biotic factors that influence:
(1) the life of an organism.
(2) the function of some nonliving natural system.

enzyme (n.)
A type of protein that can facilitate and regulate chemical reactions in cells.

ephemeral (n.)
DTransitory; lasting for a short time; describing a plant or flower that blooms for only a short time.

epicotyl (n.)
The portion of the young stem of a plant seedling that is above the cotyledons. Embryonic stem.

epigynous (adj.)
Having floral organs (stamens, petals, and sepals) near the summit of the ovary.
Compare with hypogynous.

epiphyte (n.)
An organism that grows on another plant but is not parasitic on it. A type of vegetation that gets physical support from the branches of other plants.

epiphytic (adj.)
Without soil roots; obtaining nutrients from air, rainwater, and organic debris.

equilibrium theory of island biogeography (n.)
The number of species on an island balances immigration (controlled by regional processes) against extinction (controlled by local processes).
The greater the separation of an island from others, the fewer the species that inhabit it.
Defined in 1967 by R.H.MacArthur and E.O.Wilson.

environmental lapse rate (ELR) (n.)
The rate of air temperature change with altitude. The average ELR in the troposphere is an air temperature decrease of 6.5 degrees Celsius per kilometer rise in elevation.

erosion (n.)
Removal of weathered sediment or rock by the wind, water, or ice.

eukaryote (n.)
Organism whose cells have a membrane-bound nucleus and where many specialized structures are located within their cell boundary. Genetic material is organized in such organisms into chromosomes residing in the nucleus.

evergreen (adj.)
Has green leaves year-round. The old leaves remain green until the new foliage develops. Contrast with deciduous.

evolution (n.)
The series of changes (such as mutation or natural selection) through which any organism acquires the characteristics that differentiate it from another organism. See also phylogeny.

excurrent branching (n.)
Tree growth in which the main axis continues to the top of the tree from which smaller, lateral branches arise. Example: conifers.

exocarp (n.)
The outermost layer of a pericarp; also called the epicarp.

exogen (n.)
A dicotyledonous plant that increases with time by the addition of successive concentric rings inside the previous growth and beneath the bark. Compare with an endogen.

exfoliating (adj.)
Peeling off in thin layers, like an onion skin.

exotic (adj.)
A plant that does not grow naturally in your area (or region, state, country, or continent).

exponential growth (n.)
Growth where the change in size or quantity (per unit of time) is some fraction of the previous size or quantity; specifically it dependends on population size. Also called geometric growth. Contrast with arithmetic growth.

extant (adj.)
Types or species that are currently living. Not extinct.

exotic (adj.)
Not native; introduced from elsewhere.

extinct (adj.)
Describes a type or species that is no longer living. The likelihood that a species is in danger of extinction can be calculated for endangered species.

ecology (n.)
From evolve, from the Latin evolvere (to roll out). For an introduction to evolution, see Evolution notes.