abundance
	The number or amount of something.
Batesian mimicry
	Evolution by one species to resemble the coloration, body shape, or behavior of another species that is protected from predators by a venomous stinger, bad taste, or some other defensive adaptation.
climax community
	A relatively stable, long-lasting community reached in a successional series; usually determined by climate and soil type.
coevolution
	The process in which species exert selective pressure on each other and gradually evolve new features or behaviors as a result of those pressures.
commensalism
	A symbiotic relationship in which one member is benefited and the second is neither harmed nor benefited.
complexity (ecological)
	The number of species at each trophic level and the number of trophic levels in a community.
disclimax community
	See equilibrium community.
diversity (species diversity, biological diversity)
	The number of species present in a community (species richness), as well as the relative abundance of each species.
ecological development
	A gradual process of environmental modification by organisms.
ecological niche
	The functional role and position of a species (population) within a community or ecosystem, including what resources it uses, how and when it uses the resources, and how it interacts with other populations.
ecotone
	A boundary between two types of ecological communities.
edge effects
	A change in species composition, physical conditions, or other ecological factors at the boundary between two ecosystems. Some organisms flourish at this boundary and benefit from processes such as habitat fragmentation that increase edge area. Other organisms are harmed by increasing edge effects.
environmental indicators
	Organisms or physical factors that serve as a gauge for environmental changes. More specifically, organisms with these characteristics are called bioindicators.
equilibrium community
	Also called a disclimax community; a community subject to periodic disruptions, usually by fire, that prevent it from reaching a climax stage.
evolution
	A theory that explains how random changes in genetic material and competition for scarce resources cause species to change gradually.
fire-climax community
	An equilibrium community maintained by periodic fires; examples include grasslands, chaparral shrubland, and some pine forests.
habitat
	The place or set of environmental conditions in which a particular organism lives.
interspecific competition
	In a community, competition for resources between members of different species.
intraspecific competition
	In a community, competition for resources among members of the same species.
keystone species
	A species whose impacts on its community or ecosystem are much larger and more influential than would be expected from mere abundance. This could be a top predator, a plant that shelters or feeds other organisms, or an organism that plays a critical ecological role.
Muellerian mimicry
	Evolution of two species, both of which are unpalatable and have poisonous stingers or some other defense mechanism to resemble each other.
mutualism
	A symbiotic relationship between individuals of two different species in which both species benefit from the association.
natural selection
	The mechanism for evolutionary change in which environmental pressures cause certain genetic combinations in a population to become more abundant; genetic combinations best adapted for present environmental conditions tend to become predominant.
parasite
	An organism that lives in or on another organism, deriving nourishment at the expense of its host, usually without killing it.
patchiness
	Within a larger ecosystem, the presence of smaller areas that differ in some physical conditions and thus support somewhat different communities; a diversity-promoting phenomenon.
pathogen
	An organism that produces disease in a host organism, disease being an alteration of one or more metabolic functions in response to the presence of the organism.
pioneer species
	In primary succession on a terrestrial site, the plants, lichens, and microbes that first colonize the site.
plankton
	Primarily microscopic organisms that occupy the upper water layers in both freshwater and marine ecosystems.
predator
	An organism that feeds directly on other organisms in order to survive; live- feeders, such as herbivores and carnivores.
primary productivity
	Synthesis of organic materials (biomass) by green plants using the energy captured in photosynthesis.
primary succession
	An ecological succession that begins in an area where no biotic community previously existed.
resource partitioning
	In a biological community, various populations sharing environmental resources through specialization, thereby reducing direct competition. See also ecological niche.
secondary succession
	Succession on a site where an existing community has been disrupted.
structure
	(in ecological terms)  Patterns of organization, both spatial and functional, in a community.
symbiosis
	The intimate living together of members of two different species; includes mutualism, commensalism and, in some classifications, parasitism.
territoriality
	An intense form of intraspecific competition in which organisms define an area surrounding their home site or nesting site and defend it, primarily against other members of their own species.

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