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
Selection Presssures
Factors in the environment that favor successful reproduction of individuals possessing heritable traits and that reduce viability and fertility of those individuals not possessing those traits
Critical Factor
The single environmental factor closest to a tolerance limit for a given species at a given time
Tolerance Limits
(Also Limiting Factors)
Chemical or physical factors that limit the existence, growth, abundance, or distribution of an organism
Indicators
(Also Indicator Species)
Those whose critical tolerance limits can be used to judge environmental conditions
Habitat
The place or set of environmental conditions in which a particular organism lives
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
Endemic
Not found anywhere else
Competitive Exclusion Principle
A theory that no two populations of different species will occupy the same niche and compete for exactly the same resources in the same habitat for very long
Resource Partitioning
In a biological community, various populations sharing environmental resources through specialization, thereby reducing direct competition
Speciation
The generation of a new species
Geographic Isolation
(Also Allopatric Speciation)
Species that arise from a common ancestor due to geographic barriers that cause reproductive isolation
Allopatric Specieation
Species that arise from a common ancestor due to geographic barriers that cause reproductive isolation
Sympatric Specieation
Species that arise from a common ancestor due to biological or behavioral barriers that cause reproductive isolation even though the organism live in the same place
Binomials
Two part names (genus and species, usually in Latin) invented by Carl Linneaus to show taxonomic relationships
Intraspecific Competition
In a community, competition for resources between members of a different species
Interspecific Competition
In a community, competition for resources among members of the same species
Predator-Meditated Competition
A situation in which predation reduces prey populations and gives an advantage to competitors that might not otherwise be successful
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
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
Mullerian Mimicry
Evolution of two species, both of which are unpalatable and, have poisonous stingers or some other defense mechanism, to resemble each other
Symbosis
The intimate living together of memebers of two different species; includes mutualism, commensalism, and, in some classifications, parasitism
Mutualism
A symbiotic relationship between individuals of two different species in which both species benefit from the association
Commensalism
A symbiotic relationship in which one member is benefited and the second is neither harmed nor benefited
Parasitism
A symbiotic relationship in which one member benefits and the other is harmed
Keystone Species
A species whose impacts on its community or ecosystem are much larger and more influential than would be expected from mere abundance
Primary Productivity
Synthesis of organic materials (biomass) by green plants using the energy captured in photosynthesis
Abundance
The number or amount of something
Diversity
The number of species present in a community (species richness), as well as the relative abundance of each species
Complexity
The number of species at each trophic level and the number of trophic levels in a community
Edge Effects
A change in species composition, physical conditions, or other ecological factors at the boundary between two ecosystems
Ecotones
Boundaries between two types of ecological communities
Climax Community
A relatively stable, long-lasting community reached in a successional series; usually determined by climate and soil type
Primary Succession
An ecological succession that begins in an area where no biotic community previously existed
Secondary Succession
Succession on a site where an existing community has been disrupted
Pioneer Species
In primary succession on a terrestrial site, the plants, lichens, and microbes that first colonize the site
Disturbance
A periodic, destructive events such as fire or floods; changes in an ecosystem that affect (positively or negatively) the organism living there
Disturbance-Adapted Species
Species that depend on disturbances to succeed