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alien species

see nonnative species


plant that grows, sets seeds, and dies in one growing season


animal that feeds on other animals

climax community

see mature community


an interaction between organisms of different species in which one type of organism benefits and the other type is neither helped nor harmed to any great degree

competitive exclusion principle

no two species can occupy exactly the same fundamental niche indefinitely in a habitat where there is not enough of a particular resource to meet the needs of both species


in ecological terms, refers to the number of species in a community at each trophic level and the number of trophic levels in a community


ability of a living system, such as a population, to maintain a certain size


a discrete event that disrupts an ecosystem or community. examples of natural disturbances include fires, hurricanes, tornadoes, droughts, and floods. examples of human-caused disturbances include deforestation, overgrazing, and plowing

early successional plant species

plant species found in the early stages of succession that grow close to the ground, can establish large populations quickly under harsh conditions, and have short lives

ecological succession

process in which communities of plant and animal species in a particular area are replaced over time by a series of different and often more complex communities


plant that uses its roots to attach itself to branches high in trees, especially in tropical forests

exotic species

see nonnative species

exploitation competition

situation in which two competing species have equal access to a specific resource but differ in how quickly or efficiently they exploit it

habitat fragmentation

breakup of a habitat into smaller pieces, usually as a result human activities


plant-eating organism. examples are deer, sheep, grasshoppers, and zooplankton


maintenance of favorable internal conditions in a system despite fluctuations


plant or animal on which a parasite feeds

immature community

community at an early stage of ecological succession. it usually has a low number of species and ecological niches and cannot capture and use energy and cycle critical nutrients as efficiently as more complex, mature communities

immigrant species

see nonnative species

indicator species

species that serve as early warnings that a community or ecosystem is being degraded


ability of a living system to resist being disturbed or altered

interference competition

situation in which one species limits access of another species to a resource, regardless of whether the resource is abundant or scarce

interspecific competition

attempts by members of two or more species to use the same limited resources in an ecosystem

intraspecific competition

attempts by two or more organisms of a single species to use the same limited resources in an ecosystem

keystone species

species that play roles affecting many other organisms in an ecosystem

late successional plant species

mostly trees that can tolerate shade and form a fairly stable complex forest community

mature community

fairly stable, self-sustaining community in an advanced stage of ecological succession; usually has a diverse array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently than simpler, immature communities

midsuccessional plant species

grasses and low shrubs that are less hardy than early successional plant species


type of species interaction in which both participating species generally benefit

native species

species that normally live and thrive in a particular ecosystem

nonnative species

species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by humans


animal that can use both plants and other animals as food sources. examples are pigs, rats, cockroaches, and people


consumer organism that lives on or in and feeds on a living plant or animal, known as the host, over an extended period of time. it draws nourishment from and gradually weakens its host; it may or may not kill the host


interaction between species in which one organism, called the parasite, preys on another organism, called the host, by living on or in the host


plant that can live for more that 2 years


how long a pollutant stays in the air, water, soil, or body

pioneer community

fist integrated set of plants, animals, and decomposers found in an area undergoing primary ecological succession

pioneer species

first hardy species, often microbes, mosses, and lichens, that begin colonizing a site as the first stage of ecological succession


situation in which an organism of one species captures and feeds on parts or all of an organism of another species


organism that captures and feeds on parts or all of an organism of another species

predator-prey relationship

interaction between two organisms of different species in which one organism, called the predator, captures and feeds on parts or all of another organism


organism that is captured and serves as a source of food for an organism of another species

primary succession

ecological succession in a bare area that has never been occupied by a community of organisms


ability of a living system to restore itself to original condition after being exposed to an outside disturbance that is not too drastic

resource partitioning

process of dividing up resources in an ecosystem so that species with similar needs (overlapping ecological niches) use the same scarce resources at different times, in different ways, or in different places

secondary consumer

organism that feeds only on primary consumers

secondary succession

ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed

species equilibrium model

theory of island biogeography


ability of a living system to withstand or recover from externally imposed changes or stresses


ecological succession, primary succession, secondary succession


any intimate relationship or association between members of two or more species

symbiotic relationship

species interaction in which two kinds of organisms live together in an intimate association. members of the participating species may be harmed by, benefit from, or be unaffected by the interaction


process in which organisms patrol or mark an area around their home, nesting, or major feeding site and defend it against members or their own species

theory of island biogeography

the number of species found on an island is determined by a balance between two factors: the immigration rate from from other inhabited areas and the extinction rate. the model predicts that at some point the rates of immigration and extinction will reach an equilibrium point that determines the island's average number of species differently

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