APES Chapter 7

alien species/nonnative species/exotic species/immigrant species/invasive species

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

annual

Plant that grows, sets seed, and dies in one growing season.

climax 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.

commensalism

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.

competition

Two or more individual organisms of a single species (intraspecific competition) or two or more individuals of different species (interspecific competition) attempting to use the same scarce resources in the same ecosystem.

constancy

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

disturbance

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.

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.

ecosystem services

Natural services or natural capital that support life on the earth and are essential to the quality of human life and the functioning of the world's economies.

epiphyte

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

foundation species

Species that plays a major role in shaping communities by creating and enhancing a habitat that benefits other species.

habitat fragmentation

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

host

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.

indicator species

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

inertia

Ability of a living system to resist being disturbed or altered.

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.

law of tolerance

The existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by the species.

mutualism

Type of species interaction in which both participating species generally benefit.

native species

Species that normally live and thrive in a particular ecosystem.

parasite

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. The parasite draws nourishment from and gradually weakens its host; it may or may not kill the host.

parasitism

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

pathogen

Organism that produces disease.

perennial

Plant that can live for more than 2 years.

pioneer community

First 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.

predation

Situation in which an organism of one species (the predator) captures and feeds on parts or all of an organism of another species (the prey).

predator

Organism that captures and feeds on parts or all of an organism of another species (the prey).

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, called the prey.

prey

Organism that is captured and serves as a source of food for an organism of another species (the predator).

primary succession

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

resilience

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 succession

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

species evenness

Abundance of individuals within each species contained in a community.

species richness

Number of different species contained in a community.

theory of island biogeography/species equilibrium model

The number of species found on an island is determined by a balance between two factors: the immigration rate (of species new to the island) from other inhabited areas and the extinction rate (of species established on the island). 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 different species (species diversity).

threshold effect

The harmful or fatal effect of a small change in environmental conditions that exceeds the limit of tolerance of an organism or population of a species.

tolerance limits

Minimum and maximum limits for physical conditions (such as temperature) and concentrations of chemical substances beyond which no members of a particular species can survive.