AP BIOLOGY EXAM REVIEW UNIT 8

abiotic

Nonliving; referring to the physical and chemical properties of an environment.

biotic

Pertaining to the living factors—the organisms—in an environment.

disturbance

A natural or human-caused event that changes a biological community and usually removes organisms from it. Disturbances, such as fires and storms, play a pivotal role in structuring many communities.

dispersal

The movement of individuals or gametes away from their parent location. This movement sometimes expands the geographic range of a population or species.

density

The number of individuals per unit area or volume.

survivorship curves

A plot of the number of members of a cohort that are still alive at each age; one way to represent age-specific mortality.

exponential growth

Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.

logistic growth

Population growth that levels off as population size approaches carrying capacity.

carrying capacity

The maximum population size that can be supported by the available resources, symbolized as K.

density dependent

Referring to any characteristic that varies with population density.

density independent

Referring to any characteristic that is not affected by population density.

K-selection

Selection for life history traits that are sensitive to population density; also called density-dependent selection.

r-selection

Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection.

ecological succession

Transition in the species composition of a community following a disturbance; establishment of a community in an area virtually barren of life.

interspecific interaction

A relationship between individuals of two or more species in a community.

competition

Competition for resources between individuals of two or more species when resources are in short supply.

predation

An interaction between species in which one species, the predator, eats the other, the prey.

herbivory

An interaction in which an organism eats parts of a plant or alga.

symbiosis

An ecological relationship between organisms of two different species that live together in direct and intimate contact.

parasitism

A symbiotic relationship in which one organism, the parasite, benefits at the expense of another, the host, by living either within or on the host.

mutualism

A symbiotic relationship in which both participants benefit.

commensalism

A symbiotic relationship in which one organism benefits but the other is neither helped nor harmed.

competitive exclusion

The concept that when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population.

resource partitioning

The division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting species.

niche

The sum of a species' use of the biotic and abiotic resources in its environment.

species diversity

The number and relative abundance of species in a biological community.

biomass

The total mass of organic matter comprising a group of organisms in a particular habitat.

trophic structure

The different feeding relationships in an ecosystem, which determine the route of energy flow and the pattern of chemical cycling.

food chain

The pathway along which food energy is transferred from trophic level to trophic level, beginning with producers.

food web

The interconnected feeding relationships in an ecosystem.

keystone species

Species having a disproportionate effect on the ecosystem

primary succession

A type of ecological succession that occurs in an area where there were originally no organisms present and where soil has not yet formed.

secondary succession

A type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil or substrate intact.

ecosystem

All the organisms in a given area as well as the abiotic factors with which they interact; one or more communities and the physical environment around them.

law of conservation of mass

A physical law stating that matter can change form but cannot be created or destroyed. In a closed system, the mass of the system is constant.

primary production

The amount of light energy converted to chemical energy (organic compounds) by the autotrophs in an ecosystem during a given time period.

trophic efficiency

The percentage of production transferred from one trophic level to the next.

decomposer

An organism that absorbs nutrients from nonliving organic material such as corpses, fallen plant material, and the wastes of living organisms and converts them to inorganic forms; a detritivore.

primary consumer

An herbivore; an organism that eats plants or other autotrophs.

secondary consumer

A carnivore that eats herbivores.

tertiary consumer

A carnivore that eats other carnivores.

primary producer

An autotroph, usually a photosynthetic organism. Collectively, autotrophs make up the trophic level of an ecosystem that ultimately supports all other levels.