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consists of all the organisms living in a community as well as all the abiotic factors with which they interact; can range from a microcosm like an aquarium to a large area such as a lake or a forest

primary producers

the trophic level that ultimately supports all others; consists of autotrophs

primary consumers

herbivores; eat plants and other primary producers

secondary consumers

carnivores that eat herbivores

tertiary consumers

carnivores that eat other carnivores


important group of heterotrophs; consumers that get their energy from detritus


nonliving organic material, such as the remains of dead organisms, feces, fallen leaves, and wood

primary production

the amount of light energy converted to chemical energy by autotrophs during a given time period

gross primary production (GPP)

the amount of light energy that is converted to chemical energy by photosynthesis per unit time

net primary production (NPP)

equal to gross primary production minus the energy used by the primary producers for respiration

limiting nutrient

the element that must be added in order for production to increase in a particular area


a process in which phytoplankton communities that had been dominated by diatoms or green algae became dominated by cyanobacteria

actual evapotranspiration

the annual amount of water transpired by plants and evaporated from a landscape, usually measure in millimeters

secondary production

the amount of chemical energy in consumers' food that is converted to their own new biomass during a given time period

production efficiency

the fraction of energy stored in food that is not used for respiration

trophic efficiency

the percentage of production transferred from one trophic level to the next. Trophic efficiencies must always be less than production efficiencies because they take into account not only the energy lost through respiration and contained feces, but also the energy in organic material in a lower trophic level that is not consumed by the next trophic level

turnover time

a small standing crop biomass compared to their production

green world hypothesis

terrestrial herbivores consume relatively little plant biomass because they are held in check by a variety of factors, including predators, parasites, and disease

biogeochemical cycles

the nutrient circuits that involve both biotic and abiotic components

critical load

the amount of added nutrient

biological magnification

a process when toxins become more concentrated in successive trophic levels of a food web

greenhouse effect

process that retains some of the solar heat when CO2 and water vapor intercept and absorb much of the reflected infrared radiation, re-reflecting some of it back toward Earth

nitrogen fixation

the conversion of N2 by bacteria to forms that can be used to synthesize nitrogenous organic compounds


decomposers decomposes organic nitrogen to NH4+ (ammonium)


NH4+ (ammonium) is converted to NO3- (nitrate) by nitrifying bacteria


the process in which denitrifying bacteria under anaerobic conditions use NO3- (nitrate) in their metabolism instead of O2 (oxygen) releasing N2

Gause's experiment

studied the effects of interspecific competition with two closely related species of protists, Aurelia and Caudatum

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