27 terms

Chapter 54: Ecosystems

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