Glossary - Environmental Science - page 332

population size The number of individuals in a population at a given time.
potential energy The energy stored in an object or system; usually a form of mechanical energy, but may ori-
ginate from atomic or chemical energy.
precautionary principle The principle that a substance is assumed to be harmful until proven otherwise.
precipitation Condensation of atmospheric water vapor that is pulled to the Earth's surface by gravity, usually
in the form of rain, snow, sleet, or hail.
predation A species interaction in which one species hunts, captures, kills, and consumes another species.
prescribed burns The burning of forests under controlled conditions, usually to decrease the likelihood of
later, larger fires; also called controlled burns.
primary treatment The process by which a sewage treatment system physically removes suspended solids in
settling tanks.
producers Organisms that use solar energy (green plants) or chemical energy (cyanobacteria) to manufacture
organic compounds needed for their energy and nutrition.
pyramid of biomass A graphical representation showing the biomass at each trophic level in an ecosystem.
radon An extremely toxic, naturally occurring radioactive gas that is produced from the decay of radium,
which is, in turn, produced from the decay of uranium.
random distribution Distribution of organisms arbitrarily, with no organization or intention.
rangelands Large expanses of undeveloped land that mainly contain low vegetation such as grasses and shrubs
and are suitable for grazing of livestock.
reclamation The restoration of the land after disturbance from mining.
relative abundance The number of each species in an area in relation to other species.
remediation The cleanup of contaminated soil or water.
renewable resource A resource that can be replenished within a human lifetime, including trees, grasses, an-
imals, and water.
reservoir An artificial lake that is used to store water behind a dam; commonly constructed to supply a con-
stant source of water or to prevent downstream flooding; may be combined with a generator to produce hydro-
electric power.
resource partitioning The process by which species evolve to divide an area's resources, allowing decreased
competition for any one resource.
response The reaction of a plant or animal to a substance.
reverse faults Faults caused from compression of tectonic plates or rock strata.
r-selected species Small organisms that have short gestation times and produce thousands of offspring at one
time, therefore having high biotic potential.