GLOSSARY G9
oligotrophic lake Lake with a low supply of
plant nutrients. Compare eutrophic lake, mesotro-
phic lake.
omnivore Animal that can use both plants
and other animals as food sources. Examples
include pigs, rats, cockroaches, and humans.
Compare carnivore, herbivore.
open access renewable resource Renew-
able resource owned by no one and available for
use by anyone at little or no charge. Examples
include clean air, underground water supplies,
the open ocean and its fi sh, and the ozone layer.
Comparecommon property resource, private property
resource.
open sea Part of an ocean that lies beyond the
continental shelf. Compare coastal zone.
organic compounds Compounds containing
carbon atoms combined with each other and
with atoms of one or more other elements such
as hydrogen, oxygen, nitrogen, sulfur, phospho-
rus, chlorine, and fl uorine. All other compounds
are called inorganic compounds.
organism Any form of life.
output Matter, energy, or information leaving
a system. Compare input, throughput.
output pollution control Seepollution cleanup.
overfi shing Harvesting so many fi sh of a spe-
cies, especially immature individuals, that not
enough breeding stock is left to replenish the
species and it becomes unprofi table to harvest
them.
overgrazing Destruction of vegetation when
too many grazing animals feed too long and
exceed the carrying capacity of a rangeland or
pasture area.
ozone (O 3 ) Colorless and highly reactive gas
and a major component of photochemical smog.
Also found in the ozone layer in the strato-
sphere. See photochemical smog.
ozone layer Layer of gaseous ozone (O 3 ) in
the stratosphere that protects life on earth by
fi ltering out most harmful ultraviolet radiation
from the sun.
paradigm shift Shift in thinking that occurs
when the majority of scientists in a fi eld or
related fi elds agree that a new explanation or
theory is better than the old one
parasite Consumer organism that lives on or
in, and feeds on, a living plant or animal, known
as the host, over an extended period. The
parasite draws nourishment from and gradually
weakens its host; it may or may not kill the host.
Seeparasitism.
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. See host, parasite.
pathogen Living organism that can cause
disease in another organism. Examples include
bacteria, viruses, and parasites.
peer review Process of scientists reporting
details of the methods and models they used,
the results of their experiments, and the reason-
ing behind their hypotheses for other scientists
working in the same fi eld (their peers) to exam-
ine and criticize.per capita ecological footprint Amount of
biologically productive land and water needed
to supply each person or population with the
renewable resources they use and to absorb or
dispose of the wastes from such resource use. It
measures the average environmental impact of
individuals or populations in different countries
and areas. Compare ecological footprint.
per capita GDP Annual gross domestic prod-
uct (GDP) of a country divided by its total popu-
lation at midyear. It gives the average slice of the
economic pie per person. Used to be called per
capita gross national product (GNP). See gross
domestic product.
per capita GDP PPP (Purchasing Power
Parity) Measure of the amount of goods and
services that a country’s average citizen could
buy in the United States.
perennial Plant that can live for more than
2 years. Compare annual.permafrost Perennially frozen layer of the
soil that forms when the water there freezes.
It is found in arctic tundra.
perpetual resource Essentially inexhaust-
ible resource on a human time scale because
it is renewed continuously. Solar energy is an
example. Compare nonrenewable resource, renew-
able resource.
persistence (1) the ability of a living system,
such as a grassland or a forest, to survive moder-
ate disturbances (2) the tendency for a pollutant
to stay in the air, water, soil, or body. Compare
constancy, resilience.pest Unwanted organism that directly or indi-
rectly interferes with human activities.
petroleum Seecrude oil.
phosphorus cycle Cyclic movement of
phosphorus in different chemical forms from the
environment to organisms and then back to the
environment.photosynthesis Complex process that takes
place in cells of green plants. Radiant energy
from the sun is used to combine carbon dioxide
(CO 2 ) and water (H 2 O) to produce oxygen (O 2 ),
carbohydrates (such as glucose, C 6 H 12 O 6 ), and
other nutrient molecules. Compare aerobic respi-
ration, chemosynthesis.
physical change Process that alters one
or more physical properties of an element or
a compound without changing its chemical
composition. Examples include changing the
size and shape of a sample of matter (crushing
ice and cutting aluminum foil) and changing
a sample of matter from one physical state to
another (boiling and freezing water). Compare
chemical change, nuclear change.
phytoplankton Small, drifting plants, mostly
algae and bacteria, found in aquatic ecosystems.
Compareplankton, zooplankton.pioneer community First integrated set of
plants, animals, and decomposers found in an
area undergoing primary ecological succession.
Seeimmature community, mature community.pioneer species First hardy species—often
microbes, mosses, and lichens—that begin colo-
nizing a site as the fi rst stage of ecological suc-
cession. See ecological succession, pioneer community.
planetary management worldview World-
view holding that humans are separate from
nature, that nature exists mainly to meet our
needs and increasing wants, and that we can
use our ingenuity and technology to man-
age the earth’s life-support systems, mostly for
our benefi t. It assumes that economic growth
is unlimited. Compare deep ecology worldview,
environmental wisdom worldview, stewardship
worldview.
plankton Small plant organisms (phytoplank-
ton) and animal organisms (zooplankton) that
fl oat in aquatic ecosystems.
point source Single identifi able source that
discharges pollutants into the environment. Ex-
amples include the smokestack of a power plant
or an industrial plant, drainpipe of a meatpack-
ing plant, chimney of a house, or exhaust pipe
of an automobile. Compare nonpoint source.
pollutant Particular chemical or form of
energy that can adversely affect the health,
survival, or activities of humans or other living
organisms. See pollution.
pollution Undesirable change in the physi-
cal, chemical, or biological characteristics of air,
water, soil, or food that can adversely affect the
health, survival, or activities of humans or other
living organisms.
pollution cleanup Device or process that re-
moves or reduces the level of a pollutant after it
has been produced or has entered the environ-
ment. Examples include automobile emission
control devices and sewage treatment plants.
Comparepollution prevention.
pollution prevention Device, process, or
strategy used to prevent a potential pollutant
from forming or entering the environment or to
sharply reduce the amount entering the envi-
ronment. Compare pollution cleanup.
population Group of individual organisms of
the same species living in a particular area.
population change Increase or decrease in
the size of a population. It is equal to (Births
Immigration) (Deaths Emigration).
population density Number of organisms in
a particular population found in a specifi ed area
or volume.
population dispersion General pattern in
which the members of a population are arranged
throughout its habitat.
population distribution Variation of popula-
tion density over a particular geographic area or
volume. For example, a country has a high popu-
lation density in its urban areas and a much lower
population density in rural areas.