Page 731 - Environment: The Science Behind the Stories

oxygen The chemical element with eight pro- biochemical pathways. Compounds in the her- and after which the community may not return
tons and eight neutrons. A key element in the bicide atrazine kill plants by blocking key steps to its original state. Also known as a regime
atmosphere that is produced by photosynthesis. in the process of photosynthesis. shift.
ozone (O ) A molecule consisting of three peace park A transboundary park intended phosphorus cycle A major nutrient cycle con-
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atoms of oxygen. Absorbs ultraviolet radiation to help ease tensions by acting as a buffer be- sisting of the routes that phosphorus atoms take
in the stratosphere. Compare ozone layer and tween nations that have quarreled over bound- through the nested networks of environmental
tropospheric ozone. ary disputes. systems.
ozone-depleting substances Airborne chemi- peak oil Term used to describe the point of photic zone In the ocean or a freshwater body,
cals, such as halocarbons, that destroy ozone maximum production of petroleum in the the well-lit top layer of water where photosyn-
molecules and thin the ozone layer in the world (or for a given nation), after which oil thesis occurs.
stratosphere. production declines. This is also expected to photochemical smog “Brown-air” smog
be roughly the midway point of extraction of
ozone hole Term popularly used to describe the caused by light-driven reactions of primary
thinning of the stratospheric ozone layer that the world’s oil supplies. Compare Hubbert’s pollutants with normal atmospheric com-
occurs over Antarctica each year, as a result of peak. pounds that produce a mix of over 100 different
chlorofluorocarbons (CFCs) and other ozone- peat A kind of precursor stage to coal, pro- chemicals, ground-level ozone often being the
depleting substances. duced when organic material that is broken most abundant among them. Compare indus-
down by anaerobic decomposition remains trial smog.
ozone layer A portion of the stratosphere,
roughly 17–30 km (10–19 mi) above sea level, wet, near the surface, and poorly compressed. photoelectric effect Effect that occurs when
that contains most of the ozone in the atmos- peer review The process by which a manu- light strikes one of a pair of metal plates in a
phere. script submitted for publication in an academic photovoltaic cell, causing the release of elec-
journal is examined by specialists in the field, trons, which are attracted by electrostatic
who provide comments and criticism (gener- forces to the opposing plate. The flow of elec-
paleoclimate Climate in the geologic past.
ally anonymously) and judge whether the work trons from one plate to the other creates an
paper park A term referring to parks that are merits publication in the journal. electrical current.
protected “on paper” but not in reality.
pelagic Of, relating to, or living between photosynthesis The process by which auto-
paradigm A dominant philosophical and theo- the surface and floor of the ocean. Compare trophs produce their own food. Sunlight pow-
retical framework within a scientific discipline. benthic. ers a series of chemical reactions that convert
parasite The organism in a parasitic relation- permafrost In tundra, underground soil that re- carbon dioxide and water into sugar (glucose),
ship that extracts nourishment or some other mains more or less permanently frozen. thus transforming low-quality energy from the
benefit from the host. sun into high-quality energy the organism can
permanent gas A gas that remains at a stable use. Compare cellular respiration.
parasitism A relationship in which one organ- concentration in the atmosphere.
ism, the parasite, depends on another, the host, photovoltaic (PV) cell A device designed to
for nourishment or some other benefit while permit trading The practice of buying and collect sunlight and directly convert it to elec-
simultaneously doing the host harm. Compare selling government-issued marketable emis- trical energy by making use of the photoelec-
mutualism. sions permits to conduct environmentally tric effect.
harmful activities. Under a cap-and-trade sys-
parasitoid An insect that parasitizes other in- tem, the government determines an acceptable photovoltaic effect See photoelectric effect.
sects, generally causing eventual death of the level of pollution and then issues permits to phylogenetic tree A treelike diagram that rep-
host. Compare parasite. pollute. A company receives credit for amounts resents the history of divergence of species or
parent material The base geologic material in it does not emit and can then sell this credit to other taxonomic groups of organisms.
a particular location. other companies. Compare emissions trading physical hazard Physical processes that occur
system.
particulate matter Solid or liquid particles naturally in our environment and pose human
small enough to be suspended in the atmos- pest A pejorative term for any organism that health hazards. These include discrete events
phere and able to damage respiratory tissues damages crops that are valuable to us. The term such as earthquakes, volcanic eruptions, fires,
when inhaled. Includes primary pollutants is subjective and defined by our own economic floods, blizzards, landslides, hurricanes, and
such as dust and soot as well as secondary pol- interests and is not biologically meaningful. droughts, as well as ongoing natural phenom-
lutants such as sulfates and nitrates. An EPA Compare weed. ena such as ultraviolet radiation from sunlight.
criteria pollutant. pesticide An artificial chemical used to kill in- Compare biological hazard; chemical hazard;
passive solar energy collection An approach sects (insecticide), plants (herbicide), or fungi cultural hazard.
in which buildings are designed and building (fungicide). phytoplankton Microscopic photosynthetic
materials are chosen to maximize their direct petroleum See crude oil. However, the term is algae, protists, and cyanobacteria that drift near
absorption of sunlight in winter and to keep also used to refer to both oil and natural gas the surface of water bodies and generally form
the interior cool in the summer. Compare ac- together. the first trophic level in an aquatic food chain.
tive solar energy collection. Compare zooplankton.
pH A measure of the concentration of hydrogen
patch In landscape ecology, spatial areas within ions in a solution. The pH scale ranges from 0 Pinchot, Gifford (1865–1946) The first pro-
a landscape. Depending on a researcher’s per- to 14: A solution with a pH of 7 is neutral; solu- fessionally trained American forester, Pinchot
spective, patches may consist of habitat for a tions with a pH below 7 are acidic, and those helped establish the U.S. Forest Service. Today,
particular organism, or communities, or eco- with a pH higher than 7 are basic. Because the he is the person most closely associated with
systems. An array of patches forms a mosaic. pH scale is logarithmic, each step on the scale the conservation ethic.
pathogen A parasite that causes disease in its represents a 10-fold difference in hydrogen ion pioneer species A species that arrives earliest,
host. concentration. beginning the ecological process of succession
pathway inhibitor A toxicant that interrupts phase shift A fundamental shift in the overall in a terrestrial or aquatic community.
vital biochemical processes in organisms character of an ecological community, gener- placer mining A mining technique that in-
G-16 by blocking one or more steps in important ally occurring after some extreme disturbance, volves sifting through material in modern or

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