Environmental Problems, Their Causes, and Sustainability 1

plankton Small plant organisms (phytoplankton)and animal organisms (zooplankton)that float in aquatic ecosystems.plantation agriculture Growing specializedcrops such as bananas, coffee, andcacao in tropical developing countries, primarilyfor sale to developed countries.plasma An ionized gas consisting of electricallyconductive ions and electrons. It isknown as a fourth state of matter.plates See tectonic plates. Various-sizedareas of the earth’s lithosphere that moveslowly around with the mantle’s flowingasthenosphere. Most earthquakes and volcanoesoccur around the boundaries ofthese plates. See lithosphere, plate tectonics.plate tectonics Theory of geophysicalprocesses that explains the movements oflithospheric plates and the processes thatoccur at their boundaries. See lithosphere,tectonic plates.point source Single identifiable sourcethat discharges pollutants into the environment.Examples are the smokestack of apower plant or an industrial plant, drainpipeof a meatpacking plant, chimney of ahouse, or exhaust pipe of an automobile.Compare nonpoint source.poison A chemical that adversely affectsthe health of a living human or animal bycausing injury, illness, or death.politics Process through which individualsand groups try to influence or controlgovernment policies and actions that affectthe local, state, national, and internationalcommunities.pollutant Aparticular chemical or form ofenergy that can adversely affect the health,survival, or activities of humans or otherliving organisms. See pollution.pollution An undesirable change in thephysical, chemical, or biological characteristicsof air, water, soil, or food thatcan adversely affect the health, survival,or activities of humans or other livingorganisms.pollution cleanup Device or process thatremoves or reduces the level of a pollutantafter it has been produced or has enteredthe environment. Examples are automobileemission control devices and sewage treatmentplants. Compare pollution prevention.pollution prevention Device or processthat prevents a potential pollutant fromforming or entering the environment orsharply reduces the amount entering theenvironment. Compare pollution cleanup.polychlorinated biphenyls (PCBs) Groupof 209 different toxic, oily, synthetic chlorinatedhydrocarbon compounds that can bebiologically amplified in food chains andwebs.polyculture Complex form of intercroppingin which a large number of differentplants maturing at different times areplanted together. See also intercropping.Compare monoculture, polyvarietal cultivation.polyvarietal cultivation Planting a plot ofland with several varieties of the same crop.Compare intercropping, monoculture,polyculture.population Group of individual organismsof the same species living in a particulararea.population change An increase ordecrease in the size of a population. It isequal to (Births Immigration) (Deaths Emigration).population density Number of organismsin a particular population found in a specifiedarea or volume.population dispersion General pattern inwhich the members of a population arearranged throughout its habitat.population distribution Variation of populationdensity over a particular geographicarea. For example, a country has a highpopulation density in its urban areas and amuch lower population density in ruralareas.population dynamics Major abiotic andbiotic factors that tend to increase ordecrease the population size and age andsex composition of a species.population size Number of individualsmaking up a population’s gene pool.population viability analysis (PVA) Useof mathematical models to estimate a population’srisk of extinction. See minimumviable population.porosity Percentage of space in rockor soil occupied by voids, whether thevoids are isolated or connected. Comparepermeability.positive feedback loop Situation in whicha change in a certain direction providesinformation that causes a system to changefurther in the same direction. Compare negativefeedback loop.potential energy Energy stored in anobject because of its position or the positionof its parts. Compare kinetic energy.poverty Inability to meet basic needs forfood, clothing, and shelter.ppb See parts per billion.ppm See parts per million.ppt See parts per trillion.prairies See grasslands.precautionary principle When there isscientific uncertainty about potentially seriousharm from chemicals or technologies,decision makers should act to prevent harmto humans and the environment. See pollutionprevention.precipitation Water in the form of rain,sleet, hail, and snow that falls from theatmosphere onto the land and bodies ofwater.predation Situation in which an organismof one species (the predator) captures andfeeds on parts or all of an organism ofanother species (the prey).predator Organism that captures andfeeds on parts or all of an organism ofanother species (the prey).predator–prey relationship Interactionbetween two organisms of different speciesin which one organism, called the predator,captures and feeds on parts or all of anotherorganism, called the prey.preservationist Person concerned primarilywith setting aside or protecting undisturbednatural areas from harmful humanactivities. Compare conservation biologist,conservationist, ecologist, environmentalist,environmental scientist, restorationist.prey Organism that is captured and servesas a source of food for an organism ofanother species (the predator).primary consumer Organism that feedson all or part of plants (herbivore) or onother producers. Compare detritivore, omnivore,secondary consumer.primary pollutant Chemical that has beenadded directly to the air by natural eventsor human activities and occurs in a harmfulconcentration. Compare secondary pollutant.primary productivity See gross primaryproductivity, net primary productivity.primary sewage treatment Mechanicalsewage treatment in which large solids arefiltered out by screens and suspended solidssettle out as sludge in a sedimentation tank.Compare advanced sewage treatment, secondarysewage treatment.primary succession Ecological successionin a bare area that has never been occupiedby a community of organisms. See ecologicalsuccession. Compare secondary succession.probability A mathematical statementabout how likely it is that something willhappen.producer Organism that uses solarenergy (green plant) or chemical energy(some bacteria) to manufacture the organiccompounds it needs as nutrients fromsimple inorganic compounds obtainedfrom its environment. Compare consumer,decomposer.prokaryotic cell Cell that does not have adistinct nucleus. Other internal parts arealso not enclosed by membranes. Compareeukaryotic cell.proton (p) Positively charged particle inthe nuclei of all atoms. Each proton has arelative mass of 1 and a single positivecharge. Compare electron, neutron.pure free-market economic system Systemin which all economic decisions aremade in the market, where buyers and sellersof economic goods interact freely, withno government or other interference. Comparecapitalist market economic system.pyramid of energy flow Diagram representingthe flow of energy through eachtrophic level in a food chain or food web.With each energy transfer, only a small part(typically 10%) of the usable energy enteringone trophic level is transferred to theorganisms at the next trophic level.radiation Fast-moving particles (particulateradiation) or waves of energy (electromagneticradiation). See alpha particle, betaparticle, gamma rays.G14GLOSSARY