Environmental Problems, Their Causes, and Sustainability 1

artificial selection Process by whichhumans select one or more desirable genetictraits in the population of a plant or animalspecies and then use selective breeding to producepopulations containing many individualswith the desired traits. Compare geneticengineering, natural selection.asexual reproduction Reproduction inwhich a mother cell divides to produce twoidentical daughter cells that are clones ofthe mother cell. This type of reproduction iscommon in single-celled organisms. Comparesexual reproduction.atmosphere The whole mass of airsurrounding the earth. See stratosphere,troposphere.atmospheric pressure A measure of themass per unit area of air.atom Minute unit made of subatomic particlesthat is the basic building block of allchemical elements and thus all matter; thesmallest unit of an element that can existand still have the unique characteristics ofthat element. Compare ion, molecule.atomic number Number of protons in thenucleus of an atom. Compare mass number.autotroph See producer.background extinction Normal extinctionof various species as a result of changes inlocal environmental conditions. Comparemass depletion, mass extinction.bacteria Prokaryotic, one-celled organisms.Some transmit diseases. Most act asdecomposers and get the nutrients theyneed by breaking down complex organiccompounds in the tissues of living or deadorganisms into simpler inorganic nutrientcompounds.barrier islands Long, thin, low offshoreislands of sediment that generally run parallelto the shore along some coasts.basic solution Water solution with morehydroxide ions (OH ) than hydrogen ions(H ); water solution with a pH greater than7. Compare acid solution, neutral solution.benthos Bottom-dwelling organisms.Compare decomposer, nekton, plankton.beta particle Swiftly moving electronemitted by the nucleus of a radioactive isotope.See also alpha particle, gamma rays.bioaccumulation An increase in theconcentration of a chemical in specificorgans or tissues at a level higher thanwould normally be expected. Comparebiomagnification.biocentric Life-centered. Compareanthropocentric.biocides See pesticides.biodegradable Capable of being brokendown by decomposers.biodegradable pollutant Material thatcan be broken down into simpler substances(elements and compounds) by bacteriaor other decomposers. Paper and mostorganic wastes such as animal manure arebiodegradable but can take decades tobiodegrade in modern landfills. Comparedegradable pollutant, nondegradable pollutant,slowly degradable pollutant.biodiversity Variety of different species(species diversity), genetic variability amongindividuals within each species (geneticdiversity), variety of ecosystems (ecologicaldiversity), and functions such as energy flowand matter cycling needed for the survivalof species and biological communities (functionaldiversity).biofuel Gas or liquid fuel (such asethyl alcohol) made from plant material(biomass).biogeochemical cycle Natural processesthat recycle nutrients in various chemicalforms from the nonliving environment toliving organisms and then back to the nonlivingenvironment. Examples are the carbon,oxygen, nitrogen, phosphorus, sulfur,and hydrologic cycles.bioinformatics Applied science of managing,analyzing, and communicating biologicalinformation.biological amplification See biomagnification.biological community See community.biological diversity See biodiversity.biological evolution Change in thegenetic makeup of a population of a speciesin successive generations. If continued longenough, it can lead to the formation of anew species. Note that populations—notindividuals—evolve. See also adaptation, differentialreproduction, natural selection, theoryof evolution.biological oxygen demand (BOD)Amount of dissolved oxygen needed byaerobic decomposers to break down theorganic materials in a given volume ofwater at a certain temperature over a specifiedtime period.biological pest control Control of pestpopulations by natural predators, parasites,or disease-causing bacteria and viruses(pathogens).biomagnification Increase in concentrationof DDT, PCBs, and other slowlydegradable, fat-soluble chemicals inorganisms at successively higher trophiclevels of a food chain or web. Comparebioaccumulation.biomass Organic matter produced byplants and other photosynthetic producers;total dry weight of all living organisms thatcan be supported at each trophic level in afood chain or web; dry weight of all organicmatter in plants and animals in an ecosystem;plant materials and animal wastesused as fuel.biome Terrestrial regions inhabited bycertain types of life, especially vegetation.Examples are various types of deserts,grasslands, and forests.biopharming Use of genetically engineeredanimals to act as biofactories forproducing drugs, vaccines, antibodies,hormones, industrial chemicals such asplastics and detergents, and human bodyorgans.biosphere Zone of earth where life isfound. It consists of parts of the atmosphere(the troposphere), hydrosphere (mostlysurface water and groundwater), andlithosphere (mostly soil and surfacerocks and sediments on the bottomsof oceans and other bodies of water)where life is found. Sometimes called theecosphere.biotic Living organisms. Compare abiotic.biotic potential Maximum rate at whichthe population of a given species canincrease when there are no limits on its rateof growth. See environmental resistance.birth rate See crude birth rate.bitumen Gooey, black, high-sulfur,heavy oil extracted from tar sand and thenupgraded to synthetic fuel oil. See tar sand.breeder nuclear fission reactor Nuclearfission reactor that produces more nuclearfuel than it consumes by converting nonfissionableuranium-238 into fissionableplutonium-239.broadleaf deciduous plants Plants suchas oak and maple trees that survive droughtand cold by shedding their leaves andbecoming dormant. Compare broadleaf evergreenplants, coniferous evergreen plants.broadleaf evergreen plants Plants thatkeep most of their broad leaves yearround.Examples are the trees found in thecanopies of tropical rain forests. Comparebroadleaf deciduous plants, coniferous evergreenplants.buffer Substance that can react withhydrogen ions in a solution and thus holdthe acidity or pH of a solution fairly constant.See pH.calorie Unit of energy; amount of energyneeded to raise the temperature of 1 gramof water 1°C (unit on Celsius temperaturescale). See also kilocalorie.cancer Group of more than 120 differentdiseases, one for each type of cell in thehuman body. Each type of cancer producesa tumor in which cells multiply uncontrollablyand invade surrounding tissue.carbon cycle Cyclic movement of carbonin different chemical forms from the environmentto organisms and then back to theenvironment.carcinogen Chemicals, ionizing radiation,and viruses that cause or promote thedevelopment of cancer. See cancer. Comparemutagen, teratogen.carnivore Animal that feeds on other animals.Compare herbivore, omnivore.carrying capacity (K) Maximum populationof a particular species that a given habitatcan support over a given period.cell Smallest living unit of an organism.Each cell is encased in an outer membraneor wall and contains genetic material(DNA) and other parts to perform its lifefunction. Organisms such as bacteria consistof only one cell, but most of the organismswe are familiar with contain many cells. Seeeukaryotic cell, prokaryotic cell.G2GLOSSARY