Glossary
G-
abiotic Physical and chemical components of the environment.
abundance (population size) The number of individuals in a population.
acid A substance that releases hydrogen ions upon dissociation when dissolved in water, resulting in reduced pH of the solution; acids neutralize bases.
acid deposition An inclusive term that includes both wet and dry deposition of acids.
acid mine drainage A problematic result of strip mining, in which surface flow of groundwater turns acidic as it percolates through mine wastes (tailings).
acid rain Acidified rainfall. See acid deposition.
adaptations Traits favored by natural selection for surviving and reproducing in a particular environment.
additive effect An interaction of two toxic substances wherein their combined toxicity is simply the sum of their individual effects.
aerosol Tiny particles of solid or liquid material suspended in air or other gas.
age structure The proportions of individuals of various ages in a population; the relative proportions of individuals of reproductive and pre-
A horizon (topsoil) Soil layer immediately below the O horizon that includes significant amounts of organic matter, generally expressed by dark color.
airshed A concept equivalent to a watershed or drainage basin but related to movements of air rather than water; typically behaves in an orderly way, thus can be used to track and manage air pollution.
allergen A substance that activates the immune system, inducing an allergic reaction.
allopatric (geographic) speciation A process by which new species are formed that occurs as the result of the division of a population into two geographically separate populations; over time, genetic differences arise and accumulate in the two separate populations, eventually leading to reproductive isolation.
ammonification The process by which decomposers break down proteins and amino acids, releasing nitrogen in the form of ammonia (NH3) or ammonium ion (NH4+).
anaerobic An environment without molecular oxygen (O2).
antagonistic effect An interaction of two toxic substances wherein the toxicity of one chemical is reduced in the presence of the second chemical, which may be used as an antidote.
Anthropocene era A new geologic era dominated by the effects of humans.
anthropocentric Human-
antibiotics Substances that suppress bacterial growth or attack and that are used in modern medicine in the treatment of bacterial diseases.
aquaculture The controlled growing of aquatic organisms (e.g., fish, shellfish, algae, or plants) as a crop, mainly for food; carried out in marine, brackish water, or freshwater environments.
aquifer A geologic formation containing groundwater; gains water through the process of infiltration and loses water through groundwater flow.
artificial selection A process in which humans “select” which individuals in a population mate to produce descendants with desired characteristics.
asthenosphere The layer of the upper mantle immediately below the lithosphere; has an overall consistency similar to plastic.
atom The smallest particle of a substance that still retains the properties of the substance.
atomic number The number of protons in the nucleus of an atom of an element; equal to the number of electrons in a neutral atom.
atomic weight The average mass of the atoms in a naturally occurring pure substance (e.g., gold, carbon, oxygen).
ATP (adenosine triphosphate) An energy-
autotroph See primary producer.
background extinction Average rate of extinction occurring over long periods of time between periods of mass extinction.
bacteria Single-
base A substance that has the capacity to neutralize acids; bases release hydroxide ions (OH–) and react with acids to form a salt and water.
B horizon A depositional soil layer in which materials transported from the A and E horizons accumulate.
bioaccumulation The absorption and increase in concentration of chemicals in organisms, over time, including potentially toxic chemicals. See biomagnification.
biocentric Centered on life in all its forms; for example, biocentric environmental ethics extends moral obligation to all life.
biochemical oxygen demand (BOD) An indicator of the amount of organic matter in water, measured as the quantity of oxygen consumed by microorganisms as they break down the organic matter in a sample of water.
biodegradable A substance that can be decomposed to its chemical constituents by biological processes.
biodiesel A liquid fuel made from vegetable oils and animal fats.
biodiversity Biological variety from genes and species to diversity at the scale of ecosystems and the globe.
biodiversity hotspot A region that supports at least 1,500 endemic plant species, approximately 0.5% of the world total, and that has been reduced in area by at least 70%.
biofuel A liquid or gaseous fuel derived from biomass (e.g., ethanol, biodiesel).
G-
biogeochemical cycle The cyclic path of an inorganic substance, such as phosphorus, nitrogen, or carbon, through the Earth system, including the atmosphere, Earth’s crust, oceans, lakes, and rivers; key biological components are producers, consumers, detritivores, and decomposer bacteria and fungi.
biological environment The kinds and diversity of pathogens, predators, parasites, and competitors with which an organism interacts.
biomagnification An increase in concentration of a substance (e.g., heavy metals or fat-
biomass fuel A combustible fuel derived from biological materials (e.g., wood, charcoal, dung).
biome Associations of plants, animals, and other organisms that occur over large areas and that are characterized by distinctive biological structure, especially by characteristic growth forms (e.g., trees, shrubs, or grasses on land; corals, kelp, or mangrove trees in aquatic environments).
bioreactor A system designed to cultivate algae; helps filter wastewater before it enters the environment.
bioremediation An approach to pollution cleanup that employs organisms, generally microbes or plants, to decontaminate soils, sediments, and groundwater aquifers in place.
biotechnology The application of engineering techniques to modify organisms genetically for a particular purpose.
biotic Living components of the environment.
bitumen A flammable, highly viscous or semisolid mixture of hydrocarbons.
black market The exchange of illegal goods and services.
boom A barrier used to contain oil slicks and prevent them from entering sensitive coastal areas.
bottom ash The ash that accumulates at the bottom of an incinerator during the combustion of solid waste.
bottom trawlers Weighted nets dragged along the ocean to catch groundfish (e.g., cod, flounder, scallops, shrimp, crab).
brackish water Natural waters with a salt content intermediate between freshwater and seawater, commonly occurring near the mouths of rivers where freshwater and seawater mix.
brownfield An abandoned industrial site generally contaminated with hazardous waste and unusable without remediation.
Bt Insect-
buffer zone A zone around a nature reserve or protected area in which limited economic activity is allowed.
buffering capacity A measure of the ability of a solution to neutralize acid.
bushmeat The butchered meat of wild animals, most commonly from African forests.
bycatch Discarded catch and mortality of any organism (e.g., fish, invertebrate animals, birds, dolphins, sea turtles) as a result of contact with fishing gear.
cap and trade Systems for regulating the emission of carbon dioxide and other pollutants.
carbon capture and sequestration A technological strategy to reduce additions of carbon dioxide and other greenhouse gases to the atmosphere by collecting them at the point of emission and storing them in a place or chemical form that removes them from active circulation in the carbon cycle.
carbon credit A permit to produce a certain amount of carbon emissions, which can be traded or sold, if the full emissions allowance is not used.
carbon cycle The cycling of carbon through the Earth system; key biological processes in the carbon cycle include photosynthesis, respiration, and decomposition.
carbon footprint The total amount of CO2 and other greenhouse gases produced over the course of the life cycle of a particular technology, individual, or population—
carbon sink A part of the Earth system that takes carbon compounds from the atmosphere, through biological or physical processes, and removes them from active circulation.
carbon taxes Tax on carbon emissions.
carcinogen A substance that causes cancer by directly damaging the DNA of cells.
carnivore (predator) An animal that feeds on other living animals (e.g., a lion or a spider).
carrying capacity (K) The number of individuals in a population that an environment can support over the long term.
catch-
catch-
cellular respiration A process taking place in cells that requires oxygen. During cellular respiration, molecules, such as glucose, are broken down and energy, water, and carbon dioxide are released.
cellulosic ethanol Ethanol produced from wood and other cellulose-
centrally planned economy An economy in which decisions about the production and consumption of goods and services are made by a central authority. See market economy.
channelize To engineer a change to the natural form of a stream or river, including straightening, deepening, or widening the channel.
chemical energy A form of potential energy; energy stored in the bonds of molecules, such as sugars, fats, or methane.
chemical reaction A process by which new substances are produced via the rearrangement of the atoms undergoing the reaction, generally through the exchange or sharing of electrons.
child mortality rate The number of infants per 1,000 live births who die before reaching 5 years of age.
C horizon The deepest soil layer, consisting mainly of lightly weathered parent material.
clear-
climate The average weather occurring across a region over a long period, including average temperatures, precipitation, and so forth.
climate adaptation A strategy to reduce the impacts and hazards associated with climate change.
climax community The community at the end of a successional sequence that persists until a disturbance disrupts it sufficiently to restart succession.
coal Sedimentary or metamorphic rock high in carbon and energy content formed over millions of years under conditions of high pressure and temperature (lignite, sub-
cogeneration Generally refers to the use of a single source of energy for multiple purposes.
G-
combined cycle power plants Power plants that combine a gas turbine engine with a steam power plant.
command-
commercial fishing Catching fish for profit; represents the vast majority of the fish captured around the world.
common-
common property Property owned or controlled by a community, such as an indigenous tribe.
competition Interactions among individuals that depend on the same resources; generally results in reduced growth, reproduction, or survival of one or both competitors.
competitive exclusion principle If two species with identical niches compete for a limited resource (e.g., nectar), one or the other will be a better competitor and will eventually eliminate the other species.
composting A process involving aerobic decomposition of organic material used to recycle garden waste and organic components of municipal solid waste.
compound A substance composed of a fixed ratio of two or more elements (e.g., water, which consists of two hydrogen atoms and one oxygen atom: H2O). Compounds can be broken down into the elements of which they are made via chemical or physical processes.
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Superfund Law enacted in 1980 to regulate hazardous waste and require companies to dispose of it safely.
conflict of interest Competing interests, including personal, philosophical, and financial interests, that may interfere with an objective judgment.
conservation The preservation, wise use, or restoration of species, ecosystems, or natural resources.
conservation ethic A philosophy of resource management that promotes the efficient use of natural resources to provide the greatest good to the greatest number of people.
conservation of matter A physical law describing how during chemical reactions matter is neither created nor destroyed but conserved.
constructed wetlands Artificial wetland ecosystems, used in the treatment of wastewater, that are constructed in areas where wetlands may not occur naturally.
consumer An organism that meets its dietary needs by feeding on other organisms or on organic matter produced by other organisms. See heterotroph.
containment structure A steel and concrete enclosure designed to prevent the release of radioactive material in the case of a serious nuclear reactor accident.
control group A baseline for comparisons.
control rods Long rods made of neutron-
convection cell Pattern of circulation caused by differing temperatures in a liquid or gas due to, for example, varying temperatures in Earth’s semi-
Convention on Biological Diversity An international agreement negotiated under the sponsorship of the United Nations Environmental Programme to promote the conservation of biological diversity, the sustainable use of its components, and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources.
conventional-
core The core of Earth consists of an outer liquid layer of molten iron and nickel and a solid, inner iron–
Coriolis effect A deflection in the winds from a straight north–
corrosive Capable of causing permanent damage to a variety of surfaces, including living tissue; corrosive substances include strong acids (pH of 2 or less) or strong bases (pH of 12 or greater).
covalent bond A bond between atoms that share one or more pairs of electrons.
criteria pollutants Very common sources of air pollution (e.g., sulfur dioxide) chosen by the EPA to be regulated because they are hazardous to human health and the environment.
critical habitat Areas that are essential for the survival of a listed endangered or threatened species.
crop rotation A method farmers use to maintain soil fertility and reduce the buildup of pests by rotating crops on two-
crust The relatively low-
cultural eutrophication An accelerated process of eutrophication resulting from human activities (e.g., sewage disposal, agriculture) that increase the rate of nutrient addition to ecosystems; generally results in excessive algal or plant production, depletion of dissolved oxygen in aquatic ecosystems, and loss of biodiversity.
dam A structure that blocks the flow of a stream or river; may be used to reduce downstream flooding or to store water in a reservoir.
data The measurements made during a scientific study.
debt-
decomposer An organism, mainly fungi and bacteria, that breaks down dead plant and animal tissues, promoting the process of decomposition. See detritivore.
demanufacturing The dismantling of equipment, especially electronics, into constituent components and scrap metals that can be reused or recycled.
demographic transition A theory proposing that, with improved living conditions, human populations will undergo a gradual change from an earlier state of high death rates and birthrates to a state of low death rates and birthrates, with improved living conditions. The demographic transition model fits the history of today’s developed countries well.
demography The statistical study of populations, generally human populations, including their density, growth, age structure, birthrates, and death rates.
denitrification The process by which specialized bacteria in soil and water convert nitrate ions back into nitrogen gas (N2), which returns to the atmosphere.
density-
density-
G-
desalination The process of removing salts from seawater or brackish water to form freshwater.
desertification A process of degradation of once fertile lands to a desertlike condition of reduced plant cover and primary production.
detritivore An organism that feeds on dead organic matter (e.g., fallen leaves on the floor of a forest). Detritivores help in the process of decomposition; examples include many insects and earthworms. See decomposer.
discharge In an aquifer, the movement of water from the groundwater to a body of surface water (e.g., a river or lake).
disease A condition in which normal biological function is impaired by bacteria, viruses, parasites, improper diet, or pollutants.
dispersant A chemical used in oil spill cleanup that thins and dissolves the thick crude.
distillation A desalination process that uses heat to evaporate water from seawater or brackish water and condenses the resulting salt-
distribution The geographic range of a species.
disturbance A discrete event (e.g., a fire, earthquake, or flood) that disrupts a population, ecosystem, or other natural system by changing the resources available or by altering the physical environment.
DNA (deoxyribonucleic acid) The carrier of genetic information in cells, consisting of two complementary chains of molecules, called nucleotides, wound in a double helix; this source of biological inheritance, passed from parents to offspring, directs the development and functioning of an organism.
domestication The deliberate change of a wild animal or plant population through selective breeding to better meet the needs of humans.
dose–
drought An extended period of dry weather during which precipitation is reduced sufficiently to damage crops, impair the functioning of natural ecosystems, or cause water shortages for human populations.
dry casks Steel and concrete structures used for temporary storage of nuclear waste.
eccentricity Variation in the shape of Earth’s orbit around the Sun.
ecocentric Centered on entire ecosystems; for example, ecocentric environmental ethics extends moral obligation to the nonliving components of the environment, emphasizing the integrity of whole natural systems.
ecological community All the species—
ecological economics A branch of economics that draws on many disciplines in studies of the influence of economic activity on the environment in an attempt to build a conceptual bridge between humans and human institutions and the rest of nature.
ecological footprint The environmental impact of a human population as the area of land and sea needed to produce the resources it consumes and to absorb the wastes it produces.
economic externality A cost or benefit to the environment or to society resulting from the production and use of a product that is not included in the market price of the product.
economic system A network of people, institutions, and commercial interests involved in the production, distribution, and consumption of goods and services.
economics A social science that deals with the production, distribution, and consumption of goods and services, as well as the theory and management of economic systems.
ecosystem The organisms living in a place and the biological, physical, and chemical aspects of the environment with which they interact. Ecosystem ecologists focus much of their research on the flux and transformation of matter and energy.
ecosystem-
ecosystem diversity A measure of the variety and extent of ecosystems in an area.
ecosystem engineer A species, like the beaver, that influences ecosystem structure and processes by altering the physical environment.
ecosystem services The benefits that humans receive from natural ecosystems such as food, water purification, pollination of crops, carbon storage, and medicines.
ecotourism Recreational travel that helps conserve the environment and improves the well-
edge effects Environmental conditions occurring near the edge of an ecosystem (e.g., near the edge of an isolated forest fragment); conditions at edges differ from those deep in the ecosystem interior.
E horizon Soil layer between the A and B horizons, from which clays and dissolved materials are transported down the soil profile to the underlying B horizon.
electron A subatomic particle with a negative charge (–1) and atomic mass of 1.
electronic waste (e-
element A substance composed of a single type of atom, such as hydrogen, helium, iron, or lead, that cannot be broken down into simpler substances via chemical or physical means.
El Niño A period of warmer than average sea surface temperatures and lower barometric pressure in the eastern Pacific Ocean, favoring the production of storms in the eastern Pacific Ocean.
El Niño Southern Oscillation An oscillating climatic system involving variation in ocean surface temperatures and barometric pressures across the Pacific Ocean.
emigration The movement of individuals out of one area, or country, to another.
endangered species A species whose populations have become so small that they may become extinct in the near future.
Endangered Species Act of 1973 (ESA) Legal protection in the United States for both domestic and foreign endangered species that declared plants and all invertebrate animals eligible for protection.
endemic species Local or regional species of organisms found nowhere else on Earth.
endocrine disruptor A chemical that mimics hormones, including female hormones (estrogen and progesterone), male hormones (testosterone), or thyroid hormones.
energy The capacity to do work. See work.
energy pyramid A graphic representation of the distribution of energy among trophic levels in an ecosystem. Because large amounts of energy are dissipated at every trophic level, these diagrams take the form of a pyramid.
G-
energy return on energy investment (EROEI) The ratio of the energy content of an energy source (e.g., gasoline) to the amount of energy that must be used in, for example, drilling, transporting, and refining to produce the energy source.
energy subsidies Government policies aimed at lowering the costs of energy production or lowering the cost to energy consumers.
enrichment A nuclear process in which uranium-
entropy A measure of the amount of disorder in a system.
environment The physical, chemical, and biological conditions that affect an organism.
environmental economics A branch of economics that draws mainly from the field of economics as it assesses and manages the costs and benefits of economic impacts on the environment.
environmental ethics The branch of philosophy that concerns the moral responsibilities of humans with regard to the environment.
environmental hazards Phenomena dangerous to humans, including infectious disease, toxic substances, and pollutants.
environmental health An area of research and action that assesses and attempts to mitigate the physical, chemical, and biological factors in the environment that impact human health.
environmental justice The fair treatment and meaningful involvement of all people in the development, implementation, and enforcement of environmental laws, regulations, and policies.
environmental science Study of the influence of humans on the environment and the effects of the environment on humans; also attempts to find ways of reducing human harm to the environment.
environmentalism An ideological and social movement that advocates the protection of the environment from human harm through political action and education.
equilibrium model of island biogeography The hypothesis that the number of species on an island is determined by a balance between rates of immigration of new species and rates of species extinction on the island, where rates of species immigration and extinction are determined by island size and isolation from sources of immigrants.
erosion A process that removes geologic materials, ranging from clay-
euphotic zone A surface layer of the oceans and deep lakes where there is sufficient light to support photosynthetic aquatic organisms.
eutrophication A natural process by which nutrients, especially those that limit primary production, build up in an ecosystem.
evolution A change in the genetic makeup of a population as a consequence of one of several different processes, including natural selection and selective breeding.
exposure assessment An assessment of the population that might be exposed to an agent of concern and of potential routes of exposure.
extinction The loss of all members of a species.
field experiments Experiments in which the experimenter generally controls or manipulates a single factor, the factor of interest, while allowing all other factors to vary normally.
fire regime The frequency and intensity of fires that typically occur in a particular ecosystem.
first law of thermodynamics A physical law concerned with the conservation of energy: Though one form of energy may be transformed to other forms, the total amount of energy in a system plus its surroundings is conserved; that is, the total amount of energy remains the same. See second law of thermodynamics.
fisheries collapse The decline in a certain species’ annual catch below 10% of its historic catch.
fishery A population of fish or shellfish, and the economic system involved in harvesting the population, often identified by the geographic area where the fish or shellfish are harvested.
flagship species A species that attracts and sustains human interest in protecting ecosystems.
flammable Easily ignited; a flammable substance can ignite and burn easily (e.g., from friction, absorption of moisture, or contact with other waste materials).
flood A river or stream overflowing its banks and inundating the surrounding landscape known as the floodplain.
floodplain The area of land that stretches from a water channel to the valley walls.
flux The rate of flow of materials or energy across a given area (e.g., the flow of water vapor from the ocean’s surface to the atmosphere or the flow of radiant energy between an organism and its surroundings).
fly ash Particles formed during combustion that are light enough to become airborne and exit a combustion chamber with exhaust gases, including soot and dust.
food web A set of feeding relationships among organisms indicating the flow of energy and materials in an ecosystem.
forestry The management of forests and woodlands for the harvest of timber or fuelwood.
fossil fuels Fossilized organic material, mainly the remains of ancient photosynthetic organisms that converted the Sun’s radiant energy into chemical energy (e.g., coal, oil, natural gas).
foundation species A species that strongly influences community structure by creating environments suitable for other species by virtue of its large size or biomass.
fracking (hydraulic fracturing) A controversial extraction technique that involves drilling horizontally into a rock formation and pumping in a mixture of fluids and sands to fracture it, thus creating a path through which natural gas or oil can flow out.
freshwater Water with a salt content, or salinity, below that of brackish water (i.e., salinity less than 500 mg/l).
fuel rods Tubes containing small pellets of uranium-
gas turbine engine Engine that burns natural gas, sending a hot, high-
gasification A technique to make carbon capture at coal-
genes Stretches of DNA that direct the growth, development, and functioning of organisms.
genetic diversity The sum of the different genes and gene combinations found within a single population of a species and across populations of the same species.
G-
genetically modified (GM) organism (GMO) An organism into which one or more genes have been incorporated using the techniques of biotechnology.
geoengineering Proposed technological approaches to manipulating processes that influence climate, such as carbon dioxide uptake by marine algae, in an effort to mitigate global climate change.
geo-
gillnetting The practice of placing panels of large mesh net in the water column to catch fish, the size of which depend on the mesh size; fish that cannot pass all the way through the gillnet are ensnared by their gill covers when trying to retreat.
gravitational potential energy The amount of potential energy an object contains due to its mass and height above a reference point, such as Earth’s surface.
greenhouse effect The absorbing and reradiating of infrared light by various components of Earth’s atmosphere, resulting in higher surface and atmospheric temperatures.
gross domestic product (GDP) The total market value of all the goods (e.g., manufactured articles or agricultural crops) and services (e.g., transportation and banking services) produced within the borders of a nation during some period of time. See per capita GDP.
gross primary production The total amount of organic matter produced by the primary producers in an ecosystem over some period of time, for example, per year. See net primary production.
groundwater Water found in the pore spaces in rock and sediments beneath Earth’s surface; feeds wells, springs, and desert oases, and is Earth’s second largest reservoir of freshwater.
groundwater depletion The amount of groundwater pumped from an aquifer in excess of recharge. Groundwater depletion can result in land subsidence, which reduces the capacity of an aquifer to store water and can damage buildings and other infrastructure.
habitat Where an organism usually lives (e.g., a forest, coral reef, or marsh).
habitat corridor A strip of suitable habitat linking protected areas intended to increase the movement of wildlife between protected areas to sustain genetic variation and reduce the likelihood of extinction of protected populations.
habitat fragmentation A subdivision of a formerly continuous habitat into isolated habitat patches as a result of activities such as deforestation, road building, and dam construction on rivers.
half-
hazardous waste A flammable, reactive, corrosive, or toxic waste capable of causing illness, death, or other harm to humans and other organisms.
herbivore (primary consumer) A consumer whose diet consists entirely of plants or other primary producers, for instance, an elephant or a grasshopper.
heterotroph An organism, incapable of producing its own food, that meets its energetic and nutritional needs by feeding on organic matter produced by plants and other primary producers or on other heterotrophs. See consumer.
high-
Human Development Index (HDI) An index of national development that includes life expectancy at birth, educational opportunities, and economic productivity.
hydrocarbon An organic molecule made up of carbon and hydrogen only; the simplest hydrocarbon is methane (CH4), the main component of natural gas.
hydroelectric power Electricity generated by tapping the energy of water being driven downhill under the force of gravity.
hydrokinetic power A form of hydropower in which power stations use the kinetic energy of waves, tidal currents, or river flow to generate electricity.
hydrologic cycle The movement of Earth’s water between the oceans, atmosphere, and terrestrial and freshwater environments.
hyperaccumulators Plants that accumulate heavy metals in their tissue.
hypothesis An explanation of an observation, or a set of relationships, based on a limited amount of information; hypotheses are used to guide scientific experiments, observation, and modeling.
igneous rock Rock formed as molten rock cools and solidifies.
immigration The movement of individuals into an area, or country, to which they are not native.
indicator species A species that provides information about the state of the ecosystem in which it lives.
individual transferable quota (ITQ) (catch shares) A guaranteed right to a certain portion (quota) of the catch in a fishery or exclusive rights to certain fishing grounds; may also be granted to a fisheries cooperative or community.
indoor air pollution A serious threat to human health resulting from the buildup of pollutants in the indoor environment.
industrial fishermen Commercial fishers who may travel for weeks at a time and use expensive, technologically advanced gear to process and refrigerate or freeze their catch on board.
instream uses Benefits, such as dilution of sewage and recreational fishing and boating, that result from water flowing in river or stream channels.
integrated multi-
Integrated Pest Management (IPM) An approach to managing pests (e.g., insects, pathogens, weeds) that incorporates multiple sources of information to contain pest damage within acceptable limits while trying to minimize harm to people, property, and the environment.
integrated waste management A management strategy that minimizes waste disposal by stressing the importance of reducing waste, reusing materials, recycling, composting, and recovering energy from waste materials.
intercropping Growing two or more crops in the same field.
internal combustion engine Engine (most commonly used in cars, boats, and jet airplanes) in which combustion directly drives a set of pistons or turbines hooked up to a crank arm.
interspecific competition Competition among individuals of different species.
G-
intraspecific competition Competition among individuals of the same species.
invasive species An introduced species that poses a serious threat to native populations.
ion An atom, or group of atoms, with a net positive or negative charge (e.g., chloride, Cl–, and sodium, Na+, ions).
ionic bond A chemical bond involving the attraction between two oppositely charged ions.
irrigation A system for artificially delivering water to crops so that they can grow in areas with too little precipitation to support them otherwise.
J-
kerogen A waxy substance found in shale and other sedimentary rocks that yields oil when heated; occurs during an intermediate stage of petroleum formation.
keystone species A species with substantial influence on community structure, despite its low biomass or numbers relative to other species; the influence of keystone species is often exerted through feeding activities.
kinetic energy The energy of a moving object, which is equal to one-
K-
laboratory experiments Experiments in which scientists attempt to control, or keep constant, all factors that may influence their study system, while they vary the factor of interest and observe the effect of the variation on the study system.
Lacey Act First passed in 1900 and amended in 2008, this law forbids trade in illegally harvested plants and animals.
land ethic An ecocentric system of environmental ethics proposed by Aldo Leopold to promote the integrity, stability, and beauty of the biological community.
La Niña A period of lower than average sea surface temperatures and higher barometric pressures in the eastern Pacific Ocean, resulting in reduced storm activity in the eastern Pacific Ocean.
leachate Water that has seeped down through the waste in a landfill; flows to a sump in a modern landfill, where it can be pumped out and treated.
life cycle assessment (LCA) An estimate of the total environmental impact of a product or technology as a result of activities such as extraction of an energy source (e.g., coal), transport, processing of raw materials, construction, maintenance, dismantling, removal, and recycling or disposal of structures.
life expectancy at birth The predicted average life span of individuals born during a particular year.
life history Characteristics of a species, such as the age at which individuals begin reproducing, the number of offspring they produce, and the rate at which the young survive.
lipids Organic molecules composed of long chains of carbon atoms bonded mainly to hydrogen (e.g., fats, oils, or waxes); important component of cell membranes; function as energy storage molecules in animals and plants.
lithosphere The uppermost layer of the upper mantle above the asthenosphere, consisting of rigid, relatively brittle rocks.
loam A soil consisting of approximately equal proportions of sand, silt, and clay.
longline fishing The practice of laying out a very long line with hundreds or thousands of baited hooks; used to catch tuna (near the surface) or groundfish (e.g., halibut, cod).
low-
malaria A disease transmitted by mosquitoes that results from infection by a protozoan parasite of the genus Plasmodium; its life cycle uses two hosts: mosquitoes and humans.
mantle The layer of Earth between the crust and the core; represents the largest portion of Earth’s volume and consists of higher-
marine protected areas (MPAs) Protected areas in coastal regions and the oceans that help conserve ecosystems critical for biodiversity (e.g., coral reefs and salt marshes) and sustain populations that supply fish and other marine resources.
market-
market economy An economy in which decisions about the production and consumption of goods and services are not centralized but made by businesses and individuals, generally acting in their own self-
market failure A situation in which free markets do not allocate goods and services efficiently, such as when the price of a product does not include its environmental impact.
mass extinction A period wherein a large proportion of species becomes extinct within a few million years or less.
matter Anything that occupies space and has mass; matter exists in three main physical states: as a solid, liquid, or gas.
maximum sustainable yield (MSY) The maximum harvest of a renewable natural resource that does not reduce future yields (e.g., the sustainable annual catch from a fish population).
metamorphic rock Rock formed when any type of rock changes as it is subjected to heat and pressure.
Milankovitch Cycles Cyclic changes in the shape of Earth’s orbit, tilt in its axis, and precession of the equinoxes that produce variation in Earth’s climate.
models In science, simplified representations of a system, constructed on a scale more convenient for study than the actual system of interest.
moderator A substance (most commonly pressurized water) used in a nuclear reactor to reduce the speed at which neutrons travel.
molecule Two or more atoms held together by chemical bonds; the constituent atoms may be of the same or different elements.
money A medium of exchange using coins or paper bills.
monoculture A planting of a single variety of crop, generally over a large area, that creates an attractive target for pests and pathogens of the crop.
G-
mountaintop removal mining An extremely destructive coal mining practice that involves clear-
MRSA (methicillin-
mulch A natural or synthetic covering to the soil surface that conserves moisture, reduces soil temperature variation, and decreases growth of weeds.
municipal solid waste (MSW) Solid waste from institutions, households, and businesses, including paper, packaging, food scraps, glass, metal, textiles and other solid discards.
mutation A change in the structure of an organism’s DNA, i.e., in its genes.
mutualism Mutually beneficial relationship between organisms.
natural capital The value of the world’s natural assets (e.g., minerals, air, water, and living organisms).
natural enemies Predators and pathogens that attack herbivorous insects and other pest organisms.
natural selection A process of interaction between organisms and their environment that results in different rates of reproduction by individuals in the population with different physical, behavioral, or physiological characteristics; can change the relative frequencies of particular genes in the population—
negative feedback An increase in some factor in a system, such as a climate system, produces a decrease in that factor within the system.
net primary production The net production of organic matter by the primary producers in an ecosystem, that is, gross primary production less the organic matter used by primary producers to meet their own energy needs. See gross primary production.
neurotoxins Toxic substances that attack nerve cells.
neutron A subatomic particle, found in the nucleus of atoms, that has a mass approximately equal to that of a proton but no electrical charge.
niche A description of the physical and biological requirements of a species.
nitrification The conversion of ammonia or ammonium to nitrites (NO2–) and nitrates (NO3–) by nitrifying bacteria.
nitrogen assimilation The incorporation by plants of nitrate and ammonium into essential nitrogen-
nitrogen cycle The process whereby nitrogen passes through and between ecosystems, involving several key actions by microorganisms, including nitrogen fixation, decomposition, ammonification, nitrification, and denitrification.
nitrogen fixation Incorporation of atmospheric nitrogen, N2, into nitrogen-
non-
nonpoint sources of pollution Diffuse, and sometimes mobile, sources of pollution (e.g., runoff from an industrial, municipal, or agricultural landscape or the exhaust from automobiles).
nonrenewable energy Sources of energy, including coal, petroleum, natural gas, and nuclear fuels, that are not renewable on timescales meaningful to human lifetimes and that can be depleted with continued use.
nonrenewable resources Natural resources, such as fossil fuels, that exist in a limited supply and are not renewed on timescales meaningful to humans.
no-
nuclear energy A form of energy released when the nucleus of an atom breaks apart (nuclear fission), or when the nuclei of two atoms fuse (nuclear fusion).
nuclear fission A process in which the bonds holding the protons and neutrons that make up the nucleus of an atom are broken, resulting in the release of a large quantity of energy.
nuclear fusion A process in which the nuclei of two atoms fuse to form a new type of atom, releasing large amounts of energy.
nucleus The massive central core of an atom, which is made up of protons and neutrons, around which the atom’s electrons move.
observation Qualitative or quantitative information gathered systematically from the natural world.
O horizon The surface layer of many soils, which is rich in organic matter and a site of active decomposition.
omnivore A consumer that eats both plant and animal material.
open access A property for which there are no restrictions about who may enter and exploit its resources.
overburden The layer of rock overlying a mineral deposit (e.g., coal).
oxbow lake A crescent-
ozone A molecule made up of three oxygen atoms; considered a pollutant in the lower atmosphere, but in the upper atmosphere it shields against potentially harmful rays from the Sun.
pandemic Expansion of a disease affecting a large proportion of a population in a very large geographic area (e.g., across an entire continent).
parasite An organism that lives in or on another organism, called the host; hosts are harmed by the parasite, while the parasite receives various benefits from the host (e.g., food, protection, dispersal of offspring).
parent material The bedrock or unconsolidated deposits, such as windblown sand or silt, from which soil develops.
pathogen An organism that produces illness.
peer review As part of the process of publishing scientific papers, experts in the field of research covered by a prospective scientific paper review the research prior to publication; they check for soundness of the methods, analyses, results, and coverage of the relevant prior publications on the subject.
per capita GDP The market value of the goods (e.g., manufactured articles or agricultural crops) and services (e.g., transportation and banking services) produced within the borders of a nation per individual in its population.
persistent organic pollutants (POPs) Organic chemicals (e.g., PCBs) that remain in the environment indefinitely; can biomagnify through the food web and pose a threat to human health and the environment.
pesticide Generally a chemical substance used to kill destructive organisms, including insects (insecticide), fungi (fungicide), weeds (herbicide), and rodents (rodenticide).
G-
pesticide resistance An evolved tolerance to a pesticide by a pest population as a result of repeated exposure to a pesticide, ultimately rendering the chemical ineffective.
petroleum (crude oil) A mixture of hydrocarbons contained in sedimentary rocks of marine origin; developed from the accumulated remains of algae and zooplankton deposited on the sea floor over millions of years.
pH An indicator of the relative hydrogen ion concentration of a solution. A pH of 7 indicates a neutral solution; a pH of less than 7 is acidic (elevated hydrogen ion concentration); a pH greater than 7 is basic (reduced hydrogen ion concentration).
photoelectric effect The ejection of electrons from a substance (e.g., a metal or semiconductor) in response to stimulation by light energy.
photosynthesis A biochemical process employed by green plants, algae, and some bacteria that uses solar energy to convert water and carbon dioxide into the chemical energy in a simple sugar called glucose.
phytoremediation Bioremediation using plants to clean up contaminated sediments or soils. See bioremediation.
pioneer community The earliest community to develop during succession.
plate tectonics A theory proposing that Earth’s surface is divided into plates that move on the upper layer of the mantle; explains Earth structure and processes, including the formation of ocean basins, continents, and the geographic distribution of earthquakes and volcanic activity.
point sources of pollution Clear-
pollutant A substance (e.g., oil, pesticides) or physical condition (e.g., excessive noise) harmful to living organisms that contaminates air, water, or soil.
pollution Contamination of the environment, generally of air, water, or soil, by substances or conditions (e.g., noise, light) at levels harmful to living organisms; generally a result of human activity but may result from natural processes (e.g., wildfires, volcanic eruptions).
polyculture The growing of multiple domesticated crops that may be intermixed with useful wild species.
population density The number of individuals in a population per unit area.
population doubling time The amount of time required for a population, growing at a particular rate, to double its size.
population ecology Branch of ecology that is concerned with the factors influencing the structure and dynamics of populations, including population size, distribution, and growth.
population momentum Population growth as a consequence of a large number of women reaching childbearing age.
populations All the individuals of a species that inhabit a particular place at the same time.
positive feedback A stimulus in which an increase in some factor in a system, such as an economic system or ecosystem, produces additional increases in that factor within the system or in which a decrease in a factor causes additional decreases.
potential energy The amount of energy an object has due to the configuration of its parts (e.g., a loaded spring), its chemical makeup, or its position in a force field (e.g., Earth’s gravitational field).
pot-
precautionary principle A principle advising that precautionary measures should be taken to protect human or environmental health, even if some cause-
precession of the equinoxes Slow drift in the position in Earth’s orbit at which the equinoxes occur, a cycle repeating itself approximately every 26,000 years.
preservation ethic An environmental ethic emphasizing the protection of natural ecosystems in their original unspoiled states.
prevailing winds Winds that blow consistently from one direction (e.g., the northeast trade winds blow from the northeast).
primary energy A form of energy that requires only extraction or capture for use (e.g., coal, crude oil, wind).
primary pollutant A substance that is harmful when released into the environment (e.g., carbon monoxide, crude oil).
primary producer (autotroph) An organism, generally a plant or alga, that converts the radiant energy in sunlight to the chemical energy in sugars through the process of photosynthesis.
primary succession Succession on a bare geologic surface, such as a recent lava flow.
private property Property owned by individuals.
protected area A geographically defined area designated or regulated and managed to achieve particular conservation objectives (e.g., national parks, national forests, wildlife refuges).
proteins Long chains of amino acids (i.e., molecules consisting mainly of carbon, nitrogen, hydrogen, and oxygen) that control rates of chemical reactions, provide structural support, and perform many other functions.
proton A subatomic particle, found in the nucleus of atoms, that has a positive charge (+1) and atomic mass of 1.
radiant energy The energy of electromagnetic radiation, including visible light, infrared light, ultraviolet light, microwaves, radio waves, or X-
ranching The practice of raising domesticated livestock for meat, leather, wool, and other products.
reactive Chemically responsive; a reactive substance will readily undergo a violent chemical change when in contact with other substances.
reclamation A process that restores an ecosystem to its natural structure and functioning prior to mining or to an economically usable state.
recycling The process of returning raw materials in waste (e.g., glass, plastics, metal, paper) to the manufacturer for reuse.
renewable energy Sources of energy, including solar, wind, hydrologic, geothermal, and biomass, that can be replenished in a relatively short period of time. Use does not deplete renewable energy sources.
renewable resources Natural resources, such as wood, forage, or fish, that are replaced through natural processes on relatively short timescales and thus can last indefinitely under careful management.
replacement-
reservoir A body of water, ranging in size from a pond to an ocean, including below-
Resource Conservation and Recovery Act (RCRA) A law passed by the U.S. Congress that banned open dumping of wastes and set standards for solid waste landfills.
G-
resource partitioning Coexisting species use different resources, such as food, nesting sites, and feeding areas.
reverse osmosis A desalination process that uses selectively permeable membranes and pressure to separate salts and water.
R horizon The base of a soil profile composed of consolidated bedrock, immediately below the C horizon.
riparian The transition zone between a river or stream and the terrestrial environment, generally inhabited by a biological community distinctive from adjacent aquatic and upland communities. Riparian zones naturally flood periodically and usually have shallow water tables.
risk The chance of harmful effects to human health or to ecological systems resulting from exposure to any physical, chemical, or biological agent.
risk characterization A qualitative or quantitative estimate of the likelihood that hazards associated with an agent of concern will negatively impact an exposed population.
rock A natural, solid, inorganic substance formed from one or more minerals.
rock cycle Geologic processes that convert each of the three major rock types (igneous, sedimentary, and metamorphic) into one of the other types.
r-
runoff The amount of water falling as precipitation that flows off the land as surface and subsurface flow.
run-
salinization The process of salt buildup in a soil.
sanitary landfill A solid waste disposal site consisting of a lined pit constructed and managed in ways to minimize environmental impacts.
saturated zone The layers of rock below the water table, in which the pore spaces in the geologic formation are saturated with water.
science A formal process used to study nature, and the body of knowledge resulting from that process.
seawater Ocean water and the water of seas, such as the Caribbean and Mediterranean seas. The salinity of seawater averages about 34,000 mg/l (34 g/l), but ranges from 30,000 to about 40,000 mg/l (30 to 40 g/l).
second law of thermodynamics With each energy transformation, or transfer, the amount of energy in a system available to do work decreases. In other words, the quality of the energy declines with each energy transfer or transformation. See first law of thermodynamics.
secondary pollutant A pollutant formed from the chemical reactions between other pollutants (e.g., ozone in the lower atmosphere).
secondary (consumer) production The amount of consumer biomass, or energy, that goes into growth and reproduction, analogous to net primary production by photosynthetic organisms.
secondary succession Succession following disturbance of an established community that doesn’t destroy all living creatures or the soil.
sedimentary rock Rock formed either as rock fragments deposited by water, wind, or ice are cemented together and solidify or as rock forms through chemical precipitation.
selective logging The clearing of land for lumber that focuses on the most mature, high-
semiconductor A material that conducts current, but only somewhat, because its properties lie somewhere between those of an insulator and a conductor.
sex ratio at birth The ratio of male to female newborns.
shelterwood harvesting Removes the tallest trees in a series of partial cuts, leaving behind enough of a forest canopy to provide shelter for speedy regrowth of shade-
sick building syndrome A circumstance in which many building occupants experience symptoms of illness (e.g., headaches, respiratory and eye irritation, nausea) for which no specific cause has been identified.
skimmer A device used to collect spilled oil from the water’s surface.
slash-
small-
soil texture The relative fineness or coarseness of a soil, which is determined by its proportions of sand, silt, and clay.
solubility The amount of a substance capable of dissolving in a particular amount of solvent.
source reduction A waste management tactic aimed at reducing the amount of material that enters the waste stream.
speciation An evolutionary process by which new species arise.
species A group of interbreeding, or potentially interbreeding, populations, reproductively isolated from other populations.
species diversity A measure of diversity that combines the number of species in a community and their relative abundances.
species evenness How evenly individuals are apportioned among the species inhabiting a community; higher evenness increases species diversity.
species richness The number of species in a community or living in a local area or region; higher species richness increases species diversity.
sport (recreational) fishing The practice of fishing for pleasure (e.g., fly-
S-
state property Property owned by federal, state, or local governments.
stratosphere The layer of Earth’s atmosphere beginning at an elevation of 10 kilometers and extending outward to 50 kilometers (6.2 to 31.1 miles) above sea level.
strip mining A coal extraction technique in which overburden is removed from a long strip of land, exposing a coal seam; once the coal is removed, material from an adjacent strip is used to fill the excavation.
stock A discrete subpopulation of a species, which is reproductively isolated from other stocks.
stock assessment Estimated size of a fish stock, the rate at which the population is growing, and the rate of harvest.
subduction Process in which one tectonic plate moves under another, generally occurring where oceanic plates, which are of higher density, collide with continental plates.
subduction zone Zone where oceanic plates and continental plates collide, forming deep sea trenches and active volcanoes along the continental margin.
subsidence A settling or sudden sinking, in the case of sinkhole formation, of a land surface as a result of processes such as groundwater withdrawal or loss of organic matter in soil.
G-
subsistence economy An economy in which individuals or groups produce or harvest enough resources to largely support themselves, with fewer resources gained through purchase or trade with other groups.
subsistence fishing The practice of catching enough fish for one’s family plus a bit more for bartering or selling.
succession The gradual change in a community over time following a disturbance.
supply and demand An economic model stating that the price of a good (or service) will reach equilibrium when the consumer demand for it at a certain price equals the quantity supplied by producers.
sustainability The wise use of resources to ensure our ability to endure and live healthy lives, without compromising the welfare of future generations.
sustainable development A process of development that meets the needs of the present generation without reducing the ability of future generations to meet their needs. Development is sustainable when it does not, at a minimum, endanger Earth’s natural life support system, including the atmosphere, waters, soils, and biological diversity.
sympatric speciation A process by which new species arise without geographic isolation.
synergistic effect An interaction of two toxic substances wherein their combined toxicity is greater than the sum of their individual effects.
take back laws State regulations that require manufacturers of various electronics to pay for e-
Taq polymerase An enzyme isolated from a bacterium discovered living in hot springs in Yellowstone National Park; used to amplify small quantities of DNA.
technology Practical application of scientific knowledge and methods to create products and processes.
teratogen A substance that causes abnormalities during embryonic growth and development, resulting in birth defects.
terra preta Dark, fertile soils high in charcoal and nutrient content, created by native populations in the Amazon River Basin before the arrival of Europeans.
terrestrial harvest systems Ways of extracting production from ecosystems, ranging from hunting and gathering in unmanaged natural ecosystems to nomadic herding and small-
tertiary treatment Advanced treatment of wastewater, which follows primary and secondary treatment, that removes dissolved organic chemicals, nitrogen, phosphorus, several other dissolved salts, and pathogens.
theory A scientific hypothesis that has withstood sufficient testing—
thermal (heat) energy A form of kinetic energy due to molecular motion in a mass of a substance, such as a mass of steam.
threshold dose The lowest dose (concentration) of a toxic substance that induces a toxicity response in an organism.
total fertility rate An estimate of the average number of children that a woman in a population gives birth to during her lifetime.
toxic Poisonous; a toxic substance is harmful to living organisms in relatively low amounts.
toxicant A toxic substance produced by humans or as a by-
toxicology The science concerned with the effects of toxic substances on humans and other organisms.
toxin A poisonous substance produced by a living organism (e.g., a plant, animal, fungus, or bacterium) that can harm human health. See toxicant.
transboundary pollution The transport of pollutants by wind and water around the biosphere, across geographical and political borders.
transgenic organism A GM organism that contains genes from another species.
trophic level A step in the movement of materials or energy through an ecosystem or the position of a species in a food web.
ultraviolet (UV) light Shorter-
umbrella species A species whose protection provides protection for the entire ecosystem on which that species depends.
unsaturated zone The layers above the water table, which are not saturated with water.
upwelling The movement of cold subsurface water to the ocean’s surface when warmer surface waters move offshore under the influence of prevailing or seasonal winds.
vector An organism that transmits a pathogen or parasite to other organisms (e.g., mosquitoes transmit malaria and other diseases to humans and other species).
virus A structurally simple disease-
waste stream The flow of discarded materials, especially municipal solid waste, from institutions, homes, and businesses.
water reclamation Any process of treating wastewater to make it safe for reuse or recycling.
water recycling Using treated wastewater for beneficial purposes, including industrial processes, irrigation, recharging groundwater supplies, restoring wetlands and aquatic ecosystems, and augmenting drinking-
water table The uppermost level of groundwater, which forms the boundary between the saturated and unsaturated zones.
waterlogged soil A condition in which the water table is at or near the soil surface.
watershed (catchment, drainage basin) The land area from which an aquifer or river system acquires its water; also defined as the dividing line between catchments or drainage basins.
weather Atmospheric conditions, temperature, humidity, cloud cover, rainfall, etc. at a particular place and time (e.g., conditions during a particular day or month).
weathering The fragmentation and decomposition of mineral materials as a result of chemical, biological, and mechanical processes, resulting in the release of nitrogen, phosphorus, and other elements.
work A description of the transfer of energy; the work done on an object by a force is determined by the amount of force times the distance the object moves in the direction of the force. See energy.
zoonotic disease Any infectious disease that can spread from animals to humans.
G-