GLOSSARY

The following is the glossary as it appears in Our Environment: A Canadian Perspective, 2nd edition.  Select the letters to jump to that particular section.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

abiotic. The nonliving components of an ecosystem such as water, air, solar energy, and nutrients necessary to support life in a given area. Compare biotic.

acclimation. The adjustment of a species to slowly changing conditions in an ecosystem, such as temperature. See also threshold effect.

adaptation. Any genetically controlled characteristic—structural, physiological, or behavioural—that enhances the chance for members of a population to survive and reproduce in its environment. See also mutation.

aerobic respiration. A complex chemical process that drives the life processes of living things, by using oxygen to convert nutrients such as glucose back into carbon dioxide and water. The opposite of photosynthesis.

aesthetic arguments. A rationale for the conservation of nature based on its beauty and aesthetic qualities. Compare utilitarian justification, ecological justification, moral justification.

age-specific rate. The number of live births per 1000 women of a specific age group per year.

alternative energy. Renewable energy sources, such as wind, flowing water, solar energy and biomass, which create less environmental damage and pollution than fossil fuels, and offer an alternative to nonrenewable resources.

aquaculture. The breeding and raising of fish under controlled conditions, with the goal of high level production for food or recreational purposes.

atmosphere. A thin layer of gases consisting mostly of nitrogen and oxygen that completely surrounds the solid and liquid earth. See also troposphere, stratosphere.

atomic number. The number of protons in an atom's nucleus, which distinguishes it from the atoms of other elements.

atoms. The smallest particles that exhibit the unique characteristics of that particular element.

autotrophs. See producers.

B

background extinction. The continuous, low-level extinction of species that has occurred throughout much of history. Compare mass extinction.

barrier islands. Long, low, offshore islands of sediment that run parallel to much of North America's Atlantic and Gulf coasts and help protect coastal wetlands and habitats from storm damage.

bellwether species. See indicator species.

benthic environment. The ocean floor, one of the two main divisions of the open sea environment. See also pelagic environment.

biodiversity. The diversity of life on earth, consisting of genetic diversity, species diversity and ecosystem diversity.

biofuels. See ethanol.

biogeochemical cycles. See nutrient cycles.

biological evolution. The change in inherited characteristics of a population from generation to successive generation.

biological oxygen demand (BOD). The amount of oxygen needed during the time it takes for waste material to be oxidized. Water quality is directly affected by this; some organisms thrive on a higher BOD and some suffocate for lack of oxygen.

biomagnification. The accumulation and concentration of certain substances in organisms, such as chlorinated organic compounds (DDT and PCBs) in the fatty tissues of predators in the Arctic marine system.

biomass. The amount of living or organic matter contained in living organisms.

biome. A broad, regional type of ecosystem characterized by distinctive climate and soil conditions and a distinctive biological community adapted to those conditions.

biosphere. That part of the earth inhabited by plants and animals, and their interactions with the atmosphere, hydrosphere, and lithosphere.

biotic potential. The maximum rate a population can increase under ideal conditions.

biotic. The living components of an ecosystem including plants, animals, and their products (secretions, wastes, and remains) and effects in a given area. Compare abiotic.

bitumen. A black oil rich in sulphur that is found in oilsand. It can be treated and chemically upgraded into synthetic crude oil, though the net useful energy yield is lower than for conventional oil because more energy is required to extract and process it. See also oilsand.

C

carnivores. Organisms that feed indirectly on plants by eating the meat of herbivores. Most carnivores are animals, but a few examples are in the plant kingdom, such as the Venus flytrap. See also herbivores, omnivores.

carrying capacity. The number of organisms that an ecosystem can support indefinitely, while maintaining its productivity, adaptability, and capability for renewal.

chemical change. A change in which a chemical reaction is produced and a new substance created, as when gasoline is burned to produce carbon dioxide. Compare physical change.

chemotrophs. Producers, including algae and bacteria, which convert the energy found in inorganic chemical compounds into more complex energy, without the use of sunlight. See also producers, consumers.

clear-cutting. A system of tree harvesting that removes all the trees in a given area, as opposed to selective cutting that leaves some trees standing. Replanting after clear-cutting can be difficult.

climax community. The mature stage of succession in a particular area, in which all organisms and nonliving factors are in balance.

co-generation. The production of two useful forms of energy from the same source, such as heat and power. See also district heating.

coal. The most abundant fossil fuel in the world, with reserves four to five times that of oil and gas combined. It has a relatively high net useful energy yield and is highly effective for providing industrial heat.

coastal wetlands. Coastal area that provides breeding grounds and habitats for many marine organisms as well as for waterfowl, shorebirds, and other wildlife.

coastal zone. The area where the ocean meets the land, which constitutes 10 percent of the ocean's area but contains 90 percent of all marine species.

commensalism. An interaction between species in which one benefits and the other is neither helped nor harmed. See also mutualism, symbiosis.

community. An area where different species interact, such as an alpine community or a prairie community. See also habitat.

competitive exclusion principle. When two species are competing for the same resources, one must migrate to another area, if possible, shift its feeding habits or behaviour, suffer a sharp decline in population numbers, or become extinct.

compounds. One of the basic forms of chemical composition, which involves two or more different elements held together in fixed proportions by the attraction in the chemical bonds between their constituent atoms. See also mixtures, elements.

consumers. Those organisms that eat the cells, tissues, or waste products of other organisms. Animals are common consumers. See also producers, chemotrophs.

controlled experiment. An experiment designed to test the effects of independent variables on a dependent variable by changing one independent variable at a time.

coral reefs. Found in warm tropical and subtropical oceans, these formations are rich in life and may contain more than 3000 species of corals, fish, and shellfish.

country food. Food grown by people in small communities living in harmony with their local environment.

crude birth rate. The annual number of live births per 1000 population, without regard to age or sex composition.

crude death rate. The annual number of deaths per 1000 population.

crude growth rate. The net change, or difference, between the crude birth rate and the crude death rate.

D

decomposer. See microconsumers.

deductive reasoning. Drawing conclusions from observations of the natural world by means of logical reasoning. Compare inductive reasoning.

deforestation. To clear an area of forests or trees, usually for commercial use of the lumber or agricultural use of the land.

demographic transition. A four-stage model of population change that links industrial development with zero population growth, and suggests a post industrial phase that would focus more on sustainable forms of economic development.

demographic trap. A state in which a nation or population is stuck in the second stage of demographic transition, with a low death rate, a high birth rate, and increasing demand on available resources.

demography. The study of the characteristics and changes in the size and structure of human populations.

dependency ratio. A measure of the number of dependents, young and old, that each 100 people in their economically productive years must support. It is used to forecast the condition of the future human population.

detritus feeders. See detritivores.

detritivores. Consumers that ingest fragments of dead organic material. Examples are earthworms and maggots.

differential reproduction. The ability to produce more offspring with the same favourable adaptations as the parents, which will allow them to survive under changed environmental conditions.

dissolved oxygen content. The amount of oxygen dissolved in a given volume of water at a particular temperature and pressure. This can be a limiting factor on the growth of aquatic populations.

district heating. An effort to maximize energy efficiency in power generating stations, which involves a steam cycle that is modified so that the steam is extracted and used to produce hot water. The water is then pumped through pipes to surrounding buildings to supply heat. See also co-generation.

doubling time. The length of time required for a population to double in size.

E

ecological diversity. The variety of biological communities, such as forests, deserts, grasslands, and streams, that interact with one another and with their physical and chemical (nonliving) environments. See also species diversity.

ecological footprint. A link between human lifestyles and ecosystems, which allows people to visualize the impact of their consumption patterns and activities on ecosystems.

ecological justification. A rationale for the conservation of nature based on the idea that the environment provides specific functions necessary to the persistence of our life. Compare utilitarian justification, aesthetic arguments, moral justification.

ecological niche. The role an organism plays within the structure and functions of an ecosystem, and the way it interacts with other living things and with its physical environment.

ecology. The study of the interactions of living organisms with one another and with their nonliving environment of matter and energy.

ecosphere. See biosphere.

ecosystem. A community and its members interacting with each other and their nonliving environment.

electrons. Negatively charged ions that continually orbit the nucleus of an atom and are held in orbit by attraction to the positive charge of the nucleus. See also protons, neutrons.

elements. One of the basic forms of chemical composition. All matter is built from the 109 known chemical elements; these are the simplest building blocks of all matter. See also compounds, mixtures.

emissions permits. A strategy developed to reduce greenhouse gas emissions, where companies buy and sell from each other the right to release greenhouse gases.

endemic species. A species that is native to a particular geographic region.

energy quality. The measure of an energy source's ability to perform useful work, such as running electrical devices or motors. See also high-quality energy, low-quality energy.

energy. The ability or capacity to do work. Energy enables us to move matter and change it from one form to another.

environment. The surroundings in which plants and animals live, affected by various physical factors such as temperature, water, light, and food resources.

environmental ethics. A new discipline that analyzes the issues regarding our moral obligations to future generations with respect to the environment.

environmental impact assessment (EIA). A process that aims to provide decision makers with scientifically researched and documented evidence to identify the likely consequences of undertaking new developments and changing natural systems. See also environmental impact statement.

environmental impact statement (EIS). A key component of an environmental impact assessment, an EIS provides a nontechnical summary of the study, including the main project characteristics, aspects of the environment likely to be affected, possible alternatives, and suggested measures and systems to monitor or reduce any harmful effects. See also environmental impact assessment.

environmental resistance. The limits set by the environment that prevent organisms from reproducing indefinitely at an exponential rate.

estuaries. A body of coastal water partly surrounded by water, with access to the open sea and a large supply of fresh water from rivers. These conditions provide excellent conditions for many important shellfish and fin fish species.

ethanol. A fuel converted from biomass materials and used to power motor vehicles, either directly as fuel or as an octane-enhancing gasoline additive. Ethanol can reduce carbon monoxide emissions from regular gasoline blends.

eukaryotic. Cells with a high degree of internal organization, including a nucleus (genetic material surrounded by a membrane) and several other internal parts surrounded by membranes. See also prokaryotic.

eutrophic. A lake enriched with nutrients in excess of what is required by producers. See also oligotrophic, mesotrophic.

exclusive economic zone. An area of exclusive fishing rights granted to Canada in the 1982 United Nations Convention on the Law of the Sea. It came into force in 1994.

exponential growth. Growth in a species that takes place at a constant rate per time period.

extinction. The process whereby a species is eliminated from existence when it cannot adapt genetically and reproduce successfully under new environmental conditions. See also mass extinction, background extinction.

F

fact. An observation that all (or almost all) scientists agree is correct.

first law of energy. See first law of thermodynamics.

first law of thermodynamics. During a physical or chemical change, energy is neither created nor destroyed. See also second law of thermodynamics.

food chains. The sequence of who feeds on or decomposes whom in an ecosystem.

food web. A complex network of feeding relationships in which the flow of energy and materials through an ecosystem takes place. That flow occurs on the basis of a range of food choices on the part of each organism involved.

fossil fuels. The remains of prehistoric animals, forests, and sea floor life that have become buried in layers of sediment and decomposed very slowly, eventually being converted into crude oil. See also hydrocarbons.

fundamental niches. The full range of physical, chemical, and biological factors each species could use if there were no competition from other species. See also interspecific competition.

G

gene pool. The sum of all genes possessed by the individuals of a population.

general fertility rate. The number of live births per 1000 women of childbearing age per year.

generalist species. The ability to live in many different places while tolerating a wide range of environmental conditions. Humans are considered a generalist species. See also specialist species.

genes. Segments of various deoxyribonucleic acid (DNA) molecules found in chromosomes. Genes impart certain inheritable traits to organisms.

genetic diversity. The diversity within a given population that shares common structural, functional, and behavioural traits but varies slightly in genetic makeup and so exhibits slightly different behaviours and appearances.

global warming potential. A concept developed to take into account the differing times that gases remain in the atmosphere, in order to evaluate the potential climate effects of equal emissions of each of the greenhouse gases.

gross primary productivity. The rate at which producers in an ecosystem capture and store chemical energy as biomass. Compare net primary productivity.

groundwater. Water that has accumulated beneath the Earth's surface in cracks, the pores of rocks, and other spaces. It can reach down from above or rise up from below. Compare surface water.

H

habitat. The place where an organism or population lives, such as an ocean, a forest or a stream. See also community.

heat island. A microclimate in which the air temperature is slightly higher than in the surrounding area. In an urban heat island, for example, the temperature in the city is 1-2°C higher than in the rural area around it.

herbivores. Organisms that eat green plants directly as a source of nutrients. Deer are common herbivores. See also carnivores, omnivores.

heterotrophs. See consumers.

high-quality energy. Concentrated energy sources such as electricity, gasoline, and food, which enable people and machines to perform useful tasks. See also low-quality energy, energy quality.

high-quality matter. Material such as coal or salt deposits commonly found near the Earth's surface in an organized or concentrated form, so that its potential for use as a resource is great. See low-quality matter.

highgrading. An unsound practice associated with selective cutting techniques that involves logging the highest-quality and most accessible timber first.

human cultural diversity. The variety of human cultures that represent our adaptability and survival options in the face of changing conditions.

hydrocarbons. Any of a class of compounds containing only hydrogen and carbon, which include fossil fuels. See also fossil fuels.

hydroelectric power. Electrical power generated from the energy of falling water or any other hydraulic source.

hydrogen power. A source of energy that converts hydrogen to electricity to provide heat, light, and power. Though hydrogen is readily available, the production of hydrogen power is expensive and not yet commercially viable.

hydrological cycle. The movement of water between the atmosphere and the oceans, through evaporation, runoff from streams and rivers, and precipitation.

hydrosphere. The Earth's supply of moisture in all its forms: liquid, frozen, and gaseous. This includes surface water, underground water, frozen water, water vapour in the atmosphere, and moisture in the tissues and organs of living things.

hypothesis. An explanation that is based on testable observations and experiments, and that can be accepted until it is disproved.

I

igneous rock. Rock formed from molten materials crystallizing at the Earth's surface (such as lava from volcanoes), or beneath the surface (such as granite). See also sedimentary rock, metamorphic rock.

immigrant species. Those species that migrate into or are introduced into an ecosystem, deliberately or accidentally, by humans.

independent variable. A condition that is deliberately manipulated by scientists to test the response in an experiment. See also responding variable, operational definitions.

indicator species. Those species that provide early warnings of environmental damage to communities or ecosystems.

inductive reasoning. Drawing a general conclusion based on a limited set of observations. Compare deductive reasoning.

infant mortality rate. The ratio of deaths of infants under 12 months per 1000 live births.

inferences. Conclusions derived either by logical reasoning from premises and/or evidence, or by insight or analogy based on evidence.

instream uses. Water used in its natural setting for hydroelectric power, transportation, fisheries, and other applications. See also withdrawal uses.

interspecific competition. Competition from other species for one or more of the same limited resources of food, sunlight, water, soil, nutrients, or space. See also fundamental niches.

intrinsic value. A value placed on the inherent qualities of a species, independent of its value to humans.

invertebrates. Animals without backbones, such as jellyfish, worms, insects, and spiders. Compare vertebrates.

ions. Subatomic, electrically charged particles in an atom. See also protons, neutrons.

J

K

keystone species. Those species that play a crucial role in helping to maintain the ecosystems of which they are a part, by pollination, regulation of populations, or other activities.

kinetic energy. Energy associated with the movement of matter and mass. A moving air mass such as wind has kinetic energy, as do flowing streams, moving cars, heat, and electricity. See also potential energy.

L

law of conservation of matter. Matter is neither created nor destroyed, but is combined and rearranged in different ways.

law of tolerance. The presence, number, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by the species. See also limiting factor principle.

limiting factor principle. Too much or too little of any abiotic factor can limit or prevent growth of a population even if all other factors are at or near the optimum range of tolerance. See also law of tolerance.

limnetic zone. The open water area away from the shore of a lake or pond, with less light penetration and fewer producers. See also littoral zone, profundal zone.

lithosphere. The upper zone of the Earth's mantle and the inorganic mixture of rocks and mineral matter in the Earth's crust.

littoral zone. The shallow water and vegetated area along the shore of a lake or pond, and the most productive zone of the lake. See also limnetic zone, profundal zone.

logistic growth curve. The idea that the population increases exponentially at the outset and then levels out as the carrying capacity of the environment is reached.

long-distance commuting. The practice of flying miners into a mine to work for a designated period and then flying them back to their homes in larger communities for another period.

low-quality energy. Dispersed energy, such as the heat stored in the oceans, with little capacity to perform useful tasks. See also high-quality energy, energy quality.

low-quality matter. Hard-to-reach matter, such as that dispersed or diluted in the atmosphere or oceans. See also high-quality matter.

M

macroconsumers. Organisms that feed by ingesting or engulfing particles, parts or entire bodies of other organisms, living or dead, including herbivores, carnivores, omnivores, scavengers, and detritivores.

macronutrients. The main constituents of the complex organic compounds required by all living organisms. The six major macronutrients are carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulphur. See also micronutrients.

mangrove swamp. A collection of tropical evergreen trees with stilt-like aerial roots that cause thick undergrowth and provide habitat for marine organisms, waterfowl, and other coastal species.

manipulated variable. See independent variable.

mass extinction. The disappearance of numerous species over a relatively short time. See also background extinction.

matter. Anything that has mass and takes up space, including everything that is solid, liquid, or gaseous.

mesotrophic. A lake that falls in the mid-range between the two extremes of nutrient enrichment required by producers. See also oligotrophic, eutrophic.

metamorphic rock. Formed when existing rocks lying deep below the Earth's surface are subjected to high temperatures, high pressures, chemically active fluids, or a combination of these agents, causing the rocks' crystal structure to change. See also igneous rock, sedimentary rock.

microconsumers. Organisms that live on or within their food source, completing the breakdown of complex molecules into simpler compounds (a process that we call rot or decay).

micronutrients. The trace elements of complex organic compounds required by all living organisms. These include boron, copper, zinc, and others. See also macronutrients.

milling. In the processing of minerals, the crushing and grinding of ores to separate the useful materials from the nonuseful ones. See also tailings.

mineral exploration. Finding geological, geophysical, or geochemical conditions that differ from those of their surroundings.

mineral fuels. Crude oil and equivalents, including natural gas, coal, and natural gas byproducts. In 1996, they accounted for approximately 65 percent of the total value of Canadian mineral production.

mixtures. One of the basic forms of chemical composition. A combination of elements, compounds, or both.

molecules. Particle formed when two or more atoms of the same or different elements combine.

moral justification. A rationale for the conservation of nature based on the idea that elements of the environment have a right to exist, independent of human desires. Compare utilitarian justification, moral justification, aesthetic arguments.

mutation. The random and unpredictable changes in DNA molecules that can be transmitted to offspring and produce variability. See also adaptation.

mutualism. A symbiotic relationship in which both interacting species benefit, as when honeybees pollinate flowers as they feed on the flower's nectar. See also symbiosis, commensalism.

N

native species. Those species that normally live or thrive in a particular ecosystem.

natural gas. A gaseous hydrocarbon mixture of methane combined with smaller amounts of propane and butane. The conventional or 'associated' type is located underground above most reserves of crude oil, while the nonassociated type is found on its own in dry wells.

natural selection. The tendency for only the best-adapted organisms to survive and reproduce in a given environment.

net primary productivity. The rate at which organic matter is incorporated into plant bodies so as to produce growth. See also gross primary productivity.

net useful energy. The usable amount of energy available from an energy source over its lifetime.

neutrons. Uncharged or electrically neutral ions, which cluster with protons in the centre of an atom and comprise its nucleus. See also electrons, protons, ions.

nitrogen fixation. A part of the nitrogen cycle in which atmospheric nitrogen is converted into other chemical forms available to plants.

nonrenewable resources. Resources such as coal, oil, and other fossil fuels that are finite in supply and replaced so slowly that they are soon depleted. Compare renewable resources.

nuclear energy. The energy released by reactions within atomic nuclei, such as nuclear fission or nuclear fusion. See also radioactive wastes.

nutrient cycles. The means by which the nutrient elements and their compounds cycle continually through Earth's atmosphere, hydrosphere, lithosphere, and biosphere.

nutrients. The materials that an organism must take in to enable it to live, grow, and reproduce.

O

observations. Information gathered through any of our five senses or instruments that extend these senses.

oil shale. Rock that contains a solid mixture of hydrocarbon compounds called kerogen. Once crushed and heated, kerogen vapour is condensed to form heavy, slow-flowing shale oil.

oilsand. A combination of clay, sand, water, and bitumen. Canada is home to the largest know oilsand deposits in the world. See also bitumen.

oligotrophic. A lake with minimal levels of nutrients required for producers. See eutrophic, mesotrophic.

omnivores. Consumers that eat both plants and animals, such as black bears, pigs, and humans. See also carnivores, herbivores.

operational definitions. Set of criteria that tell scientists what to look for or what to do in order to carry out the measurement, construction, or manipulation of variables. See also independent variable, responding variable.

organism. A complex organization of cells, tissues, organs, and body systems that work together to create a multicellular individual such as a bear, whale, human, or orchid.

P

parasitism. A symbiotic relationship in which the parasite benefits by obtaining nourishment from the host and the host is weakened or killed by the parasite.

pelagic environment. The ocean water, one of the two main divisions of the open sea environment. See also benthic environment.

permafrost. A permanently frozen layer of subsoil, characteristic of the tundra biome.

physical change. A change from one state to another, as when water changes from ice to its liquid state. See also chemical change.

polar stratospheric clouds. Formed in extremely cold temperatures within the polar vortex as it matures, cools, and descends, these clouds have been linked to depletion of the ozone layer.

polar vortex. An atmospheric condition that occurs during the polar winter night when the Antarctic air mass is partially isolated from the rest of the atmosphere and circulates around the pole.

polynyas. An area of unfrozen sea water, created by local water currents in northern oceans. They act as biological hotspots and serve as vital winter refuges for marine mammals.

population age structure. The distribution of the population by age, used in analysis of demographic trends.

population lag effect. See population momentum.

population momentum. When a population achieves replacement fertility, that population continues to grow for several generations before stabilizing.

population. A group of individuals of the same species living and interacting in the same geographic area at the same time.

potential energy. Energy stored and potentially available for use, such as the chemical energy stored in gasoline or food molecules. See also kinetic energy.

predation. When members of a predator species feed on parts or all of an organism of a prey species.

predator–prey relationships. The most obvious form of species interaction, which occurs when one organism (the predator) feeds on another (the prey).

predator. An organism, usually an animal, that feeds on other organisms, as when a turtle eats a fish in a freshwater pond ecosystem.

prey. The organism consumed by a predator.

primary consumer. See herbivores.

primary succession. The development of biotic communities in a previously uninhabited and barren habitat with little or no soil. Compare secondary succession.

primary treatment. The lowest level of treatment in the management of municipal wastes, which involves the mechanical removal of large solids, sediment, and some organic matter. See also secondary treatment, tertiary treatment.

principle of connectedness. Everything in the natural world is connected to and intermingled with everything else, and a change in environmental conditions will have multiple effects.

producers. Those self-nourishing organisms that perform photosynthesis by converting relatively simple inorganic substances such as water, carbon dioxide, and nutrients into complex chemicals such as carbohydrates, lipids, and proteins. Green plants and phytoplankton are common producers. See also chemotrophs, consumers.

profundal zone. The deepest zone of a lake, where lack of light means that no producers can survive. See also littoral zone, limnetic zone.

prokaryotic. Cells that lack a nuclear envelope and other internal cell membranes, including bacteria. Compare eukaryotic.

protons. Positively charged ions, which cluster with neutrons in the centre of an atom and comprise its nucleus. See also electrons, neutrons, ions.

Q

qualitative data. Non-numerical records of independent and dependent variables kept during experiments.

quantitative data. Numerical records of independent and dependent variables kept during experiments.

R

radioactive wastes. Radioactive by-products from the operation of a nuclear reactor or from the reprocessing of depleted nuclear waste. See also nuclear energy.

realized niche. That portion of a fundamental niche actually occupied by a species, which results from the sharing of resources in a given ecosystem.

renewable resources. Resources such as forests, solar energy, and fisheries that can be replaced by environmental processes in a time frame meaningful to humans. Compare nonrenewable resources.

replacement fertility. The fertility rate needed to ensure that the population remains constant as each set of parents is replaced by its offspring.

resource partitioning. The dividing of scarce resources in order that species with similar requirements can use the resources in different ways, in different places, and at different times.

responding variable. A condition that responds to changes in the independent variable in an experiment. Also referred to as a dependent variable. See also independent variable, operational definitions.

S

salinity. The amounts of various salts dissolved in a given volume of water. This can be a limiting factor on the growth of aquatic populations.

scavengers. Consumers that eat dead organic material (consuming the entire dead organism), such as vultures and hyenas.

scientific method. Systematic methods used in scientific investigations of the natural world, which include designing controlled experiments, gathering data, and developing and testing hypotheses.

second law of energy. See second law of thermodynamics.

second law of thermodynamics. With each change in form, some energy is degraded to a less useful form and given off into the surroundings, usually as low-quality heat. See also first law of thermodynamics.

secondary consumers. See carnivores.

secondary succession. The development of biotic communities in an area where the natural vegetation has been removed or destroyed but where soil is present. See also primary succession.

secondary treatment. The second level of treatment in the management of municipal wastes, which employs biological processes by which bacteria degrade most of the dissolved organics, about 30 percent of the phosphates, and about 50 percent of the nitrates. See also primary treatment, tertiary treatment.

sedimentary rock. Rock formed when small bits and pieces of matter and sediments are carried by wind or rain and then deposited, compacted, and cemented to form rock. See also igneous rock, metamorphic rock.

solar energy. Energy derived from the sun in the form of solar radiation.

specialist species. The ability to live in only one type of habitat, eat only a few types of food, or tolerate a narrow range of climatic or environmental conditions. See also generalist species.

speciation. The formation of two or more species from one as the result of divergent natural selection and response to changes in environmental conditions.

species diversity. The number of different species and the relative abundance of each in different habitats on Earth. See also ecological diversity.

species. A group of organisms that resemble one another in appearance, behaviour, chemical makeup and processes, and genetic structure, and that produce fertile offspring under natural conditions.

stewardship. The concept that mankind has an ethical responsibility to care for plants, animals, and the environment as a whole, due to our superior intellect and power to change the natural world.

stratosphere. The layer above the troposphere that contains the ozone layer and protects life on Earth's surface by absorbing most incoming solar ultraviolet radiation. See also troposphere, atmosphere.

surface water. All bodies of water, such as lakes, rivers, streams and oceans, that lie on the surface of the Earth. Compare groundwater.

sustainability. The ability of an ecosystem to maintain ecological processes, functions, biodiversity, and productivity over time. See also sustainable development.

sustainable development. Maintaining environmental resources so that they continue to provide benefits to living things and the larger environment of which they are a part. See also sustainability.

sustainable yield. The greatest productivity that can be yielded from a renewable resource without depleting the supply in a given area.

symbiosis. Any intimate relationship between two or more different species. The fur of the three-toed sloth is often occupied by algae and insects that feed on the algae. See also mutualism, commensalism.

T

tailings. The nonuseful materials removed from the mill after the recoverable minerals have been extracted in the processing of minerals. See also milling.

taxonomic. The classification of organisms according to evolutionary relationships.

tertiary consumers. Carnivores that eat other carnivorous (or secondary) consumers.

tertiary treatment. The third level of treatment in the management of municipal wastes, which involves a chemical process that removes phosphates, nitrates, and other contaminants not removed during secondary treatment. See also primary treatment, secondary treatment.

theories. Models based on currently accepted hypotheses that offer broadly conceived, logically coherent, and very well supported concepts.

threshold effect. The harmful or even fatal reaction to exceeding the tolerance limit of a species in a given ecosystem. See also law of tolerance, acclimation.

Total Allowable Catch (TAC). A limit set by the Northwest Atlantic Fisheries Organization (NAFO), an agency of the United Nations Food and Agricultural Organization, to ensure that groundfish stocks were not depleted.

total fertility rate (TFR). The average number of children expected to be born to a woman during her lifetime.

trophic level. Each organism is assigned a feeding or trophic level depending on whether it is a producer or a consumer and on what it eats or decomposes.

troposphere. The lowest layer of the atmosphere and the zone in which most weather events occur. See also atmosphere, stratosphere.

U

utilitarian justification.  A rationale for the conservation of nature based on the idea that the environment provides individuals with direct economic benefits. Compare ecological justification, moral justification, aesthetic arguments.

V

vertebrates. Animals with backbones, including fish, amphibians, reptiles, birds, and mammals. Compare invertebrates.

W

water resources. The network of rivers, lakes, and other surface waters that supply water for food production and other essential human systems.

watershed. A region of high ground that lies between and determines the flow of two unconnected drainage systems, such as the Continental Divide, which is formed by the Rocky Mountains.

wetlands. Transitional areas between aquatic and terrestrial ecosystems, usually covered with fresh water for part of the year, with characteristic soils and vegetation.

withdrawal uses. Water that is removed from its natural setting for municipal use, irrigation, manufacturing, and other applications. See also instream uses.

worldview. A set of commonly held values, ideas, and images concerning the nature of reality and the role of humanity within it.

X 

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Z