Chapter 4


Nonliving. Compare biotic.


Adjustment to slowly changing new conditions. Compare threshold effect.

aerobic respiration

Complex process that occurs in the cells of most living organisms, in which nutrient organic molecules such as glucose (C6H12O6) combine with oxygen (O2) and produce carbon dioxide (CO2), water (H2O), and energy. Compare photosynthesis.

anaerobic respiration

Form of cellular respiration in which some decomposers get the energy they need through the breakdown of glucose (or other nutrients) in the absence of oxygen. Compare aerobic respiration.


See producer.

basic solution

Water solution with more hydroxide ions (OH-) than hydrogen ions (H+); water solution with a pH greater than 7. Compare acid solution, neutral solution.

biogeochemical cycle

Natural processes that recycle nutrients in various chemical forms from the nonliving environment to living organisms and then back to the nonliving environment. Examples are the carbon, oxygen, nitrogen, phosphorus, sulfur, and hydrologic cycles.

biological community

See community.

biological diversity

See biodiversity.


Zone of earth where life is found. It consists of parts of the atmosphere (the troposphere), hydrosphere (mostly surface water and groundwater), and lithosphere (mostly soil and surface rocks and sediments on the bottoms of oceans and other bodies of water) where life is found. Sometimes called the ecosphere.


Living organisms. Compare abiotic.

carbon cycle

Cyclic movement of carbon in different chemical forms from the environment to organisms and then back to the environment.


Smallest living unit of an organism. Each cell is encased in an outer membrane or wall and contains genetic material (DNA) and other parts to perform its life function. Organisms such as bacteria consist of only one cell, but most of the organisms we are familiar with contain many cells. See eukaryotic cell, prokaryotic cell.


Process in which certain organisms (mostly specialized bacteria) extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight. Compare photosynthesis.


Populations of all species living and interacting in an area at a particular time.


Organism that cannot synthesize the organic nutrients it needs and gets its organic nutrients by feeding on the tissues of producers or of other consumers; generally divided into primary consumers (herbivores), secondary consumers (carnivores), tertiary (higher-level) consumers, omnivores, and detritivores (decomposers and detritus feeders). In economics, one who uses economic goods.


Consumer organism that feeds on detritus, parts of dead organisms, and cast-off fragments and wastes of living organisms. The two principal types are detritus feeders and decomposers.


Parts of dead organisms and cast-off fragments and wastes of living organisms.

detritus feeder

Organism that extracts nutrients from fragments of dead organisms and their cast-off parts and organic wastes. Examples are earthworms, termites, and crabs. Compare decomposer.

dissolved oxygen (DO) content

Amount of oxygen gas (O2) dissolved in a given volume of water at a particular temperature and pressure, often expressed as a concentration in parts of oxygen per million parts of water.

ecological diversity

The variety of forests, deserts, grasslands, oceans, streams, lakes, and other biological communities interacting with one another and with their nonliving environment. See biodiversity. Compare functional diversity, genetic diversity, species diversity.

ecological efficiency

Percentage of energy transferred from one trophic level to another in a food chain or web.


Community of different species interacting with one another and with the chemical and physical factors making up its nonliving environment.

ecosystem services

Natural services or natural capital that support life on the earth and are essential to the quality of human life and the functioning of the world's economies. See natural resources.

eukaryotic cell

Cell containing a nucleus, a region of genetic material surrounded by a membrane. Membranes also enclose several of the other internal parts found in a eukaryotic cell. Compare prokaryotic cell.


Conversion of a liquid into a gas.


See anaerobic respiration.

food chain

Series of organisms in which each eats or decomposes the preceding one. Compare food web.

food web

Complex network of many interconnected food chains and feeding relationships. Compare food chain.

functional diversity

Biological and chemical processes or functions such as energy flow and matter cycling needed for the survival of species and biological communities. See biodiversity, ecological diversity, genetic diversity, species diversity.

genetic diversity

Variability in the genetic makeup among individuals within a single species. See biodiversity. Compare ecological diversity, functional diversity, species diversity.

gross primary productivity (GPP)

The rate at which an ecosystem's producers capture and store a given amount of chemical energy as biomass in a given length of time. Compare net primary productivity.


See consumer.

hydrologic cycle

Biogeochemical cycle that collects, purifies, and distributes the earth's fixed supply of water from the environment to living organisms and then back to the environment.


The earth's (1) liquid water (oceans, lakes, other bodies of surface water, and underground water), (2) frozen water (polar ice caps, floating ice caps, and ice in soil, known as permafrost), and (3) small amounts of water vapor in the atmosphere. See also hydrologic cycle.

law of tolerance

The existence, abundance, 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 threshold effect.

limiting factor

Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem. See limiting factor principle.

limiting factor principle

Too much or too little of any abiotic factor can limit or prevent growth of a population of a species in an ecosystem, even if all other factors are at or near the optimum range of tolerance for the species.


Organisms such as bacteria that are so small that they can be seen only by using a microscope.

natural greenhouse effect

Heat buildup in the troposphere because of the presence of certain gases, called greenhouse gases. Without this effect, the earth would be nearly as cold as Mars, and life as we know it could not exist. Compare global warming.

nitrogen cycle

Cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment.

nitrogen fixation

Conversion of atmospheric nitrogen gas into forms useful to plants by lightning, bacteria, and cyanobacteria; it is part of the nitrogen cycle.


Any food or element an organism must take in to live, grow, or reproduce.

nutrient cycle

See biogeochemical cycle.


Animal that can use both plants and other animals as food sources. Examples are pigs, rats, cockroaches, and people. Compare carnivore, herbivore.


Any form of life.


Passage of a liquid through the spaces of a porous material such as soil.

phosphorus cycle

Cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment.


Complex process that takes place in cells of green plants. Radiant energy from the sun is used to combine carbon dioxide (CO2) and water (H2O) to produce oxygen (O2) and carbohydrates (such as glucose, C6H12O6) and other nutrient molecules. Compare aerobic respiration, chemosynthesis.


Water in the form of rain, sleet, hail, and snow that falls from the atmosphere onto the land and bodies of water.

primary consumer

Organism that feeds on all or part of plants (herbivore) or on other producers. Compare detritivore, omnivore, secondary consumer.


A mathematical statement about how likely it is that something will happen.


Organism that uses solar energy (green plant) or chemical energy (some bacteria) to manufacture the organic compounds it needs as nutrients from simple inorganic compounds obtained from its environment. Compare consumer, decomposer.

pure free-market economic system

System in which all economic decisions are made in the market, where buyers and sellers of economic goods interact freely, with no government or other interference. Compare capitalist market economic system, pure command economic system.


Isotope of an atom that spontaneously emits one or more types of radioactivity (alpha particles, beta particles, gamma rays).


Ability of a living system to restore itself to original condition after being exposed to an outside disturbance that is not too drastic. See constancy, inertia.


Amount of various salts dissolved in a given volume of water.

solid waste

Any unwanted or discarded material that is not a liquid or a gas. See municipal solid waste.

subsistence farming

Supplementing solar energy with energy from human labor and draft animals to produce enough food to feed oneself and family members; in good years there may be enough food left over to sell or put aside for hard times. Compare industrialized agriculture.

surface mining

Removing soil, subsoil, and other strata and then extracting a mineral deposit found fairly close to the earth's surface. See area strip mining, contour strip mining. See area strip mining, contour strip mining, dredging, mountaintop removal, open-pit mining. Compare subsurface mining.

theory of island biogeography

The number of species found on an island is determined by a balance between two factors: the immigration rate (of species new to the island) from other inhabited areas and extinction rate (of species established on the island). The model predicts that at some point the rates of immigration and extinction will reach an equilibrium point that determines the island's average number of different species (species diversity).

threshold effect

The harmful or fatal effect of a small change in environmental conditions that exceeds the limit of tolerance of an organism or population of a species. See law of tolerance.

traditional subsistence agriculture

Production of enough crops or livestock for a farm family's survival and, in good years, a surplus to sell or put aside for hard times. Compare industrialized agriculture, traditional intensive agriculture.

transmissible disease

A disease that is caused by living organisms (such as bacteria, viruses, and parasitic worms) and can spread from one person to another by air, water, food, or body fluids (or in some cases by insects or other organisms). Compare nontransmissible disease.

urban sprawl

Growth of low-density development on the edges of cities and towns. See smart growth.


Ability of a system to survive for some specified (finite) time.


Study of the interactions of living organisms with one another and with their nonliving environment of matter and energy; study of the structure and functions of nature.

matter-recycling economy

Economy that emphasizes recycling the maximum amount of all resources that can be recycled. The goal is to allow economic growth to continue without depleting matter resources and without producing excessive pollution and environmental degradation. Compare high-throughput economy, low-throughput economy.


Procedure a scientist uses to study some phenomenon under known conditions. Scientists conduct some experiments in the laboratory and others in nature. The resulting scientific data or facts must be verified or confirmed by repeated observations and measurements, ideally by several different investigators.


Capable of being broken down by decomposers.


Measure of the average speed of motion of the atoms, ions, or molecules in a substance or combination of substances at a given moment. Compare heat.

acid deposition

The falling of acids and acid-forming compounds from the atmosphere to the earth's surface. Acid deposition is commonly known as acid rain, a term that refers only to wet deposition of droplets of acids and acid-forming compounds.

acid rain

See acid deposition.


The whole mass of air surrounding the earth. See stratosphere, troposphere.


Unwanted rock and other waste materials produced when a material is removed from the earth's surface or subsurface by mining, dredging, quarrying, and excavation.

global warming

Warming of the earth's atmosphere because of increases in the concentrations of one or more greenhouse gases primarily as a result of human activities. See greenhouse effect, greenhouse gases.

fossil fuel

Products of partial or complete decomposition of plants and animals that occur as crude oil, coal, natural gas, or heavy oils as a result of exposure to heat and pressure in he earth's crust over millions of years. See coal, crude oil, natural gas.


Porous, water-saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water.

sulfur cycle

Cyclic movement of sulfur in different chemical forms from the environment to organisms and then back to the environment.

net primary productivity (NPP)

Rate at which all the plants in an ecosystem produce net useful chemical energy; equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy (gross primary productivity) and the rate at which they use some of that energy through cellular respiration. Compare gross primary productivity.


Organic matter produced by plants and other photosynthetic producers; total dry weight of all living organisms that can be supported at each trophic level in a food chain or web; dry weight of all organic matter in plants and animals in an ecosystem; plant materials and animal wastes used as fuel.


Variety of different species (species diversity), genetic variability among individuals within each species (genetic diversity), variety of ecosystems (ecological diversity), and functions such as energy flow and matter cycling needed for the survival of species and biological communities (functional diversity).


Place or type of place where an organism or population of organisms lives. Compare ecological niche.


Group of individual organisms of the same species living in a particular area.

aquatic life zone

Marine and freshwater portions of the biosphere. Examples include freshwater life zones (such as lakes and streams) and ocean or marine life zones (such as estuaries, coastlines, coral reefs, and the deep ocean).


Terrestrial regions inhabited by certain types of life, especially vegetation. Examples are various types of deserts, grasslands, and forests.


Physical properties of the troposphere of an area based on analysis of its weather records over a long period (at least 30 years). The two main factors determining an area's climate are temperature, with its seasonal variations, and the amount and distribution of precipitation. Compare weather.


Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients. Producers return most of these chemicals to the soil and water for reuse. Decomposers consist of various bacteria and fungi. Compare consumer, detritivore, producer.

freshwater life zones

Aquatic systems where water with a dissolved salt concentration of less than 1% by volume accumulates on or flows through the surfaces of terrestrial biomes. Examples are (1) standing (lentic) bodies of fresh water such as lakes, ponds, and inland wetlands and (2) flowing (lotic) systems such as streams and rivers. Compare biome.


Small, drifting plants, mostly algae and bacteria, found in aquatic ecosystems. Compare plankton, zooplankton.

rock cycle

Largest and slowest of the earth's cycles, consisting of geologic, physical, and chemical processes that form and modify rocks and soil in the earth's crust over millions of years.


See r-selected species.


Animal plankton. Small floating herbivores that feed on plant plankton (phytoplankton). Compare phytoplankton.


Process in which water is absorbed by the root systems of plants, moves up through the plants, passes through pores (stomata) in their leaves or other parts, and evaporates into the atmosphere as water vapor.


Animal that feeds on other animals. Compare herbivore, omnivore.


Plant-eating organism. Examples are deer, sheep, grasshoppers, and zooplankton. Compare carnivore, omnivore.

spaceship-earth worldview

View of the earth as a spaceship: a machine that we can understand, control, and change at will by using advanced technology. See planetary management worldview. Compare environmental wisdom worldview.

asexual reproduction

Reproduction in which a mother cell divides to produce two identical daughter cells that are clones of the mother cell. This type of reproduction is common in single-celled organisms. Compare sexual reproduction.

sedimentary rock

Rock that forms from the accumulated products of erosion and in some cases from the compacted shells, skeletons, and other remains of dead organisms. Compare igneous rock, metamorphic rock. See rock cycle.


Downward movement of water through soil.


Outer shell of the earth, composed of the crust and the rigid, outermost part of the mantle outside the asthenosphere; material found in earth's plates. See crust, mantle.


An ionized gas consisting of electrically conductive ions and electrons. It is known as a fourth state of matter.