abiotic
Nonliving.
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.
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.
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).
atmosphere
The whole mass of air surrounding the earth.
biomass
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; plan
biome
Terrestrial regions inhabited by certain types of life, especially vegetation. Examples are various types of deserts, grasslands, and forests.
biosphere
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 wate
biotic
living organisms
carbon cycle
Cyclic movement of carbon in different chemical forms from the environment to organisms and then back to the environment.
carnivore
Animal that feeds on other animals.
chemosynthesis
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.
community
populations of all species living and interacting in an area at a particular time
consumer
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 (
decomposer
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 retu
detritivore
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.
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.
distribution
Area over which we can find a species.
ecological efficiency
Percentage of energy transferred from one trophic level to another in a food chain or web.
ecosystem
Community of different species interacting with one another and with the chemical and physical factors making up its nonliving environment.
food chain
Series of organisms in which each eats or decomposes the preceding one.
food web
Complex network of many interconnected food chains and feeding relationships.
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.
fresh water 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 standing (lentic) bodies of fresh water such as lakes, ponds, and inland wetlands an
genetic diversity
Variability in the genetic makeup among individuals within a single species
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.
habitat
place or type of place where an oranism or population of organisms lives
herbivore
Plant-eating organism. Examples are deer, sheep, grasshoppers, and zooplankton.
humus
Slightly soluble residue of undigested or partially decomposed organic material in topsoil. This material helps retain water and water-soluble nutrients, which can be taken up by plant roots.
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.
hydrosphere
The earth's liquid water (oceans, lakes, other bodies of surface water, and underground water), frozen water (polar ice caps, floating ice caps, and ice in soil, known as permafrost), and water vapor in the atmosphere.
infiltration
downward movement of water through soil
leaching
Process in which various chemicals in upper layers of soil are dissolved and carried to lower layers and, in some cases, to groundwater.
limiting factor
Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem.
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.
lithosphere
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
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
net primary productivity
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 o
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.
nutrient
Any food or element an organism must take in to live, grow, or reproduce
omnivore
Animal that can use both plants and other animals as food sources. Examples are pigs, rats, cockroaches, and people. Compare carnivore, herbivore.
organism
Any form of life.
phosphorus cycle
Cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment.
photosynthesis
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
population
Group of individual organisms of the same species living in a particular area
primary consumer
Organism that feeds on all or part of plants (herbivore) or on other producers. Compare detritivore, omnivore, secondary consumer.
producer
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
pyramid of energy flow
Diagram representing the flow of energy through each trophic level in a food chain or food web. With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophi
range of tolerance
Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally.
salinity
Amount of various salts dissolved in a given volume of water
secondary cosumer
Organism that feeds only on primary consumers
soil
Complex mixture of inorganic minerals (clay, silt, pebbles, and sand), decaying organic matter, water, air, and living organisms.
soil horizons
Horizontal zones that make up a particular mature soil. Each horizon has a distinct texture and composition that vary with different types of soils
soil profile
Cross-sectional view of the horizons in a soil
soill texture
Relative amounts of the different types and sizes of mineral particles in a sample of soil
species
Group of organisms that resemble one another in appearance, behavior, chemical makeup and processes, and genetic structure. Organisms that reproduce sexually are classified as members of the same species only if they can actually or potentially interbreed
stratoshpere
Second layer of the atmosphere, extending about 17[[endash]]48 kilometers (11[[endash]]30 miles) above the earth's surface. It contains small amounts of gaseous ozone (O3), which filters out about 95% of the incoming harmful ultraviolet (UV) radiation emi
sulfur cycle
Cyclic movement of sulfur in different chemical forms from the environment to organisms and then back to the environment
tertiary (higher-level) consumers
Animals that feed on animal-eating animals. They feed at high trophic levels in food chains and webs. Examples are hawks, lions, bass, and sharks.
trophic level
All organisms that are the same number of energy transfers away from the original source of energy (for example, sunlight) that enters an ecosystem. For example, all producers belong to the first trophic level, and all herbivores belong to the second trop
trophosphere
Innermost layer of the atmosphere. It contains about 75% of the mass of earth's air and extends about 17 kilometers (11 miles) above sea level
weathering
Physical and chemical processes in which solid rock exposed at earth's surface is changed to separate solid particles and dissolved material, which can then be moved to another place as sediment.