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scientific study of interactions among organisms and between organisms and their environment


part of the earth in which life exists including land, water, and air or atmosphere


group of similar organisms that can breed and produce fertile offspring


group of individuals of the same species that live in the same area


assemblage of different populations that live together in a defined area


collection of all the organisms that live in a particular place, together with their nonliving environment


group of ecosystems that have the same climate and similar dominant communities


process my which some organisms use chemical energy to produce carbohydrates


organism that relies on other organisms for its energy and food supply; also called a heterotroph


organism that obtains energy by eating only plants


organism that obtains energy by eating animals


organism that obtains energy by eating both plants and animals


organism that feeds on plant and animal remains and other dead matter

food chain

series of steps in an ecosystem in which organisms transfer energy by eating and being eaten

food web

network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem

trophic level

step in a food chain or food web

energy pyramid

diagram that shows the relative amounts of energy or matter within each trophic level in a food chain or food web

biomass pyramid

a graphical representation designed to show the biomass or biomass productivity at each trophic level in a given ecosystem

water cycle

cycle of processes by which water circulates between the earth's oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration

carbon cycle

series of processes by which carbon compounds are interconverted in the environment, chiefly involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels

nitrogen cycle

series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation and decomposition


process by which water changes from a liquid into an atmospheric gas


loss of water from a plant through its leaves

nitrogen fixation

process of converting nitrogen gas into ammonia

limiting nutrient

single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem

algal bloom

an immediate increase in the amount of algae and other producers that results from a large input of a limiting nutrient

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