| A | B |
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| ecology | scientific study of interactions among organisms and between organisms and their environment |
| biosphere | part of Earth in which life exists including land, water, and air or atmosphere |
| species | group of similar organisms that can breed and produce fertile offspring |
| population | group of individuals of the same species that live in the same area |
| community | assemblage of different populations that live together in a defined area |
| ecosystem | collection of all the organisms that live in a particular place, together with their nonliving environment |
| biome | group of ecosystems that have the same climate and dominant communities |
| autotroph | organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer |
| producer | organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called an autotroph |
| photosynthesis | process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches |
| chemosynthesis | process by which some organisms, such as certain bacteria, use chemical energy to produce carbohydrates |
| heterotroph | organism that obtains energy from the foods it consumes; also called a consumer |
| consumer | organism that relies on other orgaisms for its energy and food supply; also called a heterotroph |
| herbivore | organism that obtains energy by eating only plants |
| carnivore | organism that obtains energy by eating animals |
| omnivore | organism that obtains energy by eating both plants and animals |
| dentrivore | organisms that feed on plant and animal remains and other dead matter, collectively called dentritus |
| decomposer | organism that breaks down and obtains energy from dead organic 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 |
| ecological pyramid | diagram that shows the relative amounts of energy or matter within each trophic level in a food chain or web |
| biomass | total amount of living tissue within a given trophic level |
| biogeochemical cycle | process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another |
| evaporation | process by which water changes from a liquid into an atmospheric gas |
| transpiration | loss of water from a plant through its leaves |
| nutrient | chemical substance that an organism needs to live |
| nitrogen fixation | process of converting nitrogen gas into ammonia |
| denitrification | conversion of nitrate into nitrogen gas |
| primary productivity | rate at which organic matter is created by producers in an ecosystem |
| 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 |
