| A | B |
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| ecology | the study of the interactions between organisms and the other living and nonliving components of their environment |
| biosphere | the part of Earth where life exists; includes all of the living organisms on Earth |
| ecosystem | a community of organisms and their abiotic environment |
| community | a group of various species that live in the same habitat and interact with each other |
| population | a group of organisms of the same species that live in a specific geographical area that interbreed |
| biotic factor | an environmental factor that is associated with or results from the activities of living organisms |
| abiotic factor | an environmental factor that is not associated with the activities of living organisms |
| producer | an organism that can make organic molecules from inorganic molecules; a photosynthetic or chemosynthetic autotroph that serves as the basic food source for an ecosystem |
| consumer | an organisms that eats other organisms or organic matter instead of producing its own nutrients or obtaining nutrients from inorganic sources |
| trophic level | an organism's relative position in a sequence of energy transfers ina fodd chain or food pyramid, examples include producers and primary, secondary and tertiary consumers |
| food web | a diagram that shows the feeding relationships among organisms in an ecosystem |
| water cycle | the continuous movement of water between the atmosphere, the land and the oceans |
| carbon cycle | the movement of carbon from the nonliving environment into living things and back |
| nitrogen cycle | the process in which nitrogen circulates among the air, soil, water, plants and animals in an ecosystem |
| food chain | the pathway of energy transfer through various stages as a result of feeding patterns of a series of orgnanisms |
| limiting factor | an environmental factor that prevents an organism or population from reaching its full potential of distribution or activity |
| carrying capacity | the largest population that an environment can support at any given time |
| density-dependent factors | a variable affected by the number of organisms present in a given area |
| predation | a relationship between two species in which one species, the predator, feeds on the other species, the prey |
| competition | a type of interaction where two or more species use the same limited resource |
| symbiosis | a relationship in which two different organisms live in close association with each other |
| parasitism | a relationship between two species in which one species, the parasite, benefits from the other species, the host, which is harmed |
| mutualism | a relationship between two species in which both species benefit |
| commensalism | a relationship between two organisms in which one organism benefits and the other is unaffected |
| ecological succession | a gradual process of change and replacement in a community |
