| A | B |
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| biogeography | the study of where plants and animals live throughout the world |
| biological clock | an internal timer that keeps track of a cycle of time and helps an organism stay in step with rhythmic cycles of change in the environment |
| biome | a division based on climate, plants, and animals; an environment that has a characteristic type of climax community |
| canopy | the layer of a forest biome that consists of the tops of trees; the "roof" of a forest |
| captive breeding | the practice of getting animals in zoos to have offspring |
| carbon cycle | the cyclical series of processes in which carbon moves through the living and nonliving parts of the environment |
| climax community | the stable community that is the final stage of succession |
| commensalism | a form of symbiosis in which one organism benefits and the other is not harmed |
| community | the living part of an ecosystem competition: the type of interaction in which organisms struggle with one another to obtain resources |
| conifer | a plant, usually an evergreen tree, that produces its seeds in cones |
| consumer | an organism that cannot make its own food |
| decomposer | an organism that breaks down the bodies of dead organisms into simpler substances |
| deforestation | : the destruction of forests |
| desertification | the process in which desertlike conditions are created |
| dispersal | the movement of living things from one place to others; spreading out |
| diurnal | active during the day ecological succession |
| ecology | the study of the relationships and interactions of living things with one another and with their environment |
| ecosystem | a unit consisting of all the living and nonliving things in a given area that interact with one another |
| endangered | in danger of becoming extinct |
| estivation | a summer resting state |
| estuary | an environment found at the boundary between fresh water and saltwater that contains a mixture of fresh water and saltwater |
| exotic species | a species that is not native to a place extinct: no longer in existence; used to describe subspecies, species, and so on, in which there are no living individuals |
| food chain | a representation of a series of events in which food energy and matter are transferred from one organism to another |
| food web | a diagram that consists of many overlapping food chains |
| freshwater biome | the biome that consists of the Earth's bodies of fresh water, such as lakes, ponds, streams, and rivers |
| habitat | the place in which an organism lives and obtains the resources it needs to survive |
| hibernation | a winter resting state |
| host | an organism that provides a home for another organism; in parasitism, the organism that is harmed by the parasite |
| marine biome | the ocean biome |
| migration | the movement of organisms from one place to another in response to periodic environmental changes; usually refers to cyclical movements |
| mutualism | a form of symbiosis in which both organisms benefit |
| niche | an organism's role in an ecosystem, which includes everything the organism does and everything the organism needs in its environment |
| nitrogen cycle | the cyclical series of processes in which nitrogen moves from the nonliving parts of the environment to living thing and back again |
| nocturnal | active during the night |
| parasite | an organism that lives on or inside the body of a host organism and harms the host |
| parasitism | a form of symbiosis in which one organism benefits and the other is harmed |
| permafrost | the layer of permanently frozen soil in the tundra |
| phytoplankton | microscopic producers (organisms that can make their own food) that live near the surface of the ocean and other bodies of water |
| population | a group of organisms of the same species living together in the same area |
| predator | an organism that kills and eats another organism |
| prey | an organism that is eaten by a predator |
| producer | an organism that is able to make its own food by using a source of energy to turn simple raw materials into food |
| symbiosis | a close relationship between two organisms in which one organism lives near, on, or even inside another organism and in which at least one - organism benefits |
| water cycle | the cyclical series of processes in which water moves through the living and nonliving parts of the environment |
| wildlife conservation | the intelligent management of living resources so that they provide the greatest possible benefit for the longest possible time |
| taiga | : the northernmost coniferous forest biome |
| oxygen cycle | the cyclical series of processes in which oxygen moves through the living and nonliving parts of the environment |
