Term | Definition |
Food chain | A series of steps in which organisms transfer energy by eating or being eaten. |
Food web | A network of food chains. |
Trophic level | An individual step within a food chain, food web, or pyramid. |
Ecological pyramid | Shows the relative amount of energy available at each trophic level of a food chain or food web. |
Energy pyramid | A diagram that shows the loss of energy in an ecosystem; the greatest amount of energy is found at the bottom. |
Biomass pyramid | A diagram that shows how an ecosystem's weight by species is distributed; largest group is producers (found at bottom). |
Pyramid of numbers | A diagram that shows the relative numbers of different species in an ecosystem; largest amounts are at the bottom. |
Biomass | The total amount of living material in a given habitat, population, or sample; number is expressed as a mass that can be measured on a balance. |
Biogeochemical cycle | Matter is recycled within and between ecosystems in closed loops. |
Water cycle | Water continuously moving between oceans, the atmosphere, and the land. |
Nutrient cycle | Nutrients moved into and out of organisms to build tissue and carry out life functions. |
Carbon cycle | Carbon is continuously exchanged between the atmosphere and oceans. |
Nitrogen cycle | Nitrogen exists in many forms (as ammonia and nitrogen compounds) and is continuously recycled. |
Phosphorous cycle | Found as inorganic compounds in rocks and minerals; cycles through using plants. |
Denitrification | Bacteria convert nitrates into nitrogen gas to get energy. |
Competition | Occurs when two organisms attempt to use the same resource (food, space, a mate) at the same time. |
Competitive exclusion principle | No two species can occupy the same niche at the same time. |
Keystone species | A single species in an ecosystem that, if changed, can impact the entire ecosystem. |
Biodiversity | Sum total of all of the different species of habitats and organisms that make up the Earth. |
Ecological succesion | Series of changes that occur in a community over time. |
Primary succesion | Begins in an area with no remnants of an older community; usually occurs after a natural disaster (volcano or earthquake). |
Secondary succesion | Occurs in ecosystems where an existing community was not fully disturbed/destroyed; usually occurs after wildfires or hurricanes or human activities. |
Pioneer species | First species to colonize barren areas after natural disaster; usually lichens and mosses. |
Climax community | The original community that existed before a natural disaster. |
Carrying capacity | Maximum number of individuals that the environment can support. |
Native species | An organism that "belongs" in the ecosystem; has evolved with the ecosystem (Canada goose). |
Invasive species | An organism that successfully takes over an organism's niche and is not native to the area (Burmese python, Asian long horned beetle). |
Deforestation | Destruction of forests for the increased clearing of land to create farms and homes for the increasing world population; can lead to other environmental issues. |