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Lesson Overview: Energy Flow in Ecosystems* Energy flows from one organism to the next in a food chain or food web.* Each step in a food chain or food web is called a trophic level.* The amount of energy available at each trophic level decreases as it moves up the pyramid.* There are three types of ecological pyramids: pyramids of energy, biomass, and numbers.Review: Pyramid of Energy* A pyramid of energy shows the relative amount of energy available at each trophic level.* Only about 10% of the original energy from producers is available to consumers.Pyramids of Biomass and Numbers* A pyramid of biomass illustrates the relative amount of living organic matter at each trophic level.* The greatest biomass is typically at the base of the pyramid, as seen in a field ecosystem.* A pyramid of numbers shows the relative number of individual organisms at each trophic level.* In most ecosystems, the shape of the pyramid of numbers is similar to the shape of the pyramid of biomass for the same ecosystem, with the numbers of individuals on each level decreasing from the level below it.Review: Pyramid of Biomass and Numbers* In some cases, however, consumers are much smaller than organisms they feed upon.* Thousands of insects may graze on a single tree, for example. The tree has a lot of biomass, but represents only one organism.* In such cases, the pyramid of numbers may be turned upside down.