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In Chapter 56 we looked at communities and the roles that species play in shaping their structure and function. In this chapter we will consider how energy flows and nutrients cycle through communities, a branch of ecology known as ecosystem science.
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Ecosystems include all the organisms in a given area and their physical and chemical environment.
Energy sources in ecosystems result from the processes of photosynthesis, chemosynthesis, and metabolism; energy is transferred via primary and secondary production.
Autotrophs and heterotrophs obtain required nutrients in different ways.
An ecosystem is all the organisms in a given area and the physical and chemical environment in which they live. The term was first coined by A. G. Tansley, a plant ecologist who was interested in how the flow of energy and chemicals was influenced by both the biotic and abiotic components of the environment.
Just like communities, ecosystems occupy a wide range of spatial scales, making them hard to delineate precisely (see Key Concept 56.1). For that reason, ecologists often define an ecosystem using subsets of species and components of the physical and chemical environment based on the questions they are investigating. For example, a soil ecosystem might include only the bacteria that transform nitrogen into forms plants can use. Or an estuarine ecosystem might be confined to the cycling of carbon through a food web of algae and their consumers, as you saw in the opening story.