Ecology looks at energy transformations and biogeochemical cycling within ecosystems. Ecology is often defined as the interactions of organisms with each other and with the environment in which they occur. The basic components are important to nearly all types of ecosystems. Energy is continually input into an ecosystem in the form of light energy, and some energy is lost with each transfer to a higher trophic level. Nutrients, on the other hand, are recycled within an ecosystem, and their supply normally limits biological activity.
Energy is moved through an ecosystem via a food web, which is made up of interlocking food chains.
The amount of primary production determines the amount of energy available to higher trophic levels. The study of how chemical elements cycle through an ecosystem is termed biogeochemistry. A biogeochemical cycle can be expressed as a set of stores and transfers. A biome is a major vegetation type extending over a large area. Biome distributions are determined largely by temperature and precipitation patterns on the Earth's surface.