An ecosystem consists of a community of living organisms
interacting with each other and the environment. The source of energy that fuels most ecosystems is the sun. Plants use the Sun’s energy to produce food in a process called photosynthesis.
Organisms that use energy from the Sun or energy stored in chemical compounds to produce their own nutrients are called autotrophs. They are also called producers because most other organisms depend on autotrophs for food and energy. Heterotrophic organisms that can’t make their own food may obtain nutrients by eating other organisms. A heterotroph that feeds only on plants is called an herbivore. Herbivores are also called first order heterotrophs. Heterotrophs that feed on other herbivores are second order heterotrophs.
