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Author(s): Deanne Erdmann MS


An ecosystem is composed of all interacting organisms (biota) along with their physical and chemical environments. Physical aspects of an ecosystem, called abiotic components, include variables related to temperature, sunlight, soil, and other factors.

Ecosystems vary in size from microscopic environments to large geographical areas. The boundaries of an ecosystem are not usually distinct and the activities of one ecosystem often impact other ecosystems. Some ecologists consider the biosphere as a global ecosystem.

Ecosystem diversity can be measured by the richness of genetic diversity within individual species, by the number of different species present, and the variety of habitats. Diverse ecosystems are believed to be more stable and productive.

Energy and nutrients (chemicals) continuously move through ecosystems. Because energy cannot be recycled, a continuous input is required, almost always by sunlight. Elements such as carbon, sulfur, phosphorus, and nitrogen are recycled within ecosystems through biogeochemical cycles. Both energy and chemicals are transferred by photosynthesis and feeding relationships. The flow of carbon through ecosystems closely parallels the flow of energy.

Over long periods of time, ecosystems change in appearance and composition. Succession is the regular replacement of populations in a habitat. Some communities may follow a recognizable sequence of change ending in a relatively stable community referred to as a climax community. Recently, the concept of climax community has generated considerable debate as the endpoints of a succession depend on the introduction of complex environmental factors.