According to the University of British Columbia, "An ecosystem is a community of plants, animals and smaller organisms that live, feed, reproduce and interact in the same area or environment." Ecosystems range in size from microscopic environments up to the entire intertwined environment of Earth (known as the "biosphere"). The number of ecosystems on Earth is countless and each ecosystem is distinct. Despite the myriad types of ecosystems and their diverse range, all ecosystems have several characteristics in common that help define them.
Ecosystems Are Hierarchical
All ecosystems have a feeding hierarchy. The hierarchy includes an energy source (e.g., the sun) and producers, consumers, decomposers and non-living chemicals such as minerals and other elements. These components depend on one another.
Ecosystems may contain grazer food webs in which plants (i.e., producers) absorb non-living nutrients with the help of the sun. Animals (i.e., consumers) eat plants and other animals to take in nutrients. When plants and animals die or when animals excrete waste, bacteria (i.e., decomposers) feed on the waste materials. The nutrients then go back into the water and/or soil for re-absorption by producers. A detritus food web occurs in the absence of sunlight. In a detritus food web, the energy comes from dead matter (i.e., detritus) instead of green producers. One example of a detritus food web is the ecosystem of a deciduous forest floor.
Ecosystems Have Biodiversity
Earth is thought to have over 10 million different species of life, and ecosystems depend on such biodiversity for survival. Because each organism in an ecosystem has a purpose (i.e., a niche), the loss of just one species from an ecosystem could significantly shift the balance. According to the Environmental Protection Agency, "recent studies suggest that reductions in biodiversity can alter both the [size] and the stability of ecosystems."
If biodiversity in an ecosystem declines, the system may become more susceptible to environmental occurrences such as drought and other problems such as disease and pests. For example, tropical rain forests are complex ecosystems full of biodiversity. Plants and animals in a rain forest thrive because of the natural balance of the ecosystem. When a rain forest ecosystem is altered to support a banana farm, pest problems abound.
Ecosystems Have Regular Temperature and Rainfall Patterns
Due to complicated global climate patterns, different areas have unique and relatively cyclical climates.
Ecosystems form in response to the unique but predictable climate of each geographic area. Unique ecosystems will form in different climates. Likewise, since elevation and topography affect climate, different ecosystems will form at different elevations. The life that exists in any given ecosystem is the direct result of elevation, topography and temperature and rainfall patterns. For example, the vegetation of a desert ecosystem is sparse due to temperature extremes and lack of rainfall. The plant life that does exist is adapted to conserve water. Desert fauna also have adapted for water conservation, and since desert plants are important sources of water for the animals, many desert plants have developed extreme protection methods (e.g., cactus needles).