Define Open Ecosystem

Ecosystems cycle materials such as carbon, nitrogen and water among different levels of the ecosystem. In an open ecosystem, some of these materials enter or leave the ecosystem. By contrast, closed ecosystems have a fixed amount of material.

Factors in Closed Ecosystems

Two important factors in a closed ecosystem are the rate at which a chemical is cycled and the pathways through which it is cycled.

Factors in Open Ecosystems

In addition to the rate and pathway variables, open ecosystems are influenced by the amount of the chemical flowing into and out of the ecosystem.

Feedback in Ecosystems

Feedback refers to how the outcome in an ecosystem influences the ecosystem dynamics.

Positive Feedback

Positive feedback occurs when the outcome of an ecosystem event or process further destabilizes the ecosystem. For example, pollution entering a lake kills a number of fish, which depletes oxygen as they decompose, resulting in more fish dying.

Negative Feedback

Negative feedback occurs when the outcome of an ecosystem event or process works to stabilize the ecosystem. For example, an increase in caribou leads to overgrazing, which results in starvation that reduces the number of caribou.

References

• Marietta College: Environmental Biology Ecosystems
• University of Michigan: The Concept of the Ecosystem
• U.S. Climate Change Science Program: Ecosystems