Defining an ecosystem

[Bernard NebelKeymaster]

An ecosystem is an assemblage of plants, animals, and microbes interacting with each other and the abiotic environment in such a way as to sustain the assemblage over indefinite time. (Note that ecosystems do not have distinct boundaries. One may grade into another and some species, e.g., migratory birds may occupy different ecosystems at different times of year.)

Three key features of every ecosystem that are basic its sustainability are:

1. Nutrients are recycled
2. It runs on solar energy which is constant and everlasting (within any human timeframe)
3. Populations of all organisms involved are maintained in balance

Have students consider the dominant natural ecosystem of their region, with which they should have gained considerable familiarity by now, and relate these features (above) to that ecosystem. Reinforce discussion with diagrams that show:

Regarding recycling of nutrients

The carbon cycle. Type into your browser: carbon cycle images

The nitrogen cycle. Type into your browser: nitrogen cycle images

The phosphorus cycle. Type into your browser: phosphorus cycle images

Regarding running on solar energy,

Type into your browser: energy flow in ecosystems images

Please post questions and/or comments and suggest readings and additional videos.

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