Ecosystems Assignment



Writing Assignment on Ecosystems

Complete the following questions and submit answers for grade. (10 pts each)

1. We hear the word ecosystem used frequently in the news today. In your own words, explain what an ecosystem is. Be specific.

2. Describe in as much detail as you can what factors determine the type of ecosystem (biome) found in a given geographic area.

3. Select an ecosystem (pond, salt marsh, deciduous forest, old field, etc.) and explain a food web that occurs in that ecosystem. You may use a diagram if you wish. Label plants and animals as specifically as possible and indicate the trophic level they occupy. Make sure you include decomposers.

4. It is intuitively obvious that there are few large predators in an ecosystem; there is even a book about why large, fierce animals are rare. The grizzly bear requires any where from 11 square miles to 1000 square miles of habitat for its home range. The average in the Brooks Range of Alaska where there is minimal human interference is 521 square miles. Range size seems to be at least a factor of richness of food supplies. From your knowledge of energy flow, trophic structure and ecological pyramids, explain why the grizzly bear needs such a large range to survive, or , as it is put in Asia, why there is only one tiger to a hill.

5. Using nitrogen as an example, explain how biogeochemical cycles work. How is nitrogen "lost" from ecosystems and how is it "replaced"?

6. When a farm is abandoned, as has frequently happened in most parts of the U.S., the land goes through a series of changes. Assuming  that this were to happen near where you live, describe in detail what would happen to the ecosystem--be specific. Explain how this process differs from primary succession?

7. A corn or cotton field has very little biotic diversity; that is intentional in this case. Farmers spend a great deal of time money, and energy maintaining this "simple" ecosystem. Compare this type of ecosystem with a mature forest ecosystem in terms of stability and identify the factors which account for this difference.

8. Using the concepts of habitat and niche, explain why complex ecosystems (such as a rainforest) have more diversity than simpler ones (such as a grassland).

9. Explain the difference between predation and symbiosis. If a predator species uses only a single prey species, explain how this differs from parasitism, or not.


When you have completed this assignment, go on to climate under the Biomes portion of this Unit.

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