VI. Role-play

Choose one of the following situations to act out.

1. Two post-graduates are talking about nutrient cycling, particularly about the various inputs and outputs of producers, consumers, de­tritus feeders and decomposers.

1. A scientist is explaining to an audience (which can be the whole class) the first basic principle of ecosystem sustainability and its harmony with the Law of Conservation of Matter. The audience can then ask questions.

1. Two young scientists are changing their views and opinions about the carbon cycle.

4- As a reporter at a conference, you are speaking about the phospho­rus cycle and an important difference between it and the carbon

64 Unit Five Ecosystems: How They Work 65

cycle. The participants (which can be the whole class) will then ask questions.

5. You are reporter and are interviewing a famous scientist about the nitrogen cycle. You are especially interested in different nitrogen fixations (biological, atmospheric). You are asking him many ques­tions and he is answering them.

5. Two adult students are preparing for their examination on the ni­trogen cycle. They are discussing nitrogen-fixing organisms and how all natural ecosystems depend on them.

5. Two middle-income farmers are discussing the high cost of indus­trially fixed nitrogen.

5. Two farmers are discussing problems of enriching the soil by nitro­gen. They are discussing two ways of doing this: applying fertilizers and alternating legumes with nonlegume crops.

5. A teacher is explaining to a group of adult students (which can be the whole class) the phosphorus cycle, and an important differ­ence between the carbon cycle and the phosphorus cycle. The stu­dents can then ask questions.

5. Two environmentalists are changing their views and opinions about very serious case of humans interfering with the phosphorus cycle that is seen in the cutting of tropical rainforests.

VII. FOR DISCUSSION AND COMPOSITION Choose one of the following to discuss or write about.

1. What do we know about nutrient cycling today?

1. Explain the first basic principle of ecosystem sustainability.

1. Describe the carbon cycle starting with the "reservoir" of carbon dioxide molecules present in the air and dissolved in water.

1. Describe the phosphorus cycle. What is usually referred to as or­ganic phosphate?

1. Compare the carbon cycle and the phosphorus cycle. What is an important difference between them?

1. Discuss a very serious case of humans interfering with the phos­phorus cycle that is seen in the cutting of tropical rainforests.

1. Describe the nitrogen cycle. Why is it more complex than the car­bon cycle and the phosphorus cycle?

g. Compare biological nitrogen fixation and atmospheric nitrogen fix­ation.

9. Compare the nitrogen cycle in terrestrial and aquatic ecosystems. What are the most significant nitrogen fixers in both ecosystems?

9. Describe industrial nitrogen fixing. Why do many farmers readopt the natural process of enriching the soil by crop rotation?

9. Where does phosphate from agricultural croplands make its way? Why does this addition result in overfertilization?

9. What are major constituents of fertilizer? Why do many farmers have to readopt the natural process of enriching the soil by crop rotation?