The Nitrogen Cycle

Instructions: Go to http://www.vtaide.com/png/nitrogenCycle.htm - Complete the diagram below by filling in the blanks. - Move your cursor over each component of the nitrogen cycle to learn more about it and then answer the questions below.

Questions on the Nitrogen Cycle

1. Why is nitrogen so important to all life? (refer also p. 25-27 in text) 2. Almost 79% of the atmosphere is nitrogen [N2(g)], but neither plants or animals can use this form of nitrogen directly. For use by organisms it must be supplied in the form of - the nitrate ion NO3 . Therefore, it must be “fixed” first. This is done through the - process of Nitrogen fixation (N2  NO3 ). List the three different ways atmospheric nitrogen is fixed.

3. Nitrogen fixation in soil: What type of relationship exists between Nitrogen-fixing bacteria and the plant it lives on?

Nodules

Explain how this relationship works.

What are nodules?

4. a) List the 3 decomposers involved in the nitrogen cycle.

b) What is the difference between aerobic and anaerobic bacteria?

c) What is the role of decomposers?

d) What is this process called? + - 5. a) What type of bacteria converts ammonium (NH4 ) to nitrates (NO3 )?

b) Why are nitrates so important?

6. What does denitrifying bacteria do?

7. What is assimilation?

8. a) How do animals get nitrogen?

b) How do you think animals return nitrogen to the soil?

9. How do plants return nitrogen to the soil?

10. Why do farmers use fertilizers?