A. What are the two major characteristics that change when air is heated and cooled? (2 points)
B. How do these characteristics change the movement of air? (6 points)
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C. What is the name of the cycle that develops during these changes? (2 points)
D. Draw a diagram to illustrate this process. (4 points)
E. Why do the changes you described in part B provide an example of a cycle? (4 points)

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.