Answer
8. c. The nitrogen cycle
Work Step by Step
Nitrogen fixing bacteria-- found in the roots of some plants -- legumes--can fix nitrogen and transform it into nitrates. These compounds (NO3-) are used by plants in nucleic acid and protein syntheses. When plants die their tissues are converted by decomposers -- aerobic and anerobic bacteria-- into ammonium (NH4+) compounds. Nitrifying bacteria transform ammonium compounds to nitrites (NO2-) and then to nitrates (NO3-) which plants can use as nutrients.
