| A | B |
|---|
| Nitrogen Fixation is | the conversion of nitrogen gas into ammonia. |
| NItrification is | the conversion of ammonia or ammonium to nitrate. |
| Nitrate is | one of the main forms of nitrogen used by plants. |
| Assimilation is | the biological conversion of nitrates, ammonia, or ammonium into proteins and other nitrogen-containing compounds by plants. |
| Another part of assimilation is | the conversion of plant proteins into animal proteins. |
| Ammonification is | the conversion of organic nitrogen to ammonia and ammonium ions. |
| Denitrification is | the conversion of nitrate into nitrogen gas. |
| Humans have | more than doubled the amount of fixed nitrogen entering the global nitrogen cycle. |
| The excess nitrogen is | contributing to water-quality problems, air pollution, acid deposition, global warming, and depletion od atmospheric ozone. |
| The step after nitrogen fixation is | nitrification. |
| The step after nitrification could be | assimilation. |
| The step after nitrification could also be | denitrification. |
| The step after assimilation is | ammonification. |
| The step after ammonification is | denirtifiction. |
| The step after denitrification is | nitrogen fixation. |
