| A | B |
|---|
| Nitrogen | 70% of the atmosphere |
| Nitrogen Fixation | A process that converts atmospheric nitrogen into nitrate |
| Root Nodules | Contain nitrogen-fixing bacteria. Found in leguminous plants. |
| Nitrification | The process of converting ammonium salts into nitrates |
| Lightning | Physical process that fixes atmospheric nitrogen into the soil |
| Amino acid | Nitrogen-containing sub-unit of protein |
| Eating | How nitrogen is obtained by animals |
| Bacteria | The living organisms which fix nitrogen to be used by other organisms |
