| A | B |
|---|
| Bacterial nitrogen fixation | Bacteria convert N2 in the atmosphere to usable nitrogen ions. |
| Atmospheric nitrogen fixation | Lightning converts N2 in the atmosphere to usable nitrogen ions. |
| Root uptake | How plants get nitrogen. |
| Decomposition | How nitrogen from dead organisms is released back to the environment. |
| Feeding | How humans and other animals get their nitrogen. |
| Denitrification | Bacteria convert nitrates and nitrites to atmospheric nitrogen, N2 |
| Fertilizer | Nitrogen-rich compounds that can be man-made that are fed to plants. |
| DNA, RNA, and proteins | Molecules we use nitrogen in. |
| Excretion | How nitrogen leaves our bodies while we're still alive. |
