| 1. | They thrive in environments with high concentrations of nitrogen and sulphur compounds. |
| 2. | They are sensitive to airborne pollutants, which disrupt their symbiotic relationship. |
| 3. | They absorb heavy metals from the environment promoting their growth. |
| 4. | They can metabolize and break down organic pollutants in the air. |
| I: | Fungi: Saprotrophs |
| II: | Lichens: Mutualism |
| III: | Malarial parasite in human RBC-commensal |