| I: | conversion of inorganic into organic material, with the help of the radiant energy of the sun, by the autotrophs |
| II: | consumption of the autotrophs by heterotrophs; |
| III: | decomposition and mineralization of the dead matter to release them back for reuse by the autotrophs. |
| Statement I: | In a particular climatic condition, decomposition rate is quicker if detritus is rich in lignin and chitin, and slower, if detritus is rich in nitrogen and water-soluble substances like sugars. |
| Statement II: | Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition. |
| I: | The trophic level of an organism is the position it occupies in a food web. |
| II: | The trophic level represents species and not a functional level. |
| III: | A given organism occupies only one trophic level in a food chain. |
| IV: | The trophic level of an organism is the number of steps it is from the start of the chain. |
| Assertion (A): | Organisms at each trophic level depend on those at the lower trophic level for their energy demands. |
| Reason (R): | The amount of energy decreases at successive trophic levels. |
| 1. | Both (A) and (R) are true and (R) correctly explains the (A). |
| 2. | (A) is true but (R) is false |
| 3. | (A) is false but (R) is true |
| 4. | Both (A) and (R) are true but (R) does not correctly explain the (A). |