Across
- 3. together with the non-living constituents of the environment form
- 5. the act or process of establishing a forest especially on land not previously forested.
- 7. The first trophic level.
Down
- 1. All the interacting organisms in an
- 2. chain This series or organisms taking part at
- 4. biotic levels form a food chain
- 6. _______.