Across
- 3. Phosphorus makes up this important chemicals
- 4. What does to much phosphorus lead to in plants
- 6. How humans release CO2 into the atmosphere
- 8. How water returns to the ground in the water cycle
- 11. What is created by the decay of animal waste
- 12. activity Examples are mining and burning fossil fuels
- 15. What makes up 78% of the atmosphere
- 17. The process plants use to make sugar
- 18. Examples are volcanic eruptions and rock formation
- 19. The main regulator of CO2
Down
- 1. The main source of natural CO2
- 2. Main source of phosphorus from man
- 5. The process how animals use oxygen
- 7. Mostly contained in rocks and minerals
- 9. Activities performed by living organisms
- 10. Returns nitrogen to the soil
- 13. Eat plants that contain nitrogen
- 14. What do organisms use nitrogen for
- 15. Product rich in nitrogen
- 16. Chemical substances organisms need to sustain life