Across
- 2. layers of gases surrounding earth
- 5. to protect from harm or destruction
- 8. convert into usable material
- 12. trash of the sidewalk
- 13. decayed organic material
- 15. food produced without the use of chemical fertilizers or pesticides
- 17. surroundings a person, plant or animal lives or operates
- 18. capable of being renewed
- 19. garbage dump
- 20. to contaminate with harmful poisonous substance
Down
- 1. reuse
- 3. no longer in existence
- 4. community of interacting organisms and their physical environment
- 6. relating to the sun
- 7. branch of biology
- 9. production and discharge of something
- 10. able to be maintained at a certain level
- 11. to maintain to its original state
- 14. a colorless gas which is a poisonous form of oxygen
- 16. where an animal lives