Earth Day

2. Reuse in such a way as to create a product of higher quality or value than the original
9. A colorless unstable toxic gas with a pungent odor and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light. It differs from normal oxygen (O2) in having three atoms in its molecule (O3).
13. The surroundings or conditions in which a person, animal, or plant lives or operates
14. The production and discharge of something, especially gas or radiation
15. A biological community of interacting organisms and their physical environment.
17. The natural home or environment of an animal, plant, or other organism
18. Convert waste into reusable material
19. Contaminate with harmful or poisonous substances

1. The layers of gases surrounding a planet
3. Trash that is left lying in a public place
4. Able to be upheld or defended
5. The decayed organic material that is used as a plant fertilizer.
6. The branch of biology that deals with the relations of organisms to one another and to their physical surroundings
7. A source of energy that is not substantially depleted by use
8. Protect from harm or destruction
10. Maintain in its original or existing state
11. Type of energy from the sun
12. No longer in existence
16. Relating to or derived from living matter
20. A place to dispose of waste material by burying it and covering it with soil.