Earth Day

2. 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)
5. contaminate (water, air, or a place) with harmful or poisonous substances.
7. the branch of biology that deals with the relations of organisms to one another and to their physical surroundings.
8. decayed organic material used as a plant fertilizer.
9. maintain (something) in its original or existing state.
11. protect (something, especially an environmentally or culturally important place or thing) from harm or destruction.
13. a biological community of interacting organisms and their physical environment
14. the envelope of gases surrounding the earth or another planet.
17. able to be maintained at a certain rate or level.
19. the production and discharge of something, especially gas or radiation.
20. trash, such as paper, cans, and bottles, that is left lying in an open or public place.

1. convert (waste) into reusable material.
3. the natural home or environment of an animal, plant, or other organism.
4. reuse (discarded objects or material) in such a way as to create a product of a higher quality or value than the original.
6. of, relating to, or derived from living matter.
10. the surroundings or conditions in which a person, animal, or plant lives or operates
12. (of a contract, agreement, etc.) capable of being renewed.
15. a place to dispose of refuse and other waste material by burying it and covering it over with soil, especially as a method of filling in or extending usable land.
16. (of a species, family, or other larger group) having no living members.
18. of, relating to, or determined by the sun.