Earth Day

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Across
  1. 5. Able to be maintained
  2. 8. Trash that is left lying in public places
  3. 10. Part of biology that deals with the relationships of organisms and how they relate
  4. 12. The layer of gas that surrounds the Earth
  5. 13. An area trash is disposed of
  6. 14. A population that has no living members left
  7. 16. Relating to living matter
  8. 18. Maintain something in its original state
  9. 20. A gas that protects us from harmful UV radiation
Down
  1. 1. A biological community where organisms interact
  2. 2. Reusing discarded material to make it into a product of higher value
  3. 3. To contaminate something with a toxic substance
  4. 4. Discharge of gas or radiation
  5. 6. The surroundings in which an organism lives
  6. 7. Can be used without running out
  7. 9. Convert trash into useful material
  8. 11. The natural home or environment of an organism
  9. 15. Prevent something from being harmed
  10. 17. Decayed material used for fertilizing plants
  11. 19. Relating to the Sun