Across
- 4. able to be maintained at a certain rate or level
- 5. a natural resource or source of energy that is not depleted by use
- 7. the natural home or environment of an organism
- 12. our surroundings
- 13. rubbish such as paper, cans, and bottles left lying in an open or public place
- 14. convert (waste) into reusable material
- 15. the production and discharge of something, especially gas or radiation
- 17. a biological community of interacting organisms and their physical environment
- 18. the branch of biology that deals with the relations of organisms to one another and to their physical surroundings
- 19. contaminate
Down
- 1. reuse (discarded objects or material) in such a way as to create a product of higher quality or value than the original
- 2. produced without the use of artificial chemicals
- 3. a colourless unstable toxic gas with a pungent odour and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light
- 4. relating to or determined by the sun
- 6. no longer in existence
- 8. the disposal of waste material by burying it
- 9. protect from harm or destruction
- 10. maintain in its original or existing state
- 11. the air in any particular place
- 16. decayed organic material used as a fertilizer for growing plants