Natural Cycles

4. the process that releases nitrogen from the soil back into the atmosphere
6. a plant that hosts nitrogen-fixing bacteria
8. the basic building block of matter
9. precipitation that flows over the surface of the soil
11. the process in cells by which oxygen and glucose are used to produce energy and carbon dioxide
13. two or more atoms joined together
15. the process by which precipitation is gathered into a body of water
16. the change of a gas into a liquid
18. meaning earth
19. the cycling of chemical elements through the living and nonliving parts of an ecosystem
20. the conversion of nitrogen in the atmosphere to a form that can be used by plants
21. evaporation of excess water from a plant
22. the precipitation that is more acidic than normal rainwater

1. a source of energy formed from dead plants and animals
2. the brown smog produced when air pollutants react with sunlight
3. the process that allows green plants to make sugars from sunlight, water, and carbon dioxide
5. a swelling on a plant root that contains nitrogen-fixing bacteria
7. the change of a liquid into a gas
10. meaning life
12. a pollutant released into the atmosphere
14. a substance that is made of only one type of atom and cannot be broken down
17. a molecule that consists of two or more different elements
23. a form of water that falls from the atmosphere