Across
- 4. a colorless and odorless element that makes up most of Earth's atmosphere—the symbol for nitrogen is N
- 6. poisonous, harmful
- 7. areas in water where oxygen levels are so low that aquatic life cannot survive
- 8. a metallic element found in nature and needed by all living things to survive—the symbol for potassium is K
- 9. any of various gases (such as carbon dioxide or methane) that absorb infrared radiation, trap energy in the atmosphere, and contribute to the greenhouse effect
- 11. a rapid growth of tiny aquatic organisms found in water
- 16. the process of dead organisms breaking down into smaller, simpler pieces
- 17. a substance added to soil or sprayed on crops to provide plants with essential nutrients
Down
- 1. a significant difference in the Earth's climate, including warmer temperatures and their associated effects
- 2. a large group of simple organisms similar to plants but without distinct organs and structures
- 3. the requirements a design has to meet to be successful
- 5. a limit or restriction on a design
- 10. a community of living organisms and their environment
- 12. theprocess for describing how nitrogen continually cycles among land, waters, atmosphere, and organisms
- 13. an essential element needed by all living things to survive—the symbol for phosphorus is P
- 14. the removal of oxygen from a substance, like water
- 15. the movement of fertilizer nutrients from soil into bodies of water, caused by irrigations or high rainfall