Across
- 1. mixture of gases that surrounds Earth
- 5. aquatic plant that includes seaweed
- 7. pigment that gives plants their green color
- 8. water-based environment
- 9. microscopic marine algae
- 10. the solid earth
- 12. colorless, odorless gas; exhaled by humans and used by plants during photosynthesis
Down
- 2. the total amount of water on the planet
- 3. the process by which plants use energy from sunlight to make food
- 4. the amount of salt in water
- 6. a microscopic organism floating in the sea or freshwater
- 11. region of the Earth that includes all living organisms (plants, animals, bacteria)