Across
- 2. animals breathing out
- 5. what happens with too much CO2
- 7. breathing
- 9. burning fossil fuels could increase this
- 10. how carbon dioxide moves through a plant
- 12. when animals and plants die this happens
- 13. a gas that keeps Earth warm
Down
- 1. plants take this gas in from the air
- 3. burning
- 4. are animals and plants connected to each other
- 6. used by underwater animals to take in dissolved oxygen
- 8. animals taking in air
- 11. animals need this gas to survive