Across
- 4. The process by which species change over generations
- 5. A protein produced by the immune system to fight pathogens
- 8. Our galaxy, named aptly for its appearance
- 9. The ratio of a circle’s circumference to its diameter
- 12. The chemical formula for water
- 13. The basic working unit of the brain
- 14. Large sections of Earth’s crust that move and cause earthquakes
Down
- 1. The only metal that is liquid at room temperature
- 2. The molecule that carries genetic instructions in living things
- 3. Plants use this process to convert sunlight into energy
- 6. This force keeps planets in orbit and apples on the ground
- 7. A region in space where gravity is so strong that not even light can escape
- 10. This gas forms a protective layer in Earth’s stratosphere
- 11. The most abundant gas in Earth’s atmosphere