Across
- 3. Gradual change in species over time.
- 7. Proposed explanation made on the basis of limited evidence.
- 9. Subatomic particle with no electric charge.
- 11. Substance that increases the rate of a chemical reaction.
- 12. Variants of a particular chemical element with different neutron numbers.
- 15. Powerhouse of the cell, where energy production occurs.
- 16. Community of living organisms interacting with their environment.
- 17. Substance that stimulates the immune response to prevent disease.
- 19. Smallest unit of a chemical element.
- 20. Large naturally occurring community of flora and fauna.
Down
- 1. Study of heredity and variation in organisms.
- 2. Force that attracts objects toward each other.
- 4. Protein that speeds up chemical reactions in living organisms.
- 5. Process by which plants make food using sunlight.
- 6. Visible surface of the sun.
- 8. Set of life-sustaining chemical reactions in organisms.
- 10. Instrument for observing distant objects.
- 13. Fundamental particle making up protons and neutrons.
- 14. Combination of two or more atoms bonded together.
- 18. Thread-like structure carrying genetic information.