Across
- 4. Underground rock layer that stores water
- 6. Nutrient buildup in water causing algal blooms
- 7. Harmful compounds that destroy the ozone layer
- 8. First species to colonize bare land
- 10. Organisms interacting with each other and their environment
- 13. A group of organisms of the same species in one area
- 14. Non-living components of an ecosystem
- 18. Index used to estimate population size
- 19. Long-term weather patterns of an area
- 20. All populations living together in an area
Down
- 1. Planting trees again in an area where forests were removed
- 2. Growing one crop over a large area
- 3. The variety of species in an ecosystem
- 5. Gradual change in ecosystems over time
- 9. Layer of atmosphere that blocks UV radiation
- 11. Using resources without harming future generations
- 12. Relationship between dependents and working-age population
- 15. Fuels made from biological material
- 16. Living components of an ecosystem
- 17. Thick polluted air caused by sunlight reacting with pollutants