The Nature of Crosswords

2. The process in which green plants use sunlight to create energy
4. A dry area on which little rain falls
6. The seasonal movement of animals from one region to another
9. A cascade of water dropping from a height, often found in a scenic spot
12. A community of living organisms interacting with their physical environment
13. A mountain or hill with an opening from which lava erupts
16. The preserved remains or traces of an organism from the remote past
17. The practice of protecting and preserving the natural environment
18. A dense area filled with trees and wildlife
20. A massive, slow-moving body of ice found in cold or elevated regions

1. The process by which pollen is transferred to plants
3. A large, open area of grassland, often found in the central regions of continents
5. A natural flowing watercourse, usually freshwater
7. A field of grass and wildflowers, often used for grazing
8. The ability of an animal to blend into its surroundings to avoid detection
10. The variety of plants and animals that live in a particular place
11. The natural environment where a plant or animal normally lives
14. A high, steep landform rising prominently above the surrounding land
15. A vast, flat, treeless Arctic region where the subsoil is permanently frozen
19. A naturally formed underground chamber, sometimes large enough for a person to enter