Across
- 2. dating the exact year
- 4. fossil a fossil useful for dating
- 8. Horizontal layers of rock
- 9. remains of prehistoric organism
- 10. structures look the same but different function
Down
- 1. record fossils from earlier periods
- 3. modification of an organism
- 5. amount of variation
- 6. structures functionless
- 7. structures look different but same function