Across
- 3. division of earths history.
- 6. 3rd longest time period.
- 9. longest time period.
- 10. era of recent life 66mil years ago.
- 11. Changing in hereditary Features.
- 13. the age of something compared with others.
- 14. second longest time period.
- 15. principle stating that earth's process.
- 17. chlorophyll-containing photosynthetic bacteria.
- 19. thin film residue.
- 20. gap in the rock layer that is due to erosion.
- 21. longest part of earths history 4bilyears.
Down
- 1. can found by properties from atoms.
- 2. era of ancient life.
- 4. middle era of earths history.
- 5. group of organisms.
- 7. remains of a species that existed.
- 8. Process in which isotopes break down.
- 12. time for half atoms of the decay.
- 16. type of body fossil.
- 18. organism with a 3 lobed exoskeleton