Across
- 1. The primary element in the present-day atmosphere
- 3. Oxygen levels INCREASED or DECREASED during the Proterozoic (pick one)
- 5. The oldest rocks on Earth, found in Canada (2 words)
- 7. Block of geologic time, during which continental crust formed
- 11. Largest chunk (88%) of geologic time
- 12. Unit of heredity, found in pairs and control traits
- 15. Early Proterozoic landmass that contained North America
- 17. Type of bird used by Darwin to demonstrate ideas of natural selection
- 20. The process by which life was able to arise on Earth
- 22. One of the two requirements for “life”
Down
- 2. Type of rock formations characterized by lower volcanic/metamorphic rocks, topped by sedimentary rocks
- 4. Ediacaran fossils lacked hard ________, making it hard for them to be fossilized
- 6. Human beings are complex cellular beings called _________.
- 8. Eon during the Precambrian during which organisms first appeared
- 9. The cycle that explains the opening and closure of ocean basins
- 10. One of the two requirements for “life”
- 13. Populations of organisms that can interbreed and reproduce
- 14. Type of selection that favors individuals that can best adapt to their environment
- 16. The first documented supercontinent
- 18. Type of evolution mixing newly evolved and ancestral characteristics
- 19. Type of evolution where unrelated organisms develop similar features
- 21. Largest eon of the Precambrian