Across
- 5. complex life form formed after the Earth froze about 200 MYA (9)
- 7. force that pulls matter together (1)
- 8. name of supercontinent that broke apart about 175 MYA (15)
- 10. Earth is 4.5 what years old
- 12. this process began about 3 billion years (4) two words
- 14. the earth’s atmosphere was void of this gas until about 2.4 billion years ago (5)
- 15. first appeared on Earth about 465 MYA (20)
- 16. life may of started near warm alkaline what (2)
Down
- 1. this process made considerable gains about 30 MYA (23)
- 2. first mammals were small and what like (17)
- 3. the end result of photosynthesis (3)
- 4. period where the first reptiles started to appear (14)
- 6. about 1.2 billion years ago organisms started sharing this (7)
- 7. relatives of this were probably the first plants to live on land (11) two words
- 9. what eukaryote cells absorbed what to obtain a new energy source (6)
- 11. period where the first mass extinction occurred (12)
- 13. birds developed from feathered what (19)