Chapter 6.1

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Across
  1. 3. first living organism made of a single cell
  2. 4. layer, protects Earth from harmful radiation from the sun
  3. 8. earliest animals that developed from bacteria
  4. 9. plant parts that absorb water from the ground
  5. 10. place where the first life originated
  6. 11. process where organisms use energy from the sun
  7. 13. soft material that some fish skeletons are made of
  8. 14. organisms made of more than one cell
  9. 16. first vertebrates that lived on land
Down
  1. 1. extinct group of animals that once dominated Earth
  2. 2. animals that feed their young with milk
  3. 5. animals with hard-shelled eggs that survive without water
  4. 6. first animals that moved onto land
  5. 7. a living being
  6. 12. animals with a backbone like fish
  7. 15. place where plants and later animals spread to