Science

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Across
  1. 3. other organisms use sunlight to
  2. 5. mantle.
  3. 7. colourless, odourless unreactive gas that
  4. 8. the chemical element of atomic number 7,
  5. 12. a biological community of interacting
  6. 15. between two glacial periods.
  7. 17. The official procedure or system of rule
  8. 18. relating to a period of milder
  9. 20. about 78 percent of the earth's
  10. 21. the action of breathing.
Down
  1. 1. capital of Japan
  2. 2. a thick subsurface layer of soil that
  3. 4. and their physical
  4. 6. affairs of state or
  5. 9. year, occurring chiefly in polar regions
  6. 10. of the crust and
  7. 11. below freezing point throughout
  8. 13. occasions.
  9. 14. the process by which green plants and
  10. 16. any accumulation of unconsolidated debris
  11. 19. the rigid outer part of the earth,