B12

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Across
  1. 2. Smallest unit of an element
  2. 4. Pure substance made of one type of atom
  3. 7. Natural environment of an organism
  4. 9. Anything with mass and volume
  5. 10. All populations living together
  6. 11. Living and nonliving things interacting
  7. 13. All ecosystems on Earth
  8. 14. Role of an organism in its ecosystem
  9. 15. Force holding atoms together
Down
  1. 1. Members of one species in an area
  2. 3. Ability to do work
  3. 5. Two or more atoms chemically joined
  4. 6. Element forming the basis of life
  5. 8. Essential molecule for life
  6. 10. Substance made of different elements
  7. 12. Organisms capable of producing fertile offspring