Respiration in organisms

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Across
  1. 1. 2nd level of classification
  2. 4. 3rd level of classification
  3. 7. 6th level of classification
  4. 10. Another word for breathing
  5. 11. The creator of this crosswords name (4 letters)
  6. 12. 7th level of classification
Down
  1. 2. An acronym on living creatures
  2. 3. 1st level of classification
  3. 5. The way living organisms feel changes around them
  4. 6. 5th level of classification
  5. 8. 4th level of classification
  6. 9. The way humans expand and get taller and stronger