Air, Soil and Food chains

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Across
  1. 4. this gas is found in fluorescent tubes
  2. 5. if I eat the animal that eats the plant, what level am I?
  3. 7. the release of energy from food
  4. 9. we make our own food
  5. 10. used to break down dead material and return nutrients to the soil
  6. 13. the only type of plants with nitrogen fixing bacteria in their roots
  7. 14. makes the soil very fertile
Down
  1. 1. humans fall in this category because we eat both plants and meat
  2. 2. carbon gas is returned to the environment by this process
  3. 3. this type of soil holds a lot of water
  4. 6. dry ice
  5. 8. the same amount of this gas we breathe in is the same amount we breathe out
  6. 11. roots of trees grow into this layer
  7. 12. makes your voice squeaky