Science puzzle

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Across
  1. 4. wall a rigid structure of a cell provides shap and protection
  2. 5. the process of the chemical activities digestion
  3. 6. organisms that eat other living things
  4. 7. a structure with a specialized function within a cell
  5. 9. organisms that obtain their food by decomposing dead things
  6. 10. the nonliving things in an environment
  7. 11. a change in an environment
  8. 13. a substance that is made up of one type of atom
  9. 17. a critical chemical of life that builds proteins
  10. 18. a critical chemical of life that is made up of fats and oils
  11. 21. a group of organisms that make their own food
  12. 22. a critical chemical of life that builds cells
  13. 23. cell division of prokaryotic cells
  14. 24. the living things in an environment
  15. 25. a basic unit of life
Down
  1. 1. the control center of a eukaryotic cell
  2. 2. cell without a nucleus
  3. 3. a critical chemical of life that is used in the body for energy
  4. 4. an organelle that absorbs sunlight and uses it to make food (sugar)
  5. 8. theory that other living things come from other living things
  6. 12. when a stimulus is too severe
  7. 14. how cells with a nucleus divide
  8. 15. the smallest part of an element
  9. 16. the maintenance of a constant internal state in a changing environment
  10. 19. the process of changing to an environment
  11. 20. cells with a nucleus and membrane