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Across 6. the metabolic processes whereby certain organisms obtain energy from organic molecules; processes that take place in the cells and tissues during which energy is released and carbon dioxide is produced and absorbed by the blood to be transported to the lungs 7. warming when solar radiation is trapped by the atmosphere 8. a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis 9. synthesis of compounds in plants aided by radiant energy 10. the strength of a solution 12. when the amino acid in urine/decaying animals is converted into ammonia 14. the organic phenomenon of rotting 16. the state of being clear of trees 17. movement of a substance from an area of high concentration 18. a change in the world's climate 22. live on plants roots in a mutalistic relationship in which they give plants nitrogen in return for carbohydrates 23. the solid part of the earth consisting of the crust and outer mantle 28. an organic compound containing only carbon and hydrogen 32. a substance that is released 34. a colorless odorless gas used as a fuel 35. the mass of air surrounding the Earth 36. matter that has been deposited by some natural process 37. a periodically repeated sequence of events

Down 1. of or relating to living organisms 2. an abundant nonmetallic element in all organic compounds 3. bacteria that turn nitrates back into nitrogen gas anaerobically. 4. the process of becoming acid or being converted into an acid 5. bacteria that decay decaying animals and their urine to obtain ammonia. 11. a gas that contributes to the greenhouse effect by absorbing infrared radiation 13. fuel consisting of the remains of organisms preserved in rocks in the earth's crust with high carbon and hydrogen content 15. the action of forming a chelate or other stable compound with an ion or atom or molecule so that it is no longer available for reactions 19. the part of the Earth consisting of the crust and mantle 20. a salt or ester of nitrous acid (converted to nitrates during nitrogen cycle). 21. the bodily process of inhalation and exhalation 24. a reaction of a substance with oxygen to give heat and light 25. the watery layer of the earth's surface 26. the remains of a plant or animal from a past geological age 27. the total amount of living matter in a given unit area 29. the regions of the Earth where living organisms exist 30. a salt or ester of nitric acid (can be used by plants and passed on to consumers 31. gaseous elements that constitutes about four-fifths of the atmosphere. 33. a colorless, odorless gas that is essential for respiration