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Across 1. the total amount of living matter in a given unit area 7. the organic phenomenon of rotting 9. synthesis of compounds in plants aided by radiant energy 10. the strength of a solution 12. a colorless odorless gas used as a fuel 13. the regions of the Earth where living organisms exist 16. a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis 17. fuel consisting of the remains of organisms preserved in rocks in the earth's crust with high carbon and hydrogen content 20. 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 23. a salt or ester of nitrous acid (converted to nitrates during nitrogen cycle). 25. the state of being clear of trees 26. the bodily process of inhalation and exhalation 31. a salt or ester of nitric acid (can be used by plants and passed on to consumers 33. live on plants roots in a mutalistic relationship in which they give plants nitrogen in return for carbohydrates 34. warming when solar radiation is trapped by the atmosphere 35. bacteria that decay decaying animals and their urine to obtain ammonia. 36. matter that has been deposited by some natural process

Down 2. the mass of air surrounding the Earth 3. the watery layer of the earth's surface 4. an organic compound containing only carbon and hydrogen 5. of or relating to living organisms 6. when the amino acid in urine/decaying animals is converted into ammonia 8. a substance that is released 11. 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 14. a periodically repeated sequence of events 15. bacteria that turn nitrates back into nitrogen gas anaerobically. 18. the remains of a plant or animal from a past geological age 19. a gas that contributes to the greenhouse effect by absorbing infrared radiation 20. a change in the world's climate 21. the process of becoming acid or being converted into an acid 22. the part of the Earth consisting of the crust and mantle 24. an abundant nonmetallic element in all organic compounds 27. a reaction of a substance with oxygen to give heat and light 28. movement of a substance from an area of high concentration 29. a colorless, odorless gas that is essential for respiration 30. the solid part of the earth consisting of the crust and outer mantle 32. gaseous elements that constitutes about four-fifths of the atmosphere.