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1.2 Nutrient Cycles and Energy Flow
© Pearson Education
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Across
4. A large portion of the matter in a tree is made of the element, _____, and all of it came from the atmosphere.
7. Humans obtain the _____ they need from eating proteins.
9. In the atmosphere water exists as a gas called water _____.
10. The world’s _____ are biotic reservoirs of carbon.
11. _____ usually enters the ecosystem as sunlight and leaves it as heat.
13. The process of producing carbohydrates from carbon dioxide, water and sunlight is called _____.
14. Some ground water may flow into large underground lakes, known as _____.
15. Nutrients are made up of _____, which are pure substances that cannot be broken down into simpler substances.
19. Nitrogen cannot be used directly by most _____.
21. Nitrogen-fixing _____ convert nitrogen gas into ammonia.
22. Nitrifying bacteria convert _____ into nitrites, and then nitrates, which plants absorb through their roots.
23. Denitrifying bacteria in the soil convert _____ back into nitrogen gas, which returns to the atmosphere.
24. Besides bacteria, _____ is the only other natural nitrogen-fixing process.
Down
1. _____ occurs when plants release water vapour into the atmosphere through their leaves.
2. The process of moving a nutrient back and forth is called a nutrient _____.
3. Any place where matter accumulates is called a _____.
5. In the water cycle, water is moved throughout the whole _____.
6. As water vapour in the atmosphere cools, it condenses to form _____.
7. _____ are substances that an organism uses to build and repair the cells of its body.
8. Because oil and gas were formed so long ago, they are called _____ fuels.
12. When animals digest proteins a byproduct is ammonia, which is _____.
16. Plants called _____ (peas, beans, and alfalfa) have nodules on their roots that house nitrogen-fixing bacteria.
17. All organisms need nitrogen to make _____.
18. Converting nitrogen gas into ammonia is called nitrogen _____.
20. _____ (which is almost pure carbon) and oil deposits were formed from the remains of huge forests that lived hundreds of millions of years ago.