Nutrient Cycles

2. Another source of phosphorus can come from human interference called man-made __.
4. Natural gas, oil, and what deposits are burned as fossil fuels today?
6. Plants use CO2 to do this process to make sugar and oxygen.
10. This is another natural source of CO2.
12. Animals and plants cannot directly use all of the nitrogen found in our ___.
15. This bacteria in the soil can break down the ammonia into the gas form of nitrogen which is not available for us by plants or animals.
16. Some of the phosphorus in soils can be washed away into what body of water?
18. Too much CO2 in the atmosphere leads to this effect.
19. What part of earth is the main regulator of CO2?
20. Higher organisms use nitrogen to make their what?

1. The special type of bacteria able to use nitrogen directly.
3. After the plants are eaten by animals, they are put into ___ products as sulfur.
5. Found in rocks and minerals.
7. Phosphorus moves between the soil and what?
8. This organism can eat plants containing nitrogen, which is returned in waste.
9. Animals use oxygen to do this process to make more CO2
11. 78% of our atmosphere is made of this gas.
13. Special bacteria can directly use nitrogen and ___ it so other organisms can benefit from it.
14. Phosphorus is essential for life, it also makes up an important chemical called ____.
17. Too much phosphorus in the water leads to plant ___, making no room for all other life forms in the water.