Question

nitrogen cycle
atmosphere 78% ammonia proteins denitrifying
nitrate nitrogen - fixing plants animals waste plants

1. our atmosphere is ____ nitrogen gas.
2. animals and plants cannot directly use all the nitrogen found in our ____.
3. only special bacteria can directly use nitrogen in our atmosphere and \fix\ it so other organisms can benefit. these bacteria are called __ - __ bacteria.
4. higher organisms use nitrogen to make their ____.
5. animal waste decay by the action of bacteria which create __ and __ products rich in nitrogen, and useful for plants to use again.
6. ____ bacteria in the soil can break down the ammonia into the gaseous form of nitrogen, which is not available for use by plants or animals.
7. in another part of the cycle, animals eat __ containing nitrogen, which is again returned to the soil by animal or decaying and __.
8. draw a diagram of the nitrogen cycle using the words in the text box.

Explanation:

1. The atmosphere is 78% nitrogen gas.
2. Animals and plants cannot directly use atmospheric nitrogen.
3. Nitrogen - fixing bacteria can fix atmospheric nitrogen.
4. Higher organisms use nitrogen to make proteins.
5. Animal waste decay by bacteria creating ammonia and other nitrogen - rich products.
6. Denitrifying bacteria break down ammonia into gaseous nitrogen.
7. Animals eat plants containing nitrogen, and it is returned to the soil by waste or decaying bodies.
8. To draw the nitrogen cycle, start with the atmosphere having 78% nitrogen. Nitrogen - fixing bacteria convert it for plants. Plants are eaten by animals, which excrete waste. Bacteria act on waste to form ammonia. Denitrifying bacteria convert ammonia back to gaseous nitrogen in the atmosphere.

Answer:

1. 78%
2. atmosphere
3. nitrogen - fixing
4. proteins
5. ammonia; other
6. Denitrifying
7. plants; waste; bodies
8. (Diagram description as above, actual drawing is not possible in text - based response)