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.

1. higher organisms use nitrogen to make their ____________.
2. animal waste decay by the action of bacteria which create ____________ and

__________ products rich in nitrogen, and useful for plants to use again.

1. ______________ 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.

1. in another part of the cycle, animals eat ____________ containing nitrogen, which is

again returned to the soil by animal __________ or decaying __________ and
____________.

1. draw a diagram of the nitrogen cycle using the words in the text box.

Explanation:

The questions test key concepts of the nitrogen cycle, using terms provided in the text box. Each blank is filled with the appropriate term from the given list based on nitrogen cycle processes.

Answer:

1. 78%
2. atmosphere
3. nitrogen-fixing
4. proteins
5. ammonia; nitrate
6. denitrifying
7. plants; waste; plants; animals
8. (Diagram: Atmosphere (78% N₂) → nitrogen-fixing bacteria → ammonia/nitrate → plants → proteins → animals → waste → ammonia/nitrate → denitrifying bacteria → atmosphere)