1. The Nitrogen Cycle

2. Write down these questions and answer them in complete sentences.
Quick Write
In this chapter, you will learn about the formation of the Solar System.
Write down these questions and answer them in complete sentences.
1. Why is N important to living things?
2. What percentage of the AS is N?

3. 1. Why do living things need N?
For amino acids needed for proteins.
2. Different forms of N in the biosphere?
N2 gas in atmosphere
NH3 (ammonia)
Nitrate (NO3)
Nitrite (NO2)

4. 3. Nitrogen gas (N2)?
78% of the AS is made up of this gas.
4. NH3, NO2 and NO3?
Found in wastes of many orgs and in dead and decaying organic matter.

5. Movie Check for Understanding Why do living things need N?
N2 gas makes up ___% of the atmosphere What are the 3 other main types of N on Earth?
Movie

6. 5. Nitrogen fixation?
Certain bacteria convert N2 gas into ammonia (NH3). N gets ‘fixed’ into a form plants can use.
6. Then what?
Other bacteria convert NH3 into NO2 and NO3.
7. Why are NO2 and NO3 important?
They help plants grow. Commonly found in fertilizers.

7. 8. Then what?
NO2 and NO3 can be used by plants to make amino acids and proteins.
9. Animals and N?
Consumers use the N from plants to make their amino acids and proteins.

8. Check for Understanding
_____ _____ is the process of converting Nitrogen gas from the atmosphere into a form plants can use.
Ammonia gets converted to ____ or ____, both of which are used for plant growth, production of amino acids, and proteins.
Where do animals get their Nitrogen for their amino acids and proteins?
Movie

9. 10. Denitrification?
Where N fixation is converting N2 gas into NH3, denitrification is the opposite.
11. DN process?
When orgs die, NH3 returns to soil.
12. Then what?
NH3 used by other plants, or bacteria convert back to N2 gas.

10. 13. Other ways N is added to environment?
Excretion by land orgs
Excretion by marine orgs
14. Excretion?
NH3 is found in urine and solid wastes produced by organisms.

11. Check for Understanding
Denitrification is the process where ____ is converted back to ____ and released to the AS.
What is another process where Nitrogen is added to the environment by land and marine organisms?