Lesson 5.5 - Nitrogen Cycle: Part 2

You have learned that nitrogen is fixed into nitrates by lightning.  There is another way that nitrogen is changed into nitrates.  Special bacteria called nitrogen-fixing bacteria convert nitrogen from the air into nitrates.  These bacteria need a food supply of sugar to live.  Where do they get the sugar? 

A group of plants called legumes include clover, alfalfa, peas, beans, and peanuts. In nodules (lumps) in their roots, the nitrogen-fixing bacteria live and do their work.  The legume plant provides the bacteria with sugar, and in return, the bacteria produce nitrates for the plant.  It turns out that the bacteria produce more nitrates than the legumes can use, so the excess nitrates move into the soil from the roots and are then used by other plants.

Now, answer the following questions.

Question 1. Besides lightning, what is another way nitrates are produced?

Question 2. Where do nitrogen-fixing bacteria live?

Question 3. What are some examples of legumes?

Question 4. What happens to any excess nitrates that nitrogen-fixing bacteria produce?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Besides lightning, what is another way nitrates are produced?

Nitrates are produced by nitrogen-fixing bacteria.

Question 2. Where do nitrogen-fixing bacteria live? 

Nitrogen-fixing bacteria live in nodules in the roots of legume plants.

Question 3. What are some examples of legumes?

Some examples of legumes are clover, alfalfa, peas, beans, and peanuts.

Question 4. What happens to any excess nitrates that nitrogen-fixing bacteria produce?

Excess nitrates that are produced by nitrogen-fixing bacteria are used by other plants. 

 


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