Question

directions: match the definition in the left column with the word it identifies from the column on right.

1. ____ the circulation of nitrogen and its compounds by living organisms in nature.
2. ____ one - celled microscopic plants used in the process of nitrogen fixation.
3. ____ substance which makes up living cells.
4. ____ two or more elements chemically combined.
5. ____ a gaseous element that forms about 3/4 of the atmosphere and is in animal and plant matter.
6. ____ process of reducing elements in the soil to gaseous nitrogen by bacteria.
7. ____ any plant of the pea family which absorbs nitrogen from the air and, by means of bacteria, converts it to a useable form.
8. ____ complex organic compounds combined to form proteins that make up living matter.
9. ____ layers of gases that surround the earth; the air.
10. ____ made of hardened remains of once - living things.
11. ____ swellings on roots containing bacteria necessary for nitrogen - fixing.
12. ____ converting atmospheric nitrogen into nitrates, a useable form for plants.
13. ____ contaminated rainfall.

a. acid rain
b. atmosphere
c. protoplasm
d. nitrogen cycle
e. amino acids
f. bacteria
g. compound
h. nitrogen
i. denitrifying
j. nodules
k. legumes
l. nitrogen - fixing
m. fossil fuel
the nitrogen cycle

Explanation:

Each definition is matched to its corresponding term based on biological and environmental science terminology related to the nitrogen cycle and basic life sciences.

Answer:

1. D. nitrogen cycle
2. F. bacteria
3. C. protoplasm
4. G. compound
5. H. nitrogen
6. I. denitrifying
7. K. legumes
8. E. amino acids
9. B. atmosphere
10. M. fossil fuel
11. J. nodules
12. L. nitrogen-fixing
13. A. acid rain