Study Guide – Soil Unit Exam

Field Biology

There will be a unit test over soil ecology on Friday, April 4. Please use this study guide to help you prepare for the test. You should have this assignment completed by the beginning of class on Thursday, April 3 – please bring it with you in printed or hand-written format (you will not have time to print your work during class).

1. Why are soil organisms important to the ecological health of plants growing in the soil?

2. What is the importance of the nitrogen cycle? What role do soil organisms play in the nitrogen cycle?

3. Explain how soil organisms can contribute to the decomposition of organic material at the surface of the soil.

4. Why is it that plants can use nitrogen in the form of ammonium (NH₄⁺) and nitrates (NO₃^-) but not organic nitrogen?

5. A chunk of soil is removed from the back seat of Mr. Bregar’s car and placed in a glass beaker. The mass of the soil and the beaker together is 425 grams. The soil is dried for two days in a drying oven; after it has dried, the mass of the soil and the beaker together is 388 grams. The mass of the beaker alone is 78 grams. What is the water content of this soil?

6. Why is it so critical to bleach all of the instruments used during the process of transferring soil bacteria to Petri dishes?

7. What is “soil permeability” and why is it an important soil characteristic to understand?

8. What is “soil texture”? How can you determine soil texture by making measurements and using a soil texture triangle? What information does soil texture tell us that might be useful to know?