Here is a photo of four of the test tubes one week after starting the experiment:
The first test tube on the left (Test Tube 1) has the humus layer of soil in it.
The second test tube (Test Tube 2) has the mineral layer of soil in it.
The third test tube (Test Tube 3) has the bedrock layer of soil in it.
The last test tube on the right (Test Tube 4) has no soil in it.
- Write an observation for each test tube. List each one separately with a separate observation for each of the four.
- What does each observation tell you about the amount of CO2 produced in each test tube? Again, list all four test tubes in your answer.
- What conclusion can you write about the amount of living organisms in each layer? Is there a little, a lot, none?
- The last test tube has no soil in it. Write an observation for this test tube. What is the reason for using this test tube in the experiment?
- What is the importance of this last test tube? What does it prove?
- Is there exactly the same amount of soil in each test tube? How might that affect the experiment? What could we do to prevent such a problem?
This page was last updated on October 6th, 2002.