Grass Decomposition Lab
Background: Saprotrophs, also known as decomposers, are essential in ecosystems. They feed off dead, organic matter in the soil. During this process, they release nutrients back into the soil for the primary producers (plants) to use. The main decomposers in soil are fungi and bacteria.
Purpose: In this lab, students will observe the relationship between moisture level and plant (grass) decomposition. In addition, a comparison will be made between aerobic and anaerobic decomposition.
Hypothesis: Create one (what do you think you will see?)
Materials:
-10 small, clear plastic cups -Plastic food wrap
-Distilled water -rubber bands
-Freshly cut lawn grass -Tape
-Graduated cylinder -Scissors
-Digital Balances
Procedure:
1) Place 5 grams of grass in each of the 10 plastic cups. Make sure to remove all small rocks, leaves, and twigs before massing the grass.
2) Add each of the following amounts of water to the 2 cups: 0 ml, 4 ml, 8 ml, 16 ml, and 64 ml. Label the cups according to how much water they have. Also, put your group name on the cups.
3) After adding the water, cut up small squares of plastic wrap. Place a plastic wrap square on the top of each of the plastic cups, securing them in place with a rubber band around the rim.
4) Take a pin and punch 4 very small holes in just one of each of the following container: 0 ml, 4 ml, 8 ml, 16 ml, and 64 ml. Now you have 2 sets of plastic decomposition cups, one with holes (aerobic) and one without holes (anaerobic).
5) Take each cup and weigh it. Record the weights in Table A. These will be your pre-decomposition weights.
6) Place all the cups together in the same area so as not to introduce extra variables such as temperature and light.
7) Each day you report to class, remass all the cups with the digital balances. Record the data in Table B.
8) Lastly, in the data section, draw 2 graphs, one of aerobic and the other of anaerobic decomposition. The x-axis should be the time in days and the y-axis should be the weight of the cups in grams. Begin with the initial mass.
Data:
Table A: Initial Decomposition Weights of Cups
|
Weights |
0 ml |
4 ml |
8 ml |
16 ml |
64 ml |
|
Aerobic Cups |
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Anaerobic Cups |
|
|
|
|
|
|
Weights |
0 ml |
4 ml |
8 ml |
16 ml |
64 ml |
|
Aerobic Cups |
|
|
|
|
|
|
Anaerobic Cups |
|
|
|
|
|
|
Weights |
0 ml |
4 ml |
8 ml |
16 ml |
64 ml |
|
Aerobic Cups |
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|
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Anaerobic Cups |
|
|
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|
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2) Follow directions in Procedure # 9 for the creation of
the graph.
Conclusion:
Follow the Conclusion Prompt in your Syllabus. Make sure to detail what you observed, was your hypothesis right, and what you believe caused the outcome of this experiment.