Earthworm Science

Investigation #2: Earthworms in Action

As earthworms burrow through the soil, they consume large quantities of soil and fresh or partially decomposed organic matter from the soil surface. Earthworms deposit fecal matter (casts) throughout and on top of the soil. As earthworms travel up and down and through out the soil, they mix soil from the different soil layers with plant and animal debris from the soil surface. This mixing helps to make more nutrients available for plant growth, and helps to create a better soil habitat for all soil organisms.

What do earthworms do to the layers of soil?

Make a prediction about the things earthworms do in soil.

• Always construct your bottle ecosystems with the help of an adult.
• Be careful with sharp objects.
• Wash your hands when you are finished this activity.

• Always treat earthworms with dignity and respect.
• Keep earthworms moist at all times.
• Limit the number of times that you handle or touch your earthworms.

• 2 - 2 litre pop bottle ecosystems [Click here for the instructions]
• Tools required to construct your pop bottle ecosystems

• Gravel
• Sand (do not use Perlite)
• Bedding material
• Dark potting soil
• 2 pie plates
• 2 pieces of tin foil or dark coloured construction paper

1. Construct two pop bottle ecosystems for your earthworms. [Click here for detailed instructions on how to prepare a pop bottle ecosystem.]
2. Add the following components to the bottom of each ecosystem in order:

   

   1. add some clean, washed gravel to the bottom of the bottle
   2. add a layer of moist bedding material
   3. place a layer of dark potting soil on the moist bedding material

      

   4. add a layer of moist sand

      

   5. add another layer of dark potting soil

      

      Your bottle ecosystem should look similar to the ones shown below.

      

   6. add a thin layer of organic matter (food)

      

3. Depending on the size of the worms, add three or four earthworms on top of the organic matter in ONE of the bottle ecosystems. Leave the other as a control for your experiment.

   

4. Draw a picture or take a digital photograph of your ecosystems.

   

5. Tape the tops back onto the bottle using masking tape.

   

6. Form the tin foil around the bottle ecosystem to limit the amount of light that reaches the worms. Make sure air can get in through the top of the pop bottle.

   

7. Place the ecosystems on the pie plates and place at room temperature or a bit cooler (15 to 22°C). Do not place them in direct sunlight (remember earthworms are very sensitive to the light).
8. Check your bottle ecosystems every day. Make sure that you:
   1. moisten the soil
   2. add more moistened food to the top layer if necessary
   3. observe your ecosystems and record your observations
   4. draw a picture or take a digital photograph of your ecosystems

1. What happens to the organic matter on the surface of the ecosystem with earthworms?
2. What happens to the organic matter on the surface of the ecosystem without earthworms?
3. Describe what earthworms do to the soil.

1. Why are earthworms considered to be decomposers?
2. Based on your observations, what benefits do you think earthworms have for a soil ecosystem?
3. What is the purpose of the ecosystem that does not have any earthworms added?