West Melbourne School for Science
EXPERIMENTS

"Heads or Tails"

Problem:  Is one end of an earthworm more sensitive to odors?

Materials per pair:
Earthworms
Paper towels
Cotton balls
Fingernail polish

Procedure:

1. Moisten a paper towel.

2. Place several worms on the damp paper towel.

3. Wet a cotton ball with fingernail polish remover.

4. Hold the cotton ball near one end of the worm.

5. How does the worm respond to the odor?

6. Try the other end of the worm.

7. Try this on several other worms.

8. Record your observations in your lab journal and create a chart to record your results.

Results:  Students predicted that since a worm does not have a nose, neither end of the worm would respond to odors.  During the experiment students discovered that no area showed greater sensitivity to the odor on the cotton ball.  The worm makes an effort to move away from irritating smell no matter where the cotton ball is placed.

Conclusion:  Earthworms do not have sense organs that we can see, such as a nose, but they do have a nervous system that responds to stimuli such as odors.  Earthworms have a brain at the front end of the body with a large nerve cord extending all the way to the tail.  Each body segment also contains a mass of nerve tissue that controls activities within each segment.  This is why the worm responds to odors at any place on its body.