Observation of an Earthworm - Loudoun County Public Schools

Worm Handling Grade Name(s) ___________________________________
12 3 4 5

Observation of an Earthworm

1. Place the earthworm on a moist paper towel in a dissecting pan. Observe the worm as it moves.
Describe how it responds to:
a. Being flipped over _________________________________________________________
b. Running into an obstruction. ________________________________________________
________________________________________________________________________

2. What color is the dorsal (back) side? _________________

3. What color is the ventral (stomach) side? _____________

4. Watch the earthworm carefully. One end seems to be more active and leads the other end. This
is how you can tell the anterior (front) from the posterior (back). Also, the clitellum (thickened
band) is closer to the anterior end.

On the image, label the ANTERIOR, POSTERIOR, and CLITELLUM

5. Now that you are familiar with your worm, it is time to give it a name. ____________________

6. Measure the length of your worm in centimeters. Count the number of segments on your
worm. Compare your worm to other worms in the room.

Your Worm Worm 2 Worm 3 Worm 4 Average

Length (cm)
Number of Segments

Longer worms have ________________ segments. (more, or less, or the same)

7. One the ventral side of the earthworm is small bristles called SETAE. Run your finger along the
ventral side. Which area seems to have the most setae? ___________________

Experiment – test the earthworm’s response to touch, odor, and light.

A. Response to Touch (stimulation)
Place a dry paper towel on one side of the pan and a moist paper towel on the other. Stretch the worm so
that it lies across both towels. Observe the earthworm's response. Alternate how the earthworm starts.

Head starts on dry Response (moves toward wet or dry)
Trial 1
Trial 2
Trial 3
Trial 4

Head starts on wet Response (moves toward wet or dry)
Trial 1
Trial 2
Trial 3
Trial 4

B. Response to Odor---Obtain a Q-tip dipped in ammonia or rubbing alcohol. First, wave the Q-tip near
the worm's posterior end. Record the worm’s reaction. Then repeat this process at the anterior end.
Important—Do not touch the worm with the ammonia, it is toxic!

Response

Ammonia anterior
Ammonia posterior

C. Response to Light—Discuss with your partner and develop an experiment to test whether the
earthworm can sense light or dark.

Describe your experiment.

Conduct your experiment and describe your results.

Conclusion (based off your data and observations)
1. Is your worm a vertebrate or invertebrate?
2. What characteristics did you observe that seem to be unique and would help you classify your worm?

3. What phylum of worms does your earthworm belong to?

4. What class of organisms would you say that your worm is most similar too? Explain why you chose
this group.

5. Worms started out as 3 separate phylum and now there over 13! What criteria would you use to
create new phyla of organisms?

Worms are in a very broad category that is not officially classified in any scientific sense. While most worms are
limbless invertebrates, some worms are actually reptiles or amphibians. Many other animals called worms are
simply insect larvae that have yet to metamorphose into their adult stage.

In an attempt to organize different types of worms, three broad classifications have been created. Several
different species of worms are included in each group, but all have some similar qualities. The following are the
three classifications:

 Annelida – This group is probably the most recognized of the three worm classifications. Phylum
Annelida includes some sea worms, but it is mostly comprised of segmented worms such as
earthworms. Earthworms are also an unofficial broad classification of worms. Hundreds of different
worm species in 16 families are considered earthworms. Earthworms are also divided into three
subcategories depending on their ecosystem. Epigeic earthworms live aboveground. Endogeic
earthworms live underground but near the surface. Anecic earthworms live deep underground.

 Nematoda – This phylum of worms includes roundworms, hookworms and threadworms. Many
roundworms are parasites and can cause a variety of problems for people and pets. Threadworms live
on the ground in damp soil, mossy areas or in decaying vegetation. They can also be found in
freshwater and saltwater. Hookworms are also parasites. These worms live in the intestines of animals
and steal the nutrients from their food before it can be absorbed.

 Platyhelminthes – The worms in this group are flat or ribbon-shaped. Some may also be flat and
shaped like a leaf. Many of the species included in this group are parasites, such as tapeworms.
Flatworms are another example of worms in this group. These are leaf-shaped and come in nearly as
many different shapes and sizes as real leaves.