Name: ___________________ ____________________ Block: _________ Date: ________________________________
Planarian Lab
Phylum Platyhelminthes
Purpose: To observe how planarians respond to external stimuli.
Procedure:
1. Observe your worm using the dissecting microscope. Sketch the planarian and
label the eyespots, anterior end, and posterior end.
2. Measure the planarian. This operation is best performed by removing some of the
water from the dish and waiting for the worm to stretch out. Measure the length of
the worm in millimeters. Record your answer next to your drawing.
3. Observe the planarian for about five minutes. Does the planarian seem active or
passive? How does it move? Does it swim or creep? Where in the dish does it spend
most of its time? Record your answers in the table under observations.
4. Make a current in the water with a pipette. How does the planarian react? Record
your answers in the table under observations.
5. Planarians actually display a “handedness” being right or left handed. You can
discover whether your worm is right or left handed by flipping the planarian over on
its dorsal (back) and seeing which way it discovers. If it rolls to the right, it is righthanded. If it rolls to the left, it is left-handed. Record your answer in the table
under observations.
6. When all students have completed the first 4 steps, the lights in the class will be
turned off. Your microscope must be off also. Turn on the bottom light of your
microscope and record the planarian reaction. Turn off the light and then use the
top light; record your observations in the table.
Materials:
List the materials used in this part of the lab.
Observations:
There will be one diagram for this part of the lab. Be sure it is done in a Petri dish and in
pencil. Redraw and complete the following table in your write-up.
Description
Movement
Worm Location
Reaction to current
Handedness
(Other observations)
Name: ___________________ ____________________ Block: _________ Date: ________________________________
Discussion:
1. Explain a possible advantage of the planarian’s response to light.
2. Explain how a planarian might find prey even though its eyespots do not form images.
3. Regeneration is universal among animals. Explain the difference in degree of
regeneration between planarians and humans.
4. Compare the organization of sense receptors in planarians and in humans. How are they
similar?
5. Identify the kingdom, phylum and class that your worm belongs to.
Conclusion:
The conclusion must include your observation for “handedness” as well as an explanation
for why your worm moved like this. Give at least 2 reasons for your worms response.
Include a description of 2 or more experiments that you think could be performed on the
planarian?