Name: _______________________________
Observation of the Planaria
The Planaria is a freshwater flatworm. It is found in the rocky muck at
the bottom of rivers, streams and lakes. It’s a scavenger that feeds on things
that float down from above. Answer the questions below that require a live Planaria for
observation. Then, identify the parts the Planaria on the reverse side of this page.
1.
Transfer a Planaria from the central jar, to the petri dish with the soft bristled
paintbrush. This will prevent damage to the tissue. Now, look carefully at the Planaria under the
stereomicroscope. Describe its movements. What structures does it use to move? (you may
want to look at the diagram on the reverse, far right side of this page. Also read pages 690-691
and read the notes I handed out in class)
2. Create a gentle current of water in the dish with the paintbrush. How does the Planaria
react?
3. Change the light settings of your stereomicroscope and observe any changes in the behavior
of the Planaria. How would you describe the Planaria’s response to light?
4. Using the tip of the paintbrush, gently touch rear end of the Planaria. Now, touch the head
end. Is there any difference in how it responds? Would you expect a difference? Why or why
not?
5. Turn the Planaria over with the white spatula, and find its mouth about halfway down the
belly side. How does the Planaria react when you flip it over?
6. Define the word cephalization (pronounced “sef-ill-i-zay-shun”). See the glossary of your
text. What evidence is there that the Planaria shows cephalization?
7. The Planaria, like all flatworms has an incomplete digestive system and no circulatory system.
Explain how food gets to all portions of the Planaria. (refer to the notes I gave you and diagram
“b” on the back side of this)
To help you with this activity, you should look at the portion of your notes that say:
“Key Terms for Body Locations”. In addition use the diagrams that are found on pg.690 of your
text, and on the bottom left hand corner of this sheet.
On the ventral view of the Planaria, showing the digestive and excretory structures, label
the following: anterior end, posterior end, anterior intestine, pharynx, mouth, lateral
intestine,flame cell,eyespots. (use diagram letter “b” below to help you)
On the dorsal view, showing the nervous and reproductive systems, label the following:
brain, longitudinal nerves, transverse nerves, lateral nerves. (use diagram letter “a” below)
On the cross sectional view, label the ectoderm, endoderm, mesoderm and cilia.
Ventral View
Dorsal View
Cross Section View