Name: ____________________ ______________ Block: ________ Date: _________________________
Earthworm Dissection Lab
Biology 11
Note: Your dissection will be worth 10 points.
Purpose: You are responsible for writing your own purpose.
Procedure: Follow these steps carefully, as your dissection will be marked.
1. Rinse the worm in water.
2. Cut the worm just posterior to the clitellum.
3. Place the two sections in the dissection tray, dorsal side up.
4. Use the posterior section to practice cutting the dorsal side of the earthworm. This will allow
you the opportunity to learn how deep to cut without cutting the internal organs of the worm.
5. Using the anterior section, use a scalpel to make a shallow cut from the clitellum to the
prostomium.
6. Place the pins at a wide angle about every 5th segment to spread the body wall.
7. Locate and identify the structures on the labeled diagram on back of this sheet.
Materials: List all the materials used in this lab.
Observations:
Observe the slide of the earthworm cross section (C.S.) under low power. Draw a diagram and label as
completely as possible. Identify: intestine, coelom, ventral nerve cord, dorsal blood vessel, nephridia.
Discussion:
1.
From the C.S. you observed, how can you distinguish between the dorsal and ventral side of the
worm?
2. (a) List all of the parts involved in the worm’s reproductive system and give the function each
part carries out.
(b) Describe the mating and egg-laying process of the earthworm. What is the function of the
clitellum?
(c) Why do you think that the earthworm evolved such a complex system for reproduction?
3. (a) List all of the parts involved in the earthworm’s digestive system and give the function each
part carries out.
(b) Explain how the earthworm ingests and digest its food.
4. (a) How does the earthworm survive without a specialized respiratory system?
(b) How does this system limit the worm’s lifestyle?
5. Briefly describe these systems in the earthworm.
(a) the nervous system
(b) the excretory system
(c) the circulatory system
Name: ____________________ ______________ Block: ________ Date: _________________________
Conclusion:



Why did you cut the dorsal side of the earthworm?
If you cut an earthworm in two if it is alive, would it perform any special reproductive process?
Explain.
Give two evolutionary developments the earthworm has that the flatworm does not.