worm lab outline

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Name: ____________________________
Date: ______________
Pd: _____
Worm Dissection Lab
I.
II.
Purpose
The purpose of this lab is to observe the structure and function of internal organs of
earthworms.
Materials
 1 earthworm
 1 dissection tray
 1 pair of dissection
scissors
 1 pair of forceps
 8 t-pins
III.
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.



1 bent probe
1 ruler
1 piece of paper towel

1 pair of
gloves
Observe the external features first
Count the number of segments between the mouth and the clitellum and record.
Measure the length of your worm from mouth to anus in cm and record.
Place a pin through the mouth
Place a second pin behind the clitellum
Make a gentle cut behind the clitellum (NOT TOO HARD)
Take the scissors and lift and cut the top layer of skin. Cut 2cm
Pin open the layers of skin
Continue cutting and keep lifting all the way to the mouth
Pin apart the skin so you can see clearly inside of the earthworm
Draw what you see inside and label the diagram (Use a plain white piece of paper)
a. Aortic arches (hearts)
b. Esophagus
c. Crop
d. Gizzard
e. Seminal vesicles
f. Intestine (gut)
12. If there is time left, cut a small cross-section of the worm below the clitellum
13. Place it on a slide under a dissection scope and draw a what you see (Use a plain white
piece of paper)
14. Label the following parts:
a. Epidermis
d. Gut (intestine)
b. Muscles
e. Coelom
c. Blood vessel
IV.
Data
A. Diagram – see attached
B. Observations
# of segments between mouth and clitellum: _____________
Length of worm from mouth to anus (in cm): _____________
C. Data Table – n/a
D. Graph – n/a
E. Analysis Questions (retype the question, then type the answer below it)
1. What is one thing that you thought was interesting about the external structure of
the earthworm?
2. What is the job of the crop?
3. What is the job of the gizzard?
4. What is one thing that you thought was interesting about the internal structure of
the earthworm?
V.
Conclusion
(see pink sheet for prompts…skip hypothesis prompts as there isn’t one for this lab )
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