Download Earthworm dissection

Earthworm dissection:
A. External anatomy:
1. Measure the length of your worm in centimeters: ______________ cm.
2.. Count the number of segments of your earthworm.
_________________segments
Compare this number to someone else’s worm.
number of segments on another worm __________________
3. Contrast (tell me the difference) the anterior end from the posterior end.
a. The earthworm’s back is (lighter, darker) than its belly. What
advantage to survival would this color difference provide the worm?
b. The segments on the front end of the worm are (smaller, larger) than
those toward the rear end.
c. The size of the body is (larger, smaller) toward the front end of the
earthworm. Speculate (give me your idea) why the front end is this way?
4. Run your finger along the sides of the earthworm toward the anterior
end and then the posterior end.
a. What do you feel sticking out the sides?
b. If a bird was pulling on the worm to eat it, how could this help protect
the worm?
5. Go to Mrs. Buscher’s links on her webpage...Bio 134 dissections...open the
earthworm dissection images link.
a. Look at slide 1 (dorsal side) and locate the clitellum. This area
secretes mucus to hold the worms together during reproduction.
B. Internal anatomy: Highlight each instruction as you perform the task.
1. To cut your worm, place the worm on its ventral (belly) side.
2. Insert your scissors in to the mouth and snip with your scissors, segment
by segment, from anterior (head) to posterior end along the dorsal side. DO
NOT CUT PAST THE CLITELLUM.
3. Your worm will not open up until you carefully break the septa (thin
walls) holding the skin to worm’s body. With your scissors, run the sharp point
down the insides of the skin to sever the septa. Then pin your earthworm down
to the pan.
4.Refer to the list of organs and structures you are going to locate. Make
certain each person in your group can identify each structure. There will be a
short picture identification test tomorrow. You will work your way from the
intestine to the mouth.
DIGESTIVE SYSTEM
* intestine -finishes digestion & food diffuses into blood
* gizzard - grinds food into pieces (when you push on this it bounces back)
* crop -moistens food
* esophagus (-carries food to crop
* mouth & pharynx -tonguelike structure that pulls food into mouth
REPRODUCTIVE SYSTEM
* seminal vesicles– Stores the worm’s sperm
* seminal receptacles – Stores the sperm from the OTHER worm it is
mating with
CIRCULATORY SYSTEM
* aortic arches & dorsal blood vessel - pumps & carries blood
* ventral blood vessel- on the belly side but not shown in images
NERVOUS SYSTEM
* ventral nerve cord and brain- receives and carries messages
COLOR CODE AND LABEL
*EACH STRUCTURE OF THE EARTHWORM AS YOU DISSECT
(anus, clitellum, gizzard, crop, intestine, mouth, pharynx, hearts, esophagus,
brain, ventral nerve cord, ventral blood vessel, dorsal blood vessel)