Name:______Date:______Period:_____

Lab: Earthworm Dissection

DAY 1 – PRE-LAB

Part I – Terminology

1. There are several terms you should be aware of before beginning your dissection. These words will

help you orient yourself when you dissect your worm.

▪Anterior - ______

▪Posterior - ______

▪Dorsal - ______

▪Ventral - ______

Part II – External Anatomy

2. The top of the earthworm is the dorsal side. This is the darker side of the worm. Find the dorsal

side of your worm and show your teacher.

3. The bottom of the earthworm is the ventral side. This is the lighter side of the worm. Find the

ventral side of your worm and show your teacher.

4. The anterior region of the earthworm is the head region. There is a mouth at the head region. Find

the mouth of your worm and show your teacher.

5. The posteriorregion of the earthworm is the tail region. There is an anus at the tail region. Find

the anus of your worm and show your teacher.

6. Note the swelling of the earthworm near its anterior side. This is the clitellum. Find the clitellum

of your worm and show your teacher.

7. Each segment of a worm has small pairs of bristles called setae which help it move. Run your

fingers up and down the ventral side of the worm to fell the bristles.

Part III – Virtual Dissection

You will be identifying several structures when you dissect your worm. To help you feel comfortable identifying those structures we will look at images of an earthworm dissection at the following Website:

8. The worm’s digestive system has the following parts. Locate these parts & write the function.

▪Mouth: ______

▪Pharynx: ______

▪Esophagus: ______

▪Crop: ______

▪Gizzard: ______

▪Intestine: ______

9. Earthworm’s have a closed circulatory system which means all body fluids are contained within

small tubes. An earthworm’s circulatory system has the following parts. Locate these parts on the

Website & write the function.

▪Aortic Arches (Hearts): ______

▪Dorsal Blood Vessel: ______

10. Earthworms have both male and female reproductive organs, but does not fertilize itself.

Earthworms reproduce sexually by lining up and exchanging sperm. The clitellum secretes muscus

that picks up the egg and sperm cell forming a cocoon. The cocoon is dropped into the soil where

a new earthworm develops. NOTE: The ovaries and testes are there but too small to see. An

earthworm’s reproductive system has the following parts. Locate these parts & write the function.

▪Clitellum: ______

▪Seminal Vesicles (produce sperm): ______

▪Seminal Receptacles: ______

11. Earthworms have a simple nervous system. The brain is very small and usually hard to see. A

nerve cord is located on the ventral side. Locate the nerve cord & write the function.

▪Ventral Nerve Cord: ______

Part IV – Labeling Diagrams

12. Label the following diagram with the letter appearing in front of the word.

DAY 2 - LAB

Part IV – Dissection

1. Stretch your worm out with the dorsal side up in a dissecting pan.

2. Pin the earthworm to the pan using one pin at eachend of the worm.

3. Locate the clitellum and insert the tip of the scissors just 3 cm from the clitellum.

4. Carefully cut all the way up to the head. Try to keep the scissors pointed up and ONLY CUT

THROUGH THE SKIN!

5. Spread the skin of the worm out and pin the skin to the dissection pan. Slant

the pins at an angle.

6. Once you have completely opened your earthworm, identify the following internal organs by using

your earthworm from the pre-lab. Once you are ready, call your teacher over for grading.

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Name:______Date:______Period:_____

▪_____ Mouth

▪_____ Pharynx

▪_____ Esophagus

▪_____ Crop

▪_____ Gizzard

▪_____ Intestine

▪_____ Hearts

▪_____ Dorsal blood vessel

▪_____ Clitellum

▪_____ Seminal vesicles

▪_____ Seminal receptacles

▪_____ Ventral Nerve Cord

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Name:______Date:______Period:_____

7. Analysis (complete sentences):

a. Why would the earthworm have bristles (setae) on the outside of its body? (2 pts)

b. What types of organ systems does an earthworm have? Name the systems and describe the

function of each. (HINT: One example of an organ system is the Nervous System since the brain

and nerve cord work together to help a worm feel and sense its surroundings.) (8 pts)

c. Discuss two parts of the external (outside) anatomy that was interesting to you. Make sure to state

the part and describe it fully. (4 pts)

d. Discuss two parts of the internal (inside) anatomy that was interesting to you. Make sure to state

the part and describe it fully. (4pts)

Scoring Guidelines:

Virtual Dissection - function of each earthworm part is correct _____/ 2 pts

All parts of earthworm correctly identified during dissection _____/ 12 pts

Analysis questions answered correctly in complete sentences _____/ 18 pts

TOTAL: _____/32 pts

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