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. (see Part II)
▪ 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 posterior region 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.
Lab_Science7
Name:__________________________________
Date:________________________ Period:_____
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: http://www.flushing.k12.mi.us/srhigh/tippettl/biology/lum/.
8. The worm’s digestive system has the following parts. Locate these parts & write the function.
▪ Mouth: tiny opening at anterior end through which food enters
▪ Pharynx: “throat” smooth part behind the mouth
▪ Esophagus: main food tube connecting pharynx to crop
▪ Crop: (1st stomach) temporary holding tank / food storage
▪ Gizzard: (2nd stomach) grinder
▪ Intestine: longest tube absorbs nutrients (food) and water
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): (5 of them) pump blood
▪ Dorsal Blood Vessel: main 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 mucus
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: site of mating (smooth band where sperm meets egg)
▪ Seminal Vesicles: produce sperm (large white organs)
▪ Seminal Receptacles: store sperm (smaller white organs)
11. Earthworms have a simple nervous system which allows worm to sense its surroundings. 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: senses stimuli and sends messages to brain
(small white cord under intestine)
Lab_Science7
Name:__________________________________
Date:________________________ Period:_____
Part IV – Labeling Diagrams
12. Label the following diagram with the letter appearing in front of the word.
a. Mouth
2. __ _
b. Pharynx
c. Esophagus
1. __ _
d. Crop
e. Gizzard
f. Intestine
g. Aortic Arches (Hearts)
h. Dorsal Blood Vessel
i. Ventral Blood Vessel
j. Clitellum
k. Seminal
Vesicles
DAY
2 - LAB
14. __ __
l. Seminal Receptacles
m. Ventral Nerve Cord
n. Brain
n
c
3. __ __
a
g
h
7. __ __
4. __ __
5 __
f
k
6. __ __
b
l
13. ___ _
d
12. __ __
i
e
11__ __
10. __
j
8. __ __
9. __ __
m__
Lab_Science7