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Earthworm Dissection Worksheet
(1) The earthworm belongs to the phylum Annelida and shows bilateral symmetry. The small projection that
sticks out over the mouth is called the prostomium. The enlarged section around a short length of the body is
called the clitellum. What is its purpose? Secretes a “cocoon” to protect the eggs
(2) When you pass your fingers over the ventral and lateral sides of the earthworm you feel the setae. There
are 4 pairs of these per segment and are used for locomotion.
(3) Below is a cross-section of an earthworm. Label the setae, body wall, coelom, intestinal wall, intestinal
opening, dorsal blood vessel, ventral blood vessel, ventral nerve cord, and nephridia.
coelom
(4) The earthworm has a one-way digestive system. What does this mean? Food comes in one end (mouth)
and waste goes out the other (anus)
(5) What are the benefits of having a one-way digestive system instead of a two-way? Allows for a tube
with specialized areas for separate functions (like an assembly line in a factory)
(6) Place the following structures of the earthworm’s digestive system in the
proper order for food passage:
anus, gizzard, pharynx, esophagus, mouth, crop, intestine
mouth  pharynx  esophagus  crop  gizzard  intestine  anus
(7) Draw the digestive tract and label it. (see picture to right)
(8) What type of circulatory system does an earthworm have? Explain.
Closed (blood is carried within vessels)
(9) What pumps the blood and where are they found? 5 pairs of aortic arches – enlarged pulsating blood
vessels (not real hearts because they do not have chambers) – found around esophagus
(10) Worms are hermaphrodites – explain. Have both male and female reproductive organs. Can not selffertilize (must exchange sperm)
11) How does an annelid rid itself of cellular wastes? Nephridia (one pair per segment)
12) How does the earthworm’s main nerve cord differ from yours? Earthworm  ventral, Human  dorsal
13) How does an earthworm get oxygen required for cellular respiration? Absorbs oxygen through the
process of DIFFUSION into their moist skin of their circulatory system (capillaries)