#7 Earthworms
Holy Cross School
7th Grade Biology
Wong
External Anatomy
•
•
Anterior -the front end of a worm is the thicker and
fleshier part of the body.
Posterior- the thinner back end
http://www.pgjr.alpine.k12.ut.us/science/whitaker/Animal_Kingdom/Earthworm/Earthworm.html
External Anatomy continued
• Ventral side- the bottom side of the worm. It is usually
lighter color than the top in living worms.
• Dorsal side- the top side of the worm.
http://www.pgjr.alpine.k12.ut.us/science/whitaker/Animal_Kingdom/Earthworm/Earthworm.html
External Anatomy continued
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Clitellm is about 1/3 back from the anterior of the
worm. It is thick and cylindrical. (1)
Setae are bristles on the ventral side of the worm.
These hair-like structures help the worm move and
sense its environment.
http://biog-101-104.bio.cornell.edu/BIOG101_104/tutorials/animals/worm_stuff/worm_dorsal.html
External Anatomy continued

Segments are little raised sections that look like
rings around the earthworm’s body. The grooves
between each segment are called septum.
http://www.pgjr.alpine.k12.ut.us/science/whitaker/Animal_Kingdom/Earthworm/Earthworm.html
Next Up...Internal Anatomy…
Earthworms are invertebrates- they have
no backbone.
Get ready now….
We are going to look inside the
earthworm…
Circulatory System

Dorsal blood vessel
 Is the main vessel of the system and is on top of the
digestive track.
http://www.flushing.k12.mi.us/srhigh/tippettl/biology/lum/
Circulatory System


Ventral blood vessel
 Is on the opposite side of the dorsal vessel, below the
digestive track.
The two vessels cross over at the digestive tract.
Earthworms have five pairs of “hearts” the pump and
exchange blood.
http://www.flushing.k12.mi.us/srhig
h/tippettl/biology/lum/
Digestive System
Digestive System
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Earthworms are not picky eaters. They will eat
anything from decay plants to animals.
Mouth is located at the anterior end.
Pharynx is a muscle that provides worms with a
suction to pull food in its mouth.
http://www.flushing.k12.mi.us/srhig
h/tippettl/biology/lum/
Digestive System continued…
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From there the food travels down the tube like
structure called an esophagus. People have an
esophagus as well.
The food is temporary stored in a part of the
body called the crop.
http://www.flushing.k12.mi.us/srhigh/tippettl/biology/lum/
Digestive System continued…
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The food is move from the crop into the gizzard. This is
where food is ground up by strong muscle contractions.
Food is next moved in the intestine for absorption.
Material that is not absorbed is pass out through the
anus on the anterior end.
http://www.flushing.k12.mi.us/srhig
h/tippettl/biology/lum/
Reproductive System
• Earthworms are hermaphrodites. This means they
male and female reproductive organs. Even though
they have both male and female organs, they
reproduce through cross-fertilization.
http://www.flushing.k12.mi.us/srhig
h/tippettl/biology/lum/
Nervous System

Ventral nerve cord is the major component of the
nervous system. It runs the entire length of the
worm on the ventral side. (2)
http://biog-101-104.bio.cornell.edu/BIOG101_104/tutorials/animals/worm_stuff/worm_dorsal.html
Nervous System continued…
 The brain is located at the anterior end of the worm
and is connected to the ventral nerve cord. (9)
http://biog-101-104.bio.cornell.edu/BIOG101_104/tutorials/animals/worm_stuff/worm_dorsal.html