Transcript Earthworm Dissection

Earthworm Dissection
Students will use the following tools
for the earthworm dissection
•
•
•
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Scalpel
Probes
Dissecting Pins
Rubber Padded Dissecting Tray
Scalpel
Probe
Dissecting Pins
Dissecting Pan
Before you start dissecting, find the
following:
• Mouth
• Setae – the bristles used for locomotion.
They are located by rubbing your fingers
along the earthworm’s body. They are
often times easier to feel than to see.
• Sperm Duct
• Clittelum
Sperm
Duct
Sperm Groove
sperm moves
along here from
sperm duct to
another worm
Oviduct
tube through which
eggs pass
Clittelum makes mucus
Setae – bristle like
structures that help
the worm move
Mouth
Pin your worm at the tip of
the mouth and at its
midpoint.
Continue your cut to the
mouth
Start your incision 2 cm behind the
clittelum.
Make sure not to cut too deeply.
Begin to separate
the skin using pins
Pin the skin back as
you go along the
cut. Angle your pins
outward so that are
out of the way.
As you pin the
skin back, take
your probe and
break the
partitions
between the
segments.
These are called
Septum.
A comparison of systems…
Circulatory System
“heart”
“veins”
carries blood
to the “heart”
“arteries”
carries blood
away from
the “heart”
• Aortic Arches surround the
esophagus and
function in pumping
the blood throughout
the body
Aortic Arches – Earthworms
have 5 pair of these simple
hearts.
Aortic Arch
• Ventral Blood
Vessel- carries blood
from the aortic arches
to the rest of the body
• Dorsal Blood
Vessel- Returns
blood to the aortic
arches and has
valves to prevent
backflow
Digestive System
• Food goes from the:
Mouth
Pharynx
Esophagus
Crop
Gizzard
Intestine
Anus
• Mouth- opening at
the end allowing the
intake of food
consisting of particles
of both living and
dead substances
Mouth
• Pharynx- moves food
from the mouth to the
esophagus
Pharynx
• Esophagus- Carries
food between the
pharynx and the crop
• Crop – Stores food
Crop
• Gizzard – grinds food
Gizzard
• Intestine – Digests
food
Intestine
Dorsal Blood
Vessel
• Anus – where
excrement (poop)
comes out
Nervous System
• Ganglion- group of
nerves. In the
earthworm, there is a
pair of ganglia in each
segment and a
cerebral ganglia acts
like a brain
Brain
Nerve Cord
and Brain
• Ventral Nerve Cordconnects the ganglia
in each segment of its
body with the cerebral
ganglia. It coordinates
movement
Ventral Nerve
Cord
Ventral Nerve
Cord
Reproductive System
• Earthworms are hermaphrodites which
means they have both male and female
body parts
Seminal Vesicles- store sperm produced by the earthworm
Seminal Receptacles
paired organs that store sperm received from
another worm during copulation