Segmented Worms
Annelids
Tube shaped worms with rings
New Words
• Setae- bristle-like structures
• Crop- a sac used for food storage
• Gizzard- a muscle that grinds up bits of soil
and organic matter
• Anterior- front end of an organism
• Posterior –back end of an organism
• Hermaphrodites- organisms that produce
sperm & eggs in the same body
Segmented Worms
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Use setae to hold onto soil and move
Have bilateral symmetry
Body cavity that holds organs
Two body openings (mouth & anus)
Annelids are found in freshwater, saltwater &
moist soil
Earthworm Body Systems
• Have a definite anterior- front end
• Have a definite posterior- back end
• Each body segment (except the first and last)
have a pair of setae & 2 sets of muscles
Earthworms burrow through soil
• They take soil into their mouth
They get energy from soil & other
organic matter found in the soil
• The soil moves to the crop and into the gizzard to
be ground, broken down, and the nutrients
absorbed my the blood
Waste leave the worm
through the anus
Clitellum
A thick ring structure used in reproduction
When earthworms take in soil, they
provide spaces for air and water to
flow
through it and mix the soil
Their wastes pile up a the openings to
their burrows
• We call these wastes “castings”
• The castings help fertilize the soil
Vermicompost
We call these casting VERMICOMPOST
• They are used as an organic fertilizer in
gardens
Earthworms have a
closed circulatory system
Two blood vessels run from the top to
the bottom of their bodies
• They have a heartlike structure called “aortic
arches” which pump blood to the body
Oxygen and carbon dioxide are
exchanged through their skin
• They DO NOT have gills or lungs!
• You can suffocate an earthworm by touching it
with dry hands or by wiping off their mucous
layer
• However – they cannot survive submerged in
puddles of water either
• It is a delicate balance
Earthworms have a small brain in their
front segment of their body
• Nerves in each segment form a main nerve
cord that connects to the brain
Earthworms respond
• To light
• Temperature
• moisture
Earthworms are Hermaphrodites
• They have body male and female reproductive
structures in one body
• One individual CANNOT fertilize its own eggs
• It must receive sperm from another
earthworm in order to reproduce
Earthworms mating
Why would earthworms be
healthy to have in a garden or compost
pile?
Are you ready to dissect?
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