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Worms
Flatworms
ectoderm
mesoderm
• Bilateral symmetry
• Have organs &
systems
– Primitive brain
– Pharynx: mouth tube
• 3 body layers
– Ectoderm
– Mesoderm
– Endoderm
Able to
“regenerate”
endoderm
http://www.youtube.com/wat
ch?v=0L_mJoG4nts
• Gasses pass in/out
by diffusion
• Reproduction:
– Asexual: stretch and
break apart
– Sexual: “fencing”
Flatworms
• Bilateral symmetry
• Have organs &
systems
– Primitive brain
– Pharynx: mouth tube
• 3 body layers
– Ectoderm
– Mesoderm
– Endoderm
• Gasses pass in/out
by diffusion
• Reproduction:
– Asexual: stretch and
break apart
– Sexual: “fencing”
Flatworm Parasites
Larvae not killed in cooking process
• Tapeworms
– Larvae enter
through
undercooked meat
– Larvae grow
– Scolex (head with
hooks) attach to
wall of intestines
– Food absorbed
through skin
– Grow up to 12
meters
– Eggs released in
poop
– Contaminated poop
water consumed
Roundworms (Nematodes)
• Protostomes; Bilateral
symmetry
• Small in size (few mm)
• Nerves control
longitudinal muscles
• What’s new?
– Mouth and anus
– Pseudocoelum: body
cavity to aid with
circulation &
digestion
• Separate male/female
• Some free-living; Many
parasites
Roundworm Parasites
• Hookworms
– Larvae enter through
bare feet walking in
contaminated water
– Migrate into lungs
– Migrate into
esophagus and
swallowed into
stomach
– Larvae mature inside
intestines
– Mating occurs inside
host
– Eggs exit the host in
poop
https://www.youtube.com/watc
h?v=DxL2qHBetvI
Egg
• What’s new?
– Coelum: cavity to aid
with circulation &
digestions
– Completely surrounded
by muscle
• Several organ systems
– Complex digestive
system
– Circulatory sys: 2 blood
vessels
– Nervous sys: Primitive
brain and nerve cord
– Muscular sys: Circular &
longitudinal muscles
• Gas exchange through skin
• Eat organic waste
Segmented Worms
(Annelids)
Longitudinal
muscles
Circular muscles
Segmented Worm Reproduction
. .. . .
.M
F
F
M.
• Hermaphroditic
• Ventral surfaces press together
– Mucus holds worms together
– Sperm transferred to each
– Sperm pouch forms
– Sperm & eggs enter pouch as worm backs out
– Baby worms develop inside pouch
Segmented Leeches
• Live in calm, freshwater
• Suckers attach to host
• Release anaesthetic to
hide presence
• Can eat up to 10x own
weight
Segmented Leeches
• Live in calm, freshwater
• Suckers attach to host
• Release anaesthetic to
hide presence
• Can eat up to 10x own
weight
• Medicinal use:
– Help restore blood flow when
body part is severed and
reattached
Ouch!
blood
blood
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