Transcript Worms - Cloudfront.net

Worms
Flatworms
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Bilateral symmetry
No coelum
Has organs & systems
3 body layers
– Ectoderm
– Mesoderm
– Endoderm
• Gasses pass in/out by diffusion
• Anterior end w/ mouth
• Primitive brain
Flatworm Reproduction
• Asexual
– Stretch or break apart
– Each half becomes new
animal
• Sexual
– Hermaphrodites
– Both transfer sperm to one
another
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Flatworm Parasites
• Tapeworms
– Larvae enter through
undercooked meat
– Hooks attach to inner
walls of intestines
– Food absorbed through
skin
– Grow up to 12 meters
One Final Look
Roundworms
• Cylindrical bodies w/ mouth and anus
• Separate male/female
– Sexual reproduction
• 1st to have body cavity (coelum)
– Movement of fluid circulates gas & nutrients
• Most small in size (few mm)
• Most free-living
Roundworm Parasites
• Ascaris
– Infects pigs, horses, humans
– Knots of worms can block intestines
(cause death)
– Larvae cause respiratory illness
– Females: lay 200,000 eggs/day
• Trichinella
– Eat undercooked pork
– Larvae burrow into intestines &
mature
– New larvae pass into blood & form
cysts in muscles
Segmented Worms
• Have coelum
• 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
Segmented Worm Reproduction
• Hermaphroditic
• Ventral surfaces press together
– Mucus holds worms together
• Sperm released into the mucus & stored in a
pouch
• Worms develop inside pouch
Segmented Leeches
• Live in calm, freshwater
• Sucker attached to host
or prey
• Release anaesthetic to
hide presence
• Can eat up to 10x own
weight
• Used to help restore
blood flow in limb
reattachment