Worms

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Worms
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Flatworms

• 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

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Flatworm Reproduction

• Asexual
• Stretch are break apart
• Each half becomes new animal
• Sexual
• Hermaphrodites
• Both transfer sperm to one another
• Web link

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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
• Flukes
• Internal or external parasites
• Contain protective layer to prevent from being
  digested
• Ex Schistosomiasis

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One Final Look
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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

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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

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• Ascaris
• 1) Worms in intestines
• 2) Eggs pass through feces
• 3) Egg begins to develop
• 4) Larvae ingested
• 5) Larvae hatch in intestines
• 6) Larvae bore into bloodstream (enter lungs and
  throat)
• 7) Coughed up and reswallowed into intestones

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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

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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

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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