Phylum Platyhelminthes

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Phylum Platyhelminthes
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Characteristics

• Flatworms
• Soft body
• Flattened
• Have tissue
• Have internal organ systems
• Bilateral symmetry
• Acoelomates
• Many are parasites

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Body Plan

• Long narrow body
• Only a few millimeters thick
• Has muscles!
• No skeleton

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Feeding

• Can be carnivores, scavengers, or parasites
• gastrovascular cavity with one opening- food and
  waste pass through this.
• Pharynx-muscular tube near mouth
• Comes out and pumps food in

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Respiration, Circulation, Excretion

• Takes in oxygen and nutrients through thin body
  and lets out CO2 diffusion
• no respiratory organs
• No heart, blood vessels or blood
• Flame cells- specialized to filter and remove
  access water

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Response

• Simplest organisms with a brain
• Ganglia in head (group of nerve cells)
• Two simple nerve cords and two brains are small
  bundles of nerves
• Some have eyespots
• Can detect canges in the amount of light in their
  environment

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Reproduction

• Asexual reproduction
• Fragmentation (planarians)
• Sexual Reproduction
• Monoecious
• Pair up and deliver sperm to each other
• Lay eggs that hatch in a few weeks

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Habitat

• Free-living
• Ocean
• Freshwater
• Moist soil
• Parasites
• On or in host organism

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Classes

• Flatworms
• Class Trematoda Tapeworms
• Class Cestoda Flukes
• Class Turbellaria
• Planarians