Mollusks

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Mollusks

• Bivalves
• Gastropods
• Cephalopods

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Characteristics of Mollusks

• Invertebrates with a soft, unsegmented body often
  protected by a shell.
• They have a thin layer called the Mantel that
  covers the internal organs and has a foot.
• Bilateral symmetry
• Digestive system with two openings

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Characteristics continued

• Open Circulatory System, blood is not always in a
  vessel
• Gills allow mollusks to get oxygen from the water

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Gastropod- Snails and Slugs

• The largest group of mollusks
• They can live in almost any environment on Earth
• They have a single external shell or none at all
• Some are herbivores (plant eaters) others are
  scavengers (eat decaying material) and others are
  carnivores (meat eaters)

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Gastropods continued

• Radula- flexible ribbon of tiny teeth to get food
• Move by creeping on foot along with the mucus
  they produce to help slide. Dont move very fast
  

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Bivalves- oysters, clams, scallops

• They have two shells that are held together by
  hinges and strong muscles
• Filter feeders to get food. Food sticks to the
  gills and cilia helps move the food to the mouth.
  Omnivores mostly eating plants and animals.
• Dont move easily, they can attach themselves to
  other moving things

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Bivalves continued

• For protection they can create a smooth coat over
  sand or other things that cause irritation.

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Cephalopods- Octopus and Squid

• An ocean dwelling mollusk whose foot is adapted
  to form tentacles around the mouth
• Closed Circulatory System
• Carnivores, the suckers let the animal taste and
  touch
• Large eyes and excellent vision
• Complex nervous system
• Large brain and can learn things

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Cephalopod continued

• Swim by jet propulsion
• They use ink for protection