mollusks

• mollusks attributes

  • 3 germ layers
  • exhibits cephalization
  • bilateral symmetry
  • have all body systems
  • mostly aquatic
• mollusks

  bivalves, gastropods, cephalopods
• bivalves

  they have a fleshy mantle that protect their organs, a shell to protect its mantle, and a fleshy foot (e.g. oysters, clams, scallops)
• gastropods

  • some live on land
  • have a foot below it's visceral mass
• visceral mass contains the heart and digestive system of a slug
• cephalopods

  • have feet divided into sucker-bearing arms for capturing prey
  • have chromatophores for camouflage
  • e.g. cuttle fish and octopus
• chromatophores


  pigment bearing cells
• some mollusks have shells
• radula: (in a mollusk) a structure of tiny teeth used for scraping food particles off a surface and drawing them into the mouth.
• mollusks have ganglia
• ganglia

  clusters of neurons that connect to other neurons and form a network
• gills


  present in aquatic mollusks for respiration
• siphons


  2 tubes, one for bringing in water, one for bringing it out
• simpler mollusks perform external fertilization
• complex mollusks perform internal fertilization e.g. cephalopods
• some mollusks, such as snails, are hermaphrodites
• most mollusks perform sexual reproduction
• mollusks eggs hatch as larvae
• for water-dwelling mollusks, larvae float as planktons
• trochophores: have a single pair of wings, but no wings in the adult stage
• simpler mollusks

  • trochophores, like earthworm larvae
  • they mature through metamorphosis
• cephalopods


  after hatching, they are just smaller version of their parents