16D (bio)

• Mollusks

  Members of phylum Mollusca in kingdom Animalia, including slugs, oysters, octopuses, clams, cuttlefish, nautiluses, and snails
• Mollusks

  • Have three germ layers, exhibit cephalization and bilateral symmetry, have digestive, circulatory, nervous, and respiratory systems
• Categories of mollusks

  • Bivalves
  • Gastropods
  • Cephalopods
• Bivalves

  • Have two shells, a fleshy muscular foot to help them move
• Gastropods

  • Include slugs and snails, have a foot found below the visceral mass
• Cephalopods


  • Have feet divided into sucker-bearing arms used to catch food, can change color for camouflage and communication
• Mollusk anatomy

  1. Have a mouth and radula (organ with tiny teeth) for scraping and pulling in food

  2. Some have a nervous system with ganglia

  3. Underwater mollusks breathe using gills

  4. Cephalopods have closed circulatory systems, bivalves and gastropods have open circulatory systems

  5. Mollusks circulate water through siphons, can jet water out to move quickly
• Mollusks are the second largest phylum in kingdom Animalia
• Mollusk reproduction

  • Most mollusks reproduce sexually
  • Simpler mollusks reproduce through external fertilization, with some species such as snails being hermaphrodites
  • More complex mollusks such as cephalopods mate and reproduce through internal fertilization
• Mollusk reproduction

  1. Fertilization produces eggs

  2. Eggs hatch to release larvae

  3. For water-dwelling mollusks, larvae float as plankton

  4. For simpler mollusks, larvae are trochopores similar to the larvae of earthworms and go through metamorphosis

  5. In cephalopods, the young that hatch from eggs are just smaller versions of their adult form
• Mollusk function in the environment

  • Some mollusks live on land, but most are aquatic
  • Mollusks can be carnivores, herbivores, and scavengers
  • Mollusks play a role in a variety of ecosystems, such as the coral reef community
• Mollusk function in the environment

  • Mollusks eat algae, detritus, and even each other, with some mollusks like sea snails preying on sea cucumbers
• People use mollusks to enrich and improve their lives
• Mollusk uses

  • Some mollusks are edible, such as the abalone
  • Scientists are studying the regenerative power of mollusks to help create therapies and medications that can help people with specific medical problems