worms

• worm attributes

  • 3 germ layers
  • few to no appendages
  • bilateral symmetry
  • soft and long bodies
• roundworms

  • nematodes
  • tiny and round
  • found on land, water, and inside bodies
  • some are parasitic
• segmented worms

  • annelid
  • bumpy body called a segmented body plan
  • 3 germ layers
• flatworms

  • flat bodies
  • mostly parasites
  • planarians are free-living in water
• all worms exhibit bilateral symmetry
• segmented and roundworms have cephalization
• free-living worms are more complex than parasitic worms
• worms perform extracellular digestion
• extracellular digestion is the breakdown of food in the mouth and stomach before it gets to the cells
• ganglia two bundles of nerve cells in the brain and spinal cord
• tegument living cells on outer layer of flatworm
• cuticle is the nonliving layer in roundworms and segmented worms
• segmented worms have closed circulatory system
• closed circulatory system

  transports nutrients from food through vessels
• al worms possess a mesoderm in their embryonic form
• flatworms and roundworms have no body cavity, therefore lacking a circulatory system