Fish

• cartilaginous fishes


  fish with skeletons made of cartilage
• jawless fish


  parasitic and lack many vertebrate features
• bony fishes


  spine and soft rays support membranous fins. 95% of fishes
• fins


  used by fish to steer, maintain stability, and move
• scales


  for protection
• mucus


  a layer found in bony fishes, reduces drag and protection from parasites
• countershading


  fish have darker color on upper body and lighter on lower for camouflage
• lateral line


  dark line composed of sensory organs
• fish have closed circulatory system
• fish have 2 chambered heart

  • atrium
  • ventricle
• swim bladder


  fills with air to keep fish afloat