Fish and insects

• Why is water a challenging medium for gas exchange in fish?

  Water has a lower concentration of oxygen than air
• What are additional reasons water makes gas exchange difficult for fish?

  • Water is much denser than air
  • Fish can be very active, requiring high oxygen supply
• Why can’t gases diffuse through fish skin?

  Fish skin is impermeable to gases
• Why wouldn’t a mammalian-style respiratory system work for fish?

  It would lack sufficient surface area for gas exchange in water
• What structure do fish use for efficient gas exchange instead of lungs?

  Fish use gills
• What are key adaptations of gills for gas exchange?

  • Large surface area for more diffusion
  • Permeable membranes for gases to diffuse
• What are additional adaptations of gills for gas exchange?

  • Thin (flattened cells) for short diffusion distance
  • Good blood supply to maintain a steep concentration gradient
• How do gills in fish resemble mammalian lungs?

  • Both have large surface area
  • Both have thin barriers for short diffusion distances
• What protects the gills of bony fish?

  The operculum protects the gills
• What is the role of the operculum besides protection?

  It ensures water flows in the right direction over the gills
• What supports the gills of bony fish?

  Bony gill arches support the gills
• What is the structure of the gill filaments?

  Each gill has two rows of primary lamellae
• What are gill plates, and what is their role?

  Gill plates cover the gill filaments and increase surface area
• Why are gills bright red in color?

  They are rich in blood supply
• Why do gills have many filaments and gill plates?

  To create a very large surface area for gas exchange