gas exchange in fish

• Why can't fish simply diffuse oxygen across their surface?

  They have a small surface area to volume ratio
• What is the gas exchange surface in fish?

  The gills
• How much less oxygen does water contain compared to air?

  30 times less oxygen
• What are the three key features of every gas exchange surface?

  Large surface area, short diffusion distance, concentration gradient
• What adaptations do fish gills have for gas exchange?

  • Large surface area from gill filaments
  • Short diffusion distance due to thin lamellae
  • Counter current flow to maintain concentration gradient
• How is the rate of diffusion calculated in gas exchange?

  Using Fick's law
• What does Fick's law state about diffusion?

  Diffusion is proportional to surface area and concentration difference
• How many layers of gills do fish have on each side of their head?

  Four layers
• What are the long parts sticking out of the gills called?

  Gill filaments
• How are gill lamellae positioned in relation to gill filaments?

  At right angles to the gill filaments
• What is the purpose of the capillary network inside gill lamellae?

  To provide a short diffusion distance
• What is the counter current flow in fish gills?

  Water flows opposite to blood in capillaries
• Why is counter current flow advantageous for fish?

  It prevents equilibrium, maintaining diffusion
• What happens to the concentration of oxygen in water as it flows over the gills?

  It decreases from 100% to near 0%
• What is the result of concurrent flow in gas exchange?

  Equilibrium is reached, limiting diffusion
• What is the key advantage of counter current flow over concurrent flow?

  Maintains diffusion gradient across entire lamellae
• What are the three features of gas exchange in fish gills?

  1. Large surface area from stacked gill filaments
  2. Short diffusion distance due to thin lamellae
  3. Counter current flow to maintain concentration gradient
• What should be noted about the diffusion gradient in concurrent flow?

  It is not maintained across the entire length
• What is the significance of the term "entire" in gas exchange?

  Indicates diffusion occurs along the full length
• What is the final summary of gas exchange in fish?

  Surface area, short distance, maintained gradient
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