Gas Exchange: Fish

Question 1

What are the gills of fish composed of? How does oxygen reach the gills?

Answer 1

• Gill filaments
• Each gill fillament is covered in lamellae.
• This creates a large surface area.
• When fish opens mouth, water rushes in/ over the gills.

Question 2

Why do fish require gas exchange surface?

Answer 2

• Fish = waterproof and have small surface area to volume ratio.

Question 3

What are the adaptations of gills in fish for efficient gas exchange?

Answer 3

• Large surface area to volume ratio: many gill filaments covered in many gill lamellae.
• Short diffusion distance –> capilary network in every lamellae and very thin gill lamellae.
• Maintain concentration gradient –> through countercurrent flow mechanism.

Question 4

How does capilary network in gill lamellae allow for a short diffusion distance for the exchange of gases?

Answer 4

• Capilary network = very close to the water that will flow across gill fillaments/ lamellae.

Question 4

What is the counter-current flow principle?

Answer 4

• Water flows over gills in opposite direction to flow of blood in the capilaries.
• Countercurrent flow ensures that equilibrium isn’t reached.
• Ensures a diffusion gradient is maintained across the ENTIRE length of the gill lamellae.

Question 5

True or False

Counter-current flow principle in fish means that diffusion gradient is maintained across a short length of the gill lamellae.

Answer 5

• False.
• Counter-current flow principle ensures that diffusion gradient is maintained across the ENTIRE length of the gill lamellae.
• Concurrent flow is when diffusion gradient is maintained across short length of gill lamellae.

Question 6

Give the equation to calculate the rate of diffusion, what is this equation known as?

Answer 6

(Rate of) diffusion = surface area x difference in concentration/ length of diffusion pathway.
Fick’s Law