Gas Exchange In Fish

Question 1

What are the 3 reasons fish cannot just rely on diffusion?

Answer 1

-have a waterproof coating
-water is denser than air
-fish have a small surface area to volume ratio.

Question 2

What is the hill covering called?

Answer 2

The operculum

Question 3

How do fish ventillate?

Answer 3

-Swimming continuously or opening and closing their mouths.

Question 4

What is the parallel flow method?

Answer 4

Water and blood flow in the same direction so a diffusion gradient is maintained for only half of the distance across the gill lamellae so only50% of the oxygen from the water diffuses into the blood as equilibrium is reached halfway across the lamellae.

Question 5

What is the counter current flow?

Answer 5

Blood and water flow in opposite directions so a diffusion gradient is maintained across the whole distance of the gill lamellae so all oxygen can diffuse into the blood.

Question 6

What ways are fish adapted for efficient diffusion?

Answer 6

-Have pressure changes in mouth to ventilate gills so it maintains a high diffusion gradient.
-Have many filaments and lamellae for a large surface area.
-Have a large number of capillaries so oxygen is removed from the gills quickly maintaining a high diffusion gradient.
-Thin walls on lamellae and capillaries for short diffusion pathway.

Question 7

Why can young/small fish get enough oxygen without having gills?

Answer 7

-They will have a very small surface area to volume ratio so they can rely on diffusion alone as they have a short diffusion pathway.