6.3 - Gas Exchange In Fish

Question 1

Where does gas exchange occur in a fish?

Answer 1

The gills

Question 2

What are gills made of and how are they supported?

Answer 2

Made of bone or cartilage and supported by the gill bar/arch

Question 3

What is the space between the gill bar called?

Answer 3

Gill slit

Question 4

How many rows of filament are there?

Answer 4

2

Question 5

What are lamellae?

Answer 5

Folds on the filament

Question 6

Where does gas exchange occur in a fish?

Answer 6

The lamellae

Question 7

How big is the distance between the water and the blood cells in the lamellae?
Why is this good?

Answer 7

• 5 micrometers
• Short diffusion distance

Question 8

What prevents the lamellae from collapsing?
How large is the gap between two lamellae?

Answer 8

• the water in between them
• 50 micrometers

Question 9

What are the two ways fish can ventilate?

Answer 9

Passive ventilation and active ventilation

Question 10

Passive ventilation (2 ways)

Answer 10

• Fish swim forward with their mouth open
• Fish point they mouth upstream

Question 11

What are the 5 stages of active ventilation in a fish?

Answer 11

1) Mouth opens and operculum closes
2) Buccal floor lowers so the buccal cavity volume increases. As the volume increases, the pressure decreases and the water flows in (like a suction pump)
3) Mouth closes
4) Buccal floor raises so the pressure increases
5) Operculum opens so the water is pushed out through the gills

Question 12

Explain counter current flow.

Answer 12

• water and blood flow in opposite directions across the lamellae
• this maintains a concentration gradient
• therefore diffusion can occur across the whole length of the lamellae

Question 13

Explain parallel flow

Answer 13

• Blood and oxygen flow in the same direction
• Concentration gradient is harder to maintain