Fish

Question 1

Describe the structure of gills

Answer 1

There a 4 pairs of gill (branchial) archs. They are made up of gill filaments. The gill filaments are stacked to form gill lamellae and gill lamellae is coved by a muscular flap called the operculum

Question 2

Purpose of gill lamellae

Answer 2

It increases the sa of the gills

Question 3

Describe the movement of water through gills

Answer 3

• fish open there mouth and lower the buccal cavity
• this increases the volume and decrase pressure in the mouth compared to the outside this causes water to enter
• fish closes it mouth and the floor raises
• this decreases the volume and increase the pressure compared to the outside. This forces water through the gill and out of the operculum

Question 4

What is countercurrent flow

Answer 4

Blood and water flow in opposite directions

Question 5

Why is counter current more efficient than parallel flow

Answer 5

Because blood moving through the capillary in the lamellae is constantly meeting water which has a higher O2 concentration.

Question 6

Describe the countercurrent flow graph

Answer 6

• diffusion gardient is maintained all the way across gill lamellae and almost all the O2 from the H20 diffuses into the blood
• ensure equilibrium is not made

Question 7

Describe the parallel flow graph

Answer 7

• a diffusion gradient is only maintained for only half the distance of the gill lamellae so only 50% of all O2 from the water diffuses into blood

Question 8

How is SA made big

Answer 8

• two rows of filaments
• many lamellae
• many capillaries

Question 9

How CG made big

Answer 9

• counter current prevents equilibrium

- ventilation = constant flow

Question 10

How DD is small

Answer 10

• lamellae is 1 cell thick
• capillary’s walls 1 cell thick
• blood is close to the surface