Topic 4 -9

Question 1

What is the primary function of gills in fish?

Answer 1

Gas exchange

Gills allow fish to extract oxygen from water, which is essential for their survival.

Question 2

Why is gas exchange in water less efficient than in air?

Answer 2

Water is denser than air and contains much less O2 per litre

This results in slower O2 diffusion rates.

Question 3

What is the term for the one-directional flow of water over fish gills?

Answer 3

Ventilation of the gills

Question 4

Describe the sequence of events that pumps water across the gills in bony fish.

Answer 4

1. Mouth cavity pressure is reduced
2. Water enters through the mouth
3. Mouth cavity volume is reduced, pressure increases
4. Operculum opens, water exits

This process allows for effective gas exchange as water moves over the gills.

Question 5

What do cartilaginous fish, like sharks and rays, lack that bony fish have?

Answer 5

Operculum

Cartilaginous fish must swim constantly to maintain water flow over their gills.

Question 6

What are the thin branches on gill filaments called?

Answer 6

Lamellae

Question 7

How does the structure of gills facilitate gas exchange?

Answer 7

Large surface area and short diffusion path

The rich blood supply in lamellae enhances gas exchange efficiency.

Question 8

What is the purpose of the countercurrent flow system in fish gills?

Answer 8

To maintain a steep concentration gradient

Blood flows in the opposite direction to water, maximizing oxygen uptake.

Question 9

True or False: In a parallel flow system, equilibrium is reached between blood and water.

Answer 9

True

Question 10

Fill in the blank: The process that results in a continuous flow of water over the gills even if the fish is still is called _______.

Answer 10

Ventilation

Question 11

What happens to the buccal chamber during the process of ventilation?

Answer 11

It expands and contracts

This action helps to facilitate the movement of water over the gills.

Question 12

What is the role of the operculum in bony fish during ventilation?

Answer 12

Acts as a valve to control water flow

The operculum helps maintain pressure differences necessary for water to flow across the gills.

Question 13

What type of blood is found in the vessels flowing away from the gills?

Answer 13

O2-rich blood

Question 14

What is the significance of maintaining a countercurrent exchange in fish gills?

Answer 14

Maximizes oxygen exchange efficiency

This system ensures that blood always encounters water that is richer in oxygen.