Bony Fish

Question 1

Explain the mechanism of countercurrent flow.

Answer 1

Blood flows through capillaries in opposite direction to the water over the lamellar so the most oxygen can be absorbed from the water

Question 2

How are the gills adapted to carry out gas exchange?

Answer 2

Each Gill has 2 rows of gill filaments which are thin and many of them so they fold into secondary lamellae which provides a large surface area
The blood capillaries carry the deoxygenated blood close to the surface of the secondary lamellae which provides a short diffusion distance between blood and water
Blood maintains diffusion gradient
= faster rate of diffusion of oxygen and carbon dioxide

Question 3

Explain the process of ventilation in bony fish

Answer 3

The mouth opens which means water is drawn into the buccal cavity increasing the pressure and the buccal cavity floor lowers
Mouth closes water moves across the gills and out of the opercular cavity
Operculum opens and the water leaves
One direction flow

Question 4

Dissection of bony fish

Answer 4

Use fine scissors to remove operculum
Use scalpel to remove a section of the gill filament from the gill arch
Mount it in the centre of a microscope slide
Observe the gill filament using the x4 and x10 objective lens and identify the gill lamellae