Gas Exchange in Fish

What type do flow of water do fish have?

• Unidirectional flow of water

• Fish continuously pumps water through its mouth and over its gills

What are some problems with obtaining O2 from water rather than air?

• oxygen is not very soluble in water so there is a low concentration of oxygen in water than air

• water has a higher density than air so it’s harder to move over a respiratory surface during respiration

How does water travel through a fish?

What are flows through the mouth then through the gull flap the upper operculum then to the filaments which contain the lamellae and then the gill lamellae are surrounded by extensive blood vessels

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. (6 marks)

• Fish have many gill filaments which are also made of many gill lamellae.

• This increases the surface area of the girls in order to increase the rate of diffusion fish also have a concurrent system their blood and water flows in opposite directions.

• This increases the rate of diffusion because it maintains the concentration gradient along the whole gill lamellae.

• Furthermore in fish there is epithelial cells in the gill lamellae.

• This increases the rate of diffusion because it shortens the diffusion pathway for oxygen to travel to reach the blood fish are also adapted for efficient gas exchange because they have many filaments, increasing the surface area

• Circulation replaces blood saturated with oxygen

• Ventilation replaces water (as oxygen is removed)