Exchange surfaces

Question 1

Explain 3 ways that alveoli provide efficient gas exchange in the lungs.

Answer 1

There are many so provide a large surface area for exchange.
Have a moist lining to dissolve gases.
Have thin walls so there is a short diffusion distance.

Question 2

Explain how fish gills are adapted to their function.

Answer 2

Gills are made up of gill filaments which are in turn covered in lots of lamellae.
This increases the surface area for the exchange of gases between the blood and water.
Gills have good blood supply.
This provides a short diffusion distance between the water and blood.
The blood flows in the opposite direction to the water.
This helps maintain a concentration gradient for gas exchange.

Question 2

Explain the purpose of root hairs.

Answer 2

Root hairs increase the surface area of the roots so water and mineral ions can be absorbed efficiently from the soil.