Specialised Exchange Surfaces

Question 1

Increased surface area

Answer 1

Provides the area needed for exchange and overcomes the limitations of the SA:V ratio of larger organisms. E.g root hair cell in plants and villi in the small intestine.

Question 2

Thin layers

Answer 2

These mean the distances that substances have to diffuse are short, making the process fast and efficient, e.g alveoli in lungs and villi in small intestine

Question 3

Good blood supply

Answer 3

The steeper the concentration gradient, the faster diffusion takes place. Having a good blood supply ensures substances are constantly delivered to and removed from the exchange surface. This maintains a steep concentration gradient for diffusion. E.g the alveoli of the lungs, the gills of a fish and the villi of the small intestine.

Question 4

Ventilation to maintain diffusion gradient

Answer 4

For gases, a ventilation system also helps maintain concentration gradient and makes the process more efficient, for example the alveoli and the gills of fish where ventilation means a flow of water carrying dissolved gases.