Specialised Exchange Surfaces - the Alveoli

Question 1

Explain the need for exchange surfaces and transport systems in multicellular organisms.

Answer 1

• They have a smaller surface area compared to their volume, making it difficult to exchange enough substances to supply their whole volume across their outer surface
• Therefore, they need exchange surfaces for diffusion of these substances and transport systems to move them between exchange surface and rest of body

Question 2

The lungs transfer oxygen to the blood and remove carbon dioxide from it.

What helps them do this?

Answer 2

Alveoli

Question 3

State the function of the alveoli.

Answer 3

To allow gas exchange in mammals to occur

Question 4

Give the ways in which the alveoli are adapted for gas exchange.

Answer 4

• They have a moist lining for dissolving gases
• They have very thin walls, minimising the distance that gases have to move
• They have a large surface area