4. SA:V

Question 1

Why are exchange surfaces needed?

Answer 1

Maintain a supply of materials that they need for respiration and growth:
* nutrients
* Oxygen

Remove the waste products of metabolism
* carbon dioxide
* ammonium
* urea

In large organisms, the body surface cannot act as a medium for exchange as the surce area to volume ratio is insufficient.

Question 2

Diffusion

Answer 2

Movement of molecules from regions of high concentration to regions of low concentration

Question 3

General features of exchange surfaces

Answer 3

• Large Surface Area relative to volume (SA:V)
• Permeable
• Thin as diffusion is efficient over short distances (<1mm)
• Moist as O2 and CO2 diffusion occurs in solution
• Mechanism to maintain diffusion gradients: Transport system, ventilation mechanism or creation of currents across surface (gas exchange)