Exchange surfaces

• Exchange surfaces have adaptations to maximise exchange

  • Thin
  • Large SA
  • In animal - Lots of blood vessels
  • In gas - often ventilated
• Alveoli - gas exchange in the lungs

  • Enourmous SA
  • Very thin walls
  • A moist lining for dissolving gases
  • A good blood supply
• Villi - dissolved food molecules into the blood

  • Single layer of surface cells
  • Very good blood supply
  • Large SA
• Leaves

  • Thin
  • Large SA
  • Air spaces in the leaf for CO2 and O2 to move easily between cells
  • Lower surface is coverred in stomata = lets O2 and CO2 diffuse in and out + Water escape = Transpiration
• Root hairs

  • Large SA
  • Hairs stick out into the soil = maximises its SA
  • Higher concentration in the soil than the root hair cell = higher rate of osmosis
• Hypertonic = High concentration
• Hypotonic = Low concentration