Exchange Surfaces

• What does substance exchange depend on?

  surface area to volume ratio
• Exchange Surfaces adaption

  -thin membrane for short distance to diffuse

  -large surface area so lots of substances can diffuse at once

  -in animals they have lots of blood vessels to get in and out of the blood quickly

  -in animals they are ventilated so air moves in and out
• Gas exchange in lungs

  -to transfer oxygen to the blood and remove waste CO2

  -occurs in alveoli which are adapted for it
• Food exchange in small intestine

  has villi which are adapted
• Leaf gas exchange

  -Carbon dioxide diffuses into the air spaces then diffuses into cells

  -underneath the leaf has stomata which the CO2 diffuses into

  -oxygen and water vapor diffuse out