specialised exchange surfaces

• what is an exchange surface?


  A part of an organism over which substances are exchanged with the environment 
• where are alveoli found?


  in the lungs
• The small protrusions of the lining of the small intestines are called villi. These have a large surface area which increases the area over which we can absorb nutrient molecules.

  
• what type of cell is shown in the image ?

  root hair cell

  
• what do root hair cells absorb from the soil?


  Water and minerals ions
• State and explain three features that most exchange surfaces have in common.


  One feature would be a large surface area allowing molecules to diffuse accross at the same time. A second feature would be that surfaces are premeable which means substances are only able to pass through the surface. A third feature would be that the surfaces are very thin which means substances only have to diffuse a short distance.
• State and explain three features of alveoli that make them good exchange surfaces. 


  1. There are lots of alveoli, giving a large total surface areab : lots can diffuse across at the same time
  2. Surfaces are permeable : Oxygen and carbon dioxide are able to diffuse across
  3. Good blood supply (good supply of 'internal medium') : Maintains a strong concentration gradient as blood is constantly replaced
• Which adaptation in plants contributes to the efficient exchange of gases?


  the flattened shape of their leaves