Special surfaces for exchange

• Large surface area - more space for molecules to pass (folding walls& membranes)
  
• Thin barrier- reduce diffusion distance
  
• Fresh supply of molecules of 1 side - keep conc. high for osmosis
  
• Removal of molecules on other side -keep conc. low for osmosis

e.g=

• small intestine (nutrients absorbed)
• liver (sugars in blood adjusted)
• root hairs of plants (minerals & H20 absorbed)

Lungs: 

• pair of inflatable structures in chest cavity

Air: Nose -->Trachea -->bronchi & bronchioles -->alveoli (walls of which= where exchange of gases takes place)

• protected by ribs (breathing helped by movement of ribs & diaphragm

o2 passes from air in alveoli --> blood in capillaries

co2 passes from blood --> air in alveoli

adapted for exchange:

• Large Surface Area
• Barrier permeable to 02 & CO2
• Thin barrier
• Fresh supply of CO2 from blood on one side, fresh supply of 02 from breathing on other side