B3 Exchange & Transport

Mammals

- The job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.

- To do this the lungs contain millions of little air sacs called the alveoli where gas exchange takes place

- The alveoli are specialisd to maximie the diffusion of oxygen and carbon dioxide.

-They have :

• An enormous surface area (about 75m^2 in humans)
• A moist lining for dissolving gases
• Vey thin walls
• A good blood supply

Fish

- the gills are the gas exchange surface in fish

- Water (containing oxygen) enters the fish through the mouth and passes out through its gills. As this happens, oxygen diffuses fro the…