diffusion in living organisms 1.3.1

• the bigger the total volume, the smaller the surface area to volume ratio is
• shapes with smaller surface area to volume ratio will have slower rates of diffusion
• shapes with a larger surface area to volume ratio will have faster rates of diffusion
• shapes with a large volume can increase their rate of diffusion by increasing the surface area
• an exchange surface is a location where materials are transferred between an organism and its environment
• a transport system is a structure that moves materials around the body of a multicellular organism
• without exchange surfaces or transport systems, large organisms would be unable to sustain themselves as diffusion would be too slow to provide them with the necessary nutrients as the surface area to volume ratio would be too small
• single celled organisms are able to rely on diffusion because the surface area to volume ratio is large.
• alveoli have a large surface area, a good blood supply and a short diffusion distance
• alveoli walls are only one cell thick and breathing maintains the concentration gradient
• small intestines have a large surface area, good blood supply and a short diffusion distance
• microvilli in the small intestines further increase the surface area