Question

Why do most multicellular organisms require more than just diffusion to facilitate gas exchange? What is the other process called? Name all the places in our body where these two different processes occur (i.e. where do we get diffusion and where do we get the other process).

Answer 1

Surface area affects the rate of diffusion,the greater the surface area the more is the amount of gas exchanged. Therefore in multicellular organisms, gills or lungs are present to provide increased surface area for the required rate of gas exchange with outer environment. The distances between gas exchanger and deeper tissues are great for diffusion to meet the requirement so there is need of variety of respiratory surfaces.Respiratory surfaces is covered with epithelial cells to facilitate gas exchange.

The gas exchange is performed by lungs and respiratory system.

The oxygen through lungs is moved to bloodstream and red blood cells collect the carbon dioxide from body cells and transport to lungs to get it oxygenated. External respiration,the diffusion of oxygen from alveoli to capillary and diffusion of carbon dioxide from capillary to alveoli.Internal respiration occurs at body tissue level .