Why Do Larger Organisms Need To Become Multicellular?

a) The table above helps us to understand why larger organisms need to become multicellular rather than just increase the size of their cells. The information in the table shows that as an organism gets larger in size, its surface area to volume ratio will decrease. However, the smaller the organism is, the greater its surface area to volume ratio will be. A small uncellular organism would have a large surface area in which diffusion (the movement of molecules) can take place. Diffusion is essential in order to supply oxygen and get rid of carbon dioxide across the outer cell surface membrane. However, as an organism gets bigger, its surface area to volume ratio gets larger therefore meaning that a specialised transport system is essential.