The relationship of surface area to volume is the most important factor that determines how size influences the design of organisms contact between an organism and its environment occurs at the surface area, whereas the internal workings are related to its volume or mass the two quantities are not related in a simple proportionality - you cannot simultaneously double the surface area and volume of an organism unless you change its shape drastically. In both cases, the formula for area is the length of something squared, and the formula for volume is the length cubed. In general, for isometric objects areas are proportional to L 2 and volumes proportional to L 3 . Isometric objects are those that vary in size while retaining the same shape. Therefore, Surfaces are proportional to the squares of lengths.
Volumes are proportional to the cubes of lengths.
This means that a larger object will have less surface relative to its volume than will a smaller isometric object of the same shape. A whale is big inside with little outside, and a bacteria is big outside with little inside. In nature, there must be an increasing deviation in larger organisms from being spherical if processes that use surfaces must be held constant. This equation is often called the allometric equation. In other words, larger animals are more rotund, and smaller ones are more elongate.