Large organisms, that have a small surface area to volume ratio, achieve the rate of gas exchange necessary to maintain life by having specialised gas exchange surfaces. These gas exchange surfaces all have a large surface area to volume ratio irrespective of the organism they are from.

E.g.

• Alveoli in the lungs of mammals have a large surface area to volume ratio meaning gas exchange in humans occurs at a fast rate.
• Gills in fish possess many filaments, which have a large surface area to volume ratio, as their surfaces are covered in lamellae.
• The leaves of plants, and the spongy mesophyll tissue in leaves, have a large surface area to volume ratio - meaning again - exchange is carried out more effectively.

Large organisms also often have a mechanism of ventilation. This is a means of maintaining the concentration gradients across the gas exchange surface. E.g. in humans breathing and blood flow maintain the concentration gradients across the gas exchange surface.