SA:V Ratio & Metabolic Rate (AQA AS Biology): Revision Note

Surface area to volume ratio & metabolic rate

• The surface area to volume ratio of an organism is related to its metabolic rate

  • The metabolic rate of an organism is the energy expended by that organism within a given period of time

• This relationship exists because of the relationship between surface area to volume ratio and heat loss

  • Heat is lost to the environment at the body's surface, so having a large body surface in relation to volume will allow more heat to be lost

  • This means that:

    • small animals, with a higher SA:V ratio, will lose more heat to their surroundings, meaning that they need a relatively high metabolic rate to maintain body temperature

    • large animals, with a lower SA:V ratio, will lose less heat, meaning that they can maintain body temperature at a relatively low metabolic rate