3.1 surface area to volume ratio

Describe the relationship between the size of an organism and its SA:V

As size increases, SA:V decreases

Describe the relationship between the structure of an organism and its SA:V

More thin/ folded/ elongated structures increase SA:V

How to calculate SA:V

Surface area ➗volume

Why may SA:Mass be better than SA:V

Easier and quicker to find

More accurate due to irregular shapes

What is metabolic rate

Amount of energy used up by an organism within a given period of time

How can metabolic rate be measured

Measured by oxygen uptake as its used in aerobic respiration to make ATP for energy release

Explain the relationship between SA:V and metabolic rate

As SA:V increases, metabolic rate increases because…

• rate of heat loss per unit body mass increases

• So organisms need a higher rate of respiration

• To release enough heat to maintain a constant body temperature

How does the adaptation (changes to body shape) facilitate exchange

Increases SA:V and overcomes a long diffusion pathway

How does the adaptation (development of systems) facilitate exchange

• increases internal SA:V and overcomes a long diffusion pathway

• Maintains a concentration gradient for diffusion by ventilation/ good blood supply