The relationship between surface area to volume ratio and metabolic rate
Smaller organisms have a higher surface area to volume ratio. This means they lose heat faster and must run their chemical reactions — their metabolic rate — more quickly to compensate.
Formula
SA:V ratio = Surface Area ÷ Volume
Real World
A shrew must eat around 80–90% of its body weight in food every day because its tiny body loses heat so rapidly — its high SA:V ratio means metabolic rate must stay extremely high just to survive.
Exam Focus
When asked to 'explain', link SA:V ratio → heat loss rate → metabolic rate in a logical chain to earn all marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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