Question

What is the relationship between BMR and body size? Why?

a) Larger organisms have higher BMR due to increased surface area; smaller organisms have lower BMR.
b) Larger organisms have lower BMR due to increased surface area; smaller organisms have higher BMR.
c) BMR is independent of body size; it is solely dependent on the metabolic rate.
d) BMR increases proportionally with body size; smaller organisms have lower BMR.

Answer 1

BMR generally has an inverse relationship with body size on a per body weight basis, as smaller animals have a greater surface area relative to mass than larger animals.

Step-by-step explanation:

The relationship between Basal Metabolic Rate (BMR) and body size is such that smaller animals have higher BMRs when compared on a per body weight basis. This is because smaller animals have a greater surface area relative to their mass, leading to faster heat loss and the need for more energy to maintain a constant internal temperature. On the other hand, larger animals generally have lower BMRs per body weight, but in absolute terms, their overall energy requirements are greater to maintain their size.

Considering the options provided:

• (a) Larger organisms have higher BMR due to increased surface area; smaller organisms have lower BMR.
• (b) Larger organisms have lower BMR due to increased surface area; smaller organisms have higher BMR.
• (c) BMR is independent of body size; it is solely dependent on the metabolic rate.
• (d) BMR increases proportionally with body size; smaller organisms have lower BMR.

The most accurate response is that smaller organisms generally have higher BMRs per body weight because they have a greater surface area for their mass, therefore the correct answer is (b).