Question

Small animals eat much more food per kg of body mass than do larger animals. The basal metabolic rate (BMR) is the minimal energy intake necessary to sustain life in a state of complete inactivity. The table lists the BMR, mass, and surface area for five animals. (a) Calculate the BMR/kg of body mass for each animal. Is it true that smaller animals must consume much more food per kg of body mass? (b) Calculate the BMR/m" of surface area. (c) Can you explain why the BMR/m \(^{2}\) is approximately the same for animals of different sizes? Consider what happens to the food energy metabolized by an animal in a resting state.

Short answer

a) Calculate the BMR/kg of body mass for each animal and verify the statement: "smaller animals must consume much more food per kg of body mass." b) Calculate the BMR per square meter (m^2) of surface area. c) Explain why the BMR/m^2 is approximately the same for animals of different sizes.

Step-by-step solution

Calculate BMR/kg of body mass

To calculate the BMR per kg of body mass, you will divide the BMR by the mass of the animal. Repeat this process for each animal. This will show the amount of energy required per kilogram of body mass.

Verify the statement

Compare the calculated values for BMR/kg of body mass for each animal. If the statement is true, the smaller animals must have higher values for BMR/kg than larger animals. This would indicate that they consume more food per kg of body mass.

Calculate BMR/m^2 of surface area

To calculate the BMR per square meter (m^2) of surface area, divide the BMR by the surface area of the animal. Repeat this process for each animal. This will show the amount of energy required per square meter of surface.

Analyze the BMR/m^2 values for each animal

Compare the BMR/m^2 values for each animal. Check if the values are approximately similar irrespective of the sizes of the animals.

Explain

To explain why the BMR/m^2 is approximately the same for animals of different sizes, consider that in a resting state, energy is mostly used to maintain a constant body temperature. For this energy to be lost to the environment, it must pass through the surface of the animal's body. Since the heat loss is proportional to the animal's surface area, and the heat generation (metabolism) is proportional to the mass, the ratio BMR/m^2 will remain approximately constant for different-sized animals with similar body temperatures.