Question

Which animal has the highest metabolic rate/gram of body?

• A. Elephant
• B. Buffalo
• C. Shrew
• D. Sheep

Hint:

Metabolic Scaling: Smallest animal (SHREW) = Highest metabolic rate per gram. Largest animal (ELEPHANT) = Lowest metabolic rate per gram.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Allometric scaling and Kleiber's Law: mass-specific metabolic rate scales inversely with body mass ($ ext{BMR}/M \propto M^{-0.25}$), reaching the biological maximum in tiny mammals (pygmy shrew).
Key Formula or Approach:
\[ \text{Mass-Specific Metabolic Rate} = \frac{\text{BMR}}{M} = a \cdot M^{-0.25} \]

Step 2: Detailed Explanation:
In comparative animal bioenergetics and allometric scaling:
- According to the surface area-to-volume ratio and Kleiber's allometric law, smaller homeothermic animals have a much larger relative surface area per unit mass, losing heat rapidly.
- To maintain constant core body temperature, small animals have dramatically higher oxygen consumption and metabolic turnover per unit of tissue mass.
- The tiny Shrew (body mass $2 - 5\text{ g}$) has by far the highest mass-specific metabolic rate per gram of body tissue of all living mammals (consuming $> 100\times$ more oxygen per gram than an elephant).

Step 3: Final Answer:
Hence, the Shrew has the highest metabolic rate per gram of body, corresponding to option (C).