Why do smaller animals have higher mass specific metabolic r

Why do smaller animals have higher mass specific metabolic rates?

Why do younger animals use energy more efficiently?

Solution

Smaller  animals have a greater surface area for their mass than larger ones . Therefore,smaller animals lose heat at a faster rate than larger animals and require more energy to maintain a constant internal temperature. Therefore such animals have higher metabolic rate. This is because the higher metabolic rate of small animals needs a greater delivery of oxygen to tissues around the body.