Final answer:
An endotherm has a resting metabolic rate that is significantly higher than that of an ectotherm of the same size due to the internal regulation of body temperature, resulting in a higher energy requirement and BMR for endotherms.
Step-by-step explanation:
Typically, an endotherm has a resting metabolic rate that is substantially higher than that of an ectotherm of equivalent size. Endotherms, such as mammals and birds, regulate body temperature internally through metabolic processes, which increases their basal metabolic rate (BMR). For example, in a cold environment, an endotherm will produce more heat by raising its metabolic rate. In contrast, ectotherms, like fish and reptiles, rely on environmental temperatures to regulate their body heat, leading to a lower standard metabolic rate (SMR). Due to this internal heat production, endotherms have higher energy requirements and consequently a higher food intake to maintain a stable body temperature, which also reflects in their higher BMR compared to ectotherms.