Explain briefly why an ectotherm uses much less energy than an equal size endotherm? Also explain why a small endotherm requires much more energy per kg weight than a bigger closely related endotherm species.
Ectotherms and endotherms differs on their source of heat to maintain their body temperatures. Ectotherms rely on external heat sources to maintain their temperature while the endotherms use internal body heat to maintain their body temperature. The endotherms use metabolic reactions and mechanical movements of muscles and tissues to generate heat. This the reason for which ectotherms use less energy than endotherm. While ectotherms depend on the environment to maintain their temperature endotherm needs more energy in order to generate heat and maintain their body temperature.