how do endotherms and ectotherms derive most of their body heat? multiple choice ectotherms derive most of their body heat through their environment, while endotherms derive most of their body heat through metabolic processes. both ectotherms and endotherms derive most of their body heat through their environment. ectotherms derive most of their body heat through their fur, while endotherms derive most of their body heat through insulating scales. ectotherms derive most of their body heat through metabolic processes, while endotherms derive most of their body heat through their environment both ectotherms and endotherms derive most of their body heat through metabolic processes.