Final answer:
All living bipeds are endotherms, which means they maintain a constant internal body temperature through internal metabolic processes. This trait allows them to be active across various environmental temperatures and is seen in both mammals and birds.
Step-by-step explanation:
The question you've asked concerns which type of animals are considered bipeds that maintain a constant internal body temperature. Specifically, if all living bipeds are endotherms, ectotherms, heliotherms, or poikilotherms. The correct answer is endotherms. Endotherms are animals that regulate their own body temperature through internal processes, allowing them to stay active in cooler environments, unlike ectotherms who rely on external temperatures. Animals such as mammals and birds are endotherms and are also bipedal in many cases (like humans and birds). These animals have evolved to maintain a constant internal body temperature regardless of environmental changes, which supports high metabolic activity and allows for adaptation to various climates.