What defines ectotherms?

Ectotherms are organisms that primarily rely on external environmental sources to regulate their body temperature. This means that their internal temperature fluctuates with the temperature of their surroundings. For example, reptiles such as lizards bask in the sun to warm up and move to shade or burrows to cool down, demonstrating their dependence on the external environment for thermoregulation.

This definition highlights a fundamental characteristic of ectotherms, distinguishing them from endotherms, which can maintain a relatively constant internal temperature regardless of external conditions through metabolic processes. Understanding this concept is crucial in the study of physiology and ecology, as it impacts how ectothermic organisms interact with their habitats, their behavior, and their survival strategies in varying climates.