What characterizes an ectotherm?

An ectotherm is characterized by its dependence on external temperatures to regulate its body warmth. Unlike endotherms, which generate and maintain a significant amount of internal heat regardless of their environment, ectotherms rely primarily on environmental sources to control their body temperature. This means that their metabolic activity and physiological processes can be heavily influenced by the temperature of their surroundings. For example, ectothermic animals such as reptiles and amphibians will bask in the sun to absorb heat when they need to raise their body temperature or seek shade to cool down when it is too warm.

The other characteristics listed do not apply to ectotherms. While some ectotherms can survive in extreme cold environments, this is not a defining characteristic and does not encompass the broader trait of relying on external temperatures for thermoregulation. Therefore, recognizing that ectotherms are fundamentally influenced by their environmental temperature is key to understanding their biological and ecological functions.