Ectothermic refers to animals that rely primarily on external sources of heat to regulate their body temperature rather than generating sufficient internal metabolic heat. These animals, often called "cold-blooded," have body temperatures that vary with the environment, such as sunlight or warm surfaces

. Because ectotherms do not produce enough metabolic heat to maintain a constant internal temperature, they use behavioral adaptations like basking in the sun or seeking shade to thermoregulate. Examples include fishes, amphibians, reptiles, and many invertebrates

. Unlike endotherms (birds and mammals), ectotherms require less food but are more affected by environmental temperature fluctuations

. In summary, ectothermic animals depend on external heat sources to control their body temperature, which fluctuates with the surrounding environment rather than being internally regulated