Here's why:
* Endothermy refers to the ability to regulate body temperature internally. Mammals are warm-blooded, meaning they maintain a constant internal body temperature regardless of the external environment. This is achieved through metabolic processes.
* Fish and amphibians are ectothermic, meaning they rely on external sources of heat like the sun to regulate their body temperature. Their body temperature fluctuates with the environment.
Let me know if you'd like to know more about homeostatic conditions in mammals!