Final answer:
Animals can be classified as either ectotherms or endotherms based on how they regulate their body temperature. Ectotherms depend on environmental heat and have fluctuating body temperatures, whereas endotherms generate internal heat to keep their body temperature constant, allowing constant metabolism and activity.
Step-by-step explanation:
Thermoregulation in Animals
Animals can be classified based on their thermoregulatory mechanism into two main categories: ectotherms and endotherms. Ectotherms are animals that do not internally regulate their body temperature; instead, they rely on environmental heat sources. Their body temperature fluctuates with the surrounding environment, which is why they are sometimes inaccurately referred to as 'cold-blooded'.
An example could be reptiles that bask in the sun to warm up or seek shade to cool down. On the other end of the spectrum are endotherms, which maintain a constant body temperature regardless of environmental changes. This is achieved through metabolic heat production from within the body. Mammals and birds are typical endotherms, with physiological adaptations such as fur, feathers, and fat layers for insulation or mechanisms like shivering and sweating to regulate body temperature.
Endotherms can sustain high levels of activity even when external temperatures are low, unlike ectotherms, whose enzyme activity and, subsequently, metabolic processes may slow down. This ability of endotherms to maintain stable internal conditions makes them homeotherms as well. It is important to note that although ectotherms are largely influenced by ambient temperatures, some have adapted to maintain thermal stability through behaviors or inhabiting stable environments, and are thus referred to as ectothermic homeotherms.