Final answer:
Endotherms maintain a constant body temperature through internal heat production, unlike ectotherms that depend on the environment. 'Endothermic' is a word, while 'endothermal' is not commonly used, and 'endothermically' would be the adverbial form of 'endothermic'.
Step-by-step explanation:
An endotherm is an animal that maintains a constant body temperature in the face of environmental changes by generating internal heat. This heat keeps their cellular processes operating optimally, allowing for a stable level of activity even in cold environments. In contrast, ectotherms regulate their body temperature primarily through external sources, such as basking in the sun or seeking shade, which means their body temperature can vary with the environment.
Regarding the variations of the term "endotherm": "Endothermic" is commonly used in chemistry to describe a reaction that absorbs heat. "Endothermal" is not a commonly used term, but it could technically be used as an adjective to describe something relating to or denoting the absorption of heat. "Endothermically" could be considered the adverb form of "endothermic", describing the manner in which a process occurs.