Final answer:
The ground squirrel is the largest animal to undergo true or deep hibernation, where it experiences a significant decrease in body temperature and metabolic rate, unlike bears that enter a state of deep sleep without dramatic changes in their physiology.
Step-by-step explanation:
The largest animal to undergo true or deep hibernation is the ground squirrel. When we discuss hibernation, we refer to a state of torpor over a long period, such as winter. Hibernation is different from the deep sleep that larger animals like bears undergo. Unlike bears, ground squirrels and other small hibernating animals experience a significant decrease in body temperature and metabolic rate. This adaptation allows them to conserve energy during times when food is scarce. Body processes in these smaller animals slow significantly, and their body temperature can drop to nearly freezing, while bears maintain a body temperature at or near their normal level and can be awakened more easily.
True hibernation is an example of how animals achieve homeostasis, where they maintain a dynamic equilibrium in response to extreme environmental conditions. This state is crucial for animals to survive long periods without food, and it exemplifies their incredible ability to adapt to seasonal changes.