Final answer:
The use of skeletal muscles by birds and mammals to generate heat is known as shivering thermogenesis, a mechanism essential for maintaining homeostasis by producing heat through involuntary muscle contractions.
Step-by-step explanation:
The use of skeletal muscles to generate heat in birds and mammals is referred to as shivering thermogenesis. This process is critical for maintaining homeostasis, particularly in response to cold environments. When the body temperature starts to drop, the nervous system triggers shivering, which involves rapid, involuntary contractions of the skeletal muscles. These contractions require energy, mostly derived from the breakdown of ATP (adenosine triphosphate). Muscles during exercise also produce heat, but it is the shivering response to cold that is specifically designed for heat production. This is a crucial survival mechanism in endotherms (warm-blooded animals) such as birds and mammals, enabling them to maintain a stable body temperature for optimal cellular function regardless of the ambient temperature.