Final answer:
Blubber is the adaptation that helps polar bears maintain a constant internal temperature in cold weather.
Step-by-step explanation:
The adaptation that helps polar bears maintain a constant internal temperature in cold weather is blubber. Blubber is a thick layer of fat that provides insulation and helps to retain heat. It acts as a natural insulator, preventing the loss of body heat to the surrounding environment. Polar bears have a thick layer of blubber, which helps them survive in the freezing Arctic temperatures.
Learn more about Polar bear adaptations