Polar bears maintain homeostasis in freezing cold weather primarily through several adaptations, including:
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Thick Insulation: Polar bears possess a thick layer of blubber (fat) beneath their skin, which provides insulation against the cold. This helps to retain body heat and protect their internal organs.
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Fur: They have a dense, water-repellent fur coat, which also aids in insulation by trapping heat. The outer layer of fur is made up of long guard hairs, while the undercoat is softer and denser, providing additional warmth.
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Metabolic Rate: Polar bears can adjust their metabolism. They have a high metabolic rate that allows them to generate heat through the burning of stored fat, especially while hunting or when active. During periods of fasting or inactivity, they can enter a state of reduced metabolic activity to conserve energy.
Overall, the thickness of their fur and blubber plays a crucial role in retaining heat, while their ability to modulate metabolic rates helps them adapt to varying conditions. Thus, the best answer among the choices you provided would be: their thick fur retains heat and their thick skin insulates the internal organs against the cold (through subcutaneous fat), but their metabolism speeding up to produce heat is also a factor in maintaining homeostasis, especially during activity.
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