Final answer:
Thicker fur aids in heat retention and white fur provides camouflage in the Arctic, while being unable to reproduce decreases a polar bear's fitness.
Explanation:
Fitness of a polar bear can be increased by having thicker fur as it helps in retaining body heat in the Arctic environment. White fur in polar bears acts as camouflage in snowy surroundings, aiding in hunting and escaping predators. In contrast, being unable to reproduce would decrease the fitness of a polar bear as reproduction is crucial for species survival and evolution.
Learn more about Polar bear adaptations according to Darwin's theory here:
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