Final answer:
The arctic fox's winter white fur and summer brown fur are adaptations developed through natural selection to provide camouflage in various seasonal environments. Temperature-sensitive proteins cause fur color to change with temperature differences, with mutations that were advantageous for survival persisting in the species.
Step-by-step explanation:
During the winter, an arctic fox has white fur, and in the summer, it has brown fur. This change in fur color is primarily due to environmental adaptations that enable the fox to blend in with its surroundings, thereby increasing its chances of survival. The white winter coat of the arctic fox is an adaptation to the snowy environment, making the fox less visible to predators and prey amidst the snow. Similarly, the brown summer fur helps the fox to blend in with the summer tundra's rocks and vegetation.
Temperature-sensitive proteins play a role in this color change. These proteins cause the gene that controls fur color to produce a different color depending on the temperature. In colder temperatures, the protein does not fold correctly, leading to the white fur. In warmer temperatures, the normal folding of the protein results in brown fur. This mutation was advantageous for the species, aiding in their survival and propagation within their populations.
Furthermore, the trait of white fur is beneficial for animals such as arctic hares and ptarmigans in snowy environments, as it improves camouflage against predators like the arctic fox, indicating a similar evolutionary pressure. Natural selection favors the survival and reproduction of animals with traits advantageous to their environment, such as the white fur of the arctic fox during winter.