The Arctic ice cap first formed some three million years ago, providing a new habitat - polar pack ice - for mammals and birds to exploit. Seals and polar bears are now the primary inhabitants of this sea ice. The bears travel over it and the seals under, meeting at the seals' breathing holes, to the detriment of the seals! On land, plants tough enough to survive the Arctic cold form the habitat known as tundra. Because of the harsh climate and prolonged darkness, many animals migrate away from the dark Arctic for the winter, returning to take advantage of the 24 hour summer sunshine to breed.

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