Film directors Alastar Fothergill and Mark Linfied follow the movement of polar bears, elephants and humpback whales in their new film, Earth. Shot at 200 different locations in 64 different countries, Earth covers a vast terrain that ranges from the tops of mountains to the bottom of the ocean. The film was five years in the making.

Fothergill and Linfield also directed the BBC series Earth and the Discovery Channel series Planet Earth. The duo says that while the television series they directed were "habitat-based," the new film is "character-based."

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