The highest mountains on Earth are home to snow leopards, golden eagles, mountain goats, barnacle goslings, and gelada monkeys; only the toughest of animals can endure the extreme weather, scarce food supplies and limited oxygen on these peaks.

Delving beneath the surface of the Earth's oceans to uncover a world of extraordinary extremes, including crushing depths, stormy coasts, vast blue deserts, and crowded reefs; how seals fend off sharks; how orcas fight to survive.

In the grasslands, animals endure freezes, fires, floods, and droughts; bull elephants clash in mating battles; cheetahs and gazelles engage in a predator-and-prey dance in the Kenyan savanna; bison battle a blizzard while being pursued by wolves.

Jungles comprise the most diverse habitats on Earth in which only the most resilient species triumph; the fiercest jungle species include jaguars, caimans, gibbons, orangutans, spectral tarsiers, hummingbirds, and parasites.

Deserts are getting even hotter, drier and bigger, yet a host of remarkable animals still survive in the harshest of conditions, including cunning hyenas, pint-sized meerkats and sand-dwelling spiders.

The frozen poles are home to the planet's ultimate survivalists, including polar bears, penguins and Arctic wolves; their world is changing fast -- breaking apart under their feet -- and their resilience will be tested beyond the extreme.