The Indians called the frozen peak of this great Alaskan mountain range Denali, or 'the high one.' Most know it as Mount McKinley. This preserved wilderness comes to life with the thaw of spring and wildlife abounds during the brief summer, only to succumb to the grip of the long winter. Watch as 5-week-old grizzly cubs play, a moose gives birth to her calf, and a wood frog survives the deep freeze of winter. Breath-taking shots of dazzling northern lights over vast and lush wilderness make this an unforgettable Eden.

As almost all animal inhabitants of Antarctica are forced to migrate north, the sea underneath the frozen ice still provides a home to many specially adapted fish whose cells are protected from freezing through an 'antifreeze' liquid. Many of them feed on the faeces of other animals. The most notable larger animal that does not migrate north is perhaps the Weddell Seal, which can be found as close as 1300 kilometres to the pole. Groups of seals tear holes into the ice to dive for food and come up to breathe. The females come back to the ice to give birth. This episode also describes primitive plant life such as lichen, which can still be found on the continent in winter, even in the extremely dry and permanently frozen valleys conditions under which dead animals can lie frozen for many centuries without decomposing. It details the life of the Emperor Penguin, 'the only birds to lay their eggs directly on ice'. While other animals retreat, Emperors migrate not just to the ice, but into the Antarctic continent. The females lay eggs which are incubated by the males under the harshest conditions on Earth (huddling closely together for warmth), while the females return to the sea.

The Red Sea is one of the youngest oceans in the world and one of the warmest. The northern region, with its diverse array of marine life, is one of the most visited dive locations on earth while the southern end remains virtually unexplored. It's a global hotspot for marine biology and an important trade route throughout human history, linking the trade goods of India and the Far East with the markets of Egypt and Europe.

The tropical Indian Ocean is home to the Spice Islands. Characterised by beautiful sandy beaches, fringing coral reefs and coastal mangrove forests, this is a vibrant nursery area for marine life, such as whale sharks, crabs, seahorses and a great variety of fish. The coastal areas are where humans have the most direct impact on the ocean's resources.

The Indian Ocean is the third largest body of water on Earth at more than 6,000 miles wide and covering 13% of the world's surface. It is home to 5,000 species of fish, many of which only exist in the Indian Ocean. But it is also an ocean under threat from global issues such as over-fishing and climate change, which make this an ocean on the edge.

With much of it covered in ice all year round and with no daylight from October to March, the Arctic Ocean is one of the world's most remarkable oceans. Its home to a multitude of unique life forms, all highly adapted to cope with the extreme and seasonal conditions. The impacts of climate change are more strongly felt here than anywhere else in the world.