The theory of Némesis, a star that orbits the Sun and causes catastrophic events is explored. Nemesis is a hypothetical red dwarf or brown dwarf, originally postulated in 1984 to be orbiting the Sun at a distance of about 95,000 AU (1.5 light-years) somewhat beyond the Oort cloud, to explain a perceived cycle of mass extinctions in the geological record, which seem to occur more often at intervals of 26 million years.

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.

Graham-Dixon reveals how the north of the country has produced some of the most dazzling and iconic art of the modern age. Spain's turbulent history has shaped artists from Francisco Goya to Pablo Picasso. Graham-Dixon argues that Spanish architecture is the art form now taking the nation forward in the new millennium.

Directed, produced, and narrated by Oliver Stone. In this episode we will see how the equation changes: specific month-by-month causes of the Cold War emerge and it is not entirely clear who started it. Highlights include Churchill's Iron Curtain speech, the civil war in Greece and the Red Scare that prompts the rise of Joseph McCarthy, the House Un-American Activities Committee and the FBI.

The Culture High is the riveting story that tears into the very fibre of modern day marijuana prohibition to reveal the truth behind the arguments and motives governing both those who support and those who oppose the existing pot laws. With budgets to fight the war reaching billions and arrests for simple possession skyrocketing to nearly a million annually, the debate over marijuana's legality has reached epic proportions. "The Culture High raises the stakes with some of today's biggest names, unprecedented access to footage previously unobtainable, and incredibly moving testimonials from both sides of the spectrum. Top celebrities, former undercover agents, university professors and a slew of unforgettable characters from all points of view come together for an amusing yet insightful portrait of cannabis prohibition and the grasp it has on society as a whole. "The Culture High" will strip search the oddity of human nature and dare to ask the question: What exactly is going on here?

The next instalment focuses on dietary needs and how different species have evolved beaks to suit their individual requirements. The latter come in a multitude of forms. Blue tits and goldfinches have beaks akin to tweezers, with which to extract seeds, while the hawfinch's razor-like bill can deal with a cherry-stone. However, the crossbill is the only finch that can twist its mandibles in opposite directions. Jays store acorns for winter by burying them in the ground, whereas woodpeckers can keep up to 60,000 of them in one tree trunk. Sap is also desirable, and there are a variety of methods used to obtain it. The hoatzin is the only specialised leaf-eater, and accordingly has a digestive system more akin to that of cattle. Plants recruit birds to aid pollination, and offer nectar as a reward. Hummingbirds eat little else, and the sword-bill's beak is the longest of any bird in relation to its body. Insects are also highly prized, and Galapagos finches are shown to possess some ingenuity as they not only strip bark, but also use 'tools' to reach their prey. Crows are hailed as being among the most intelligent birds, and one is shown using a twig to spear a grub within a fallen log. The robin is an opportunist, and Sir Attenborough observes one seizing morsels as he digs a patch of earth. In South America, a cattle tyrant sits atop an obliging capybara and uses its vantage point to spot passing food that may be dislodged by its grazing partner.