Will explore the strategy, deception and feats of engineering plants use to thrive in the changing weather of different seasons. In the face of conditions ranging from ice and snow to raging fires, survival is often a question of perfect timing - particularly when contending with intense competition and surprising predators.
In this episode, David Attenborough travels to Finland to show one of the most extreme examples of seasonal plant life in the Arctic Circle. He also travels to California to see how climate change is affecting giant sequoias. These ancient trees like all other seasonal plants depend on the predictability of the seasons and our current changing climate threatens their survival.

Antarctica is the most hostile of all earth’s frozen worlds. Yet even here, amongst some of the most challenging conditions on the planet, life finds a way not just to survive, but thrive.
Our journey begins at the far edge of the continent, on its far-flung sub-Antarctic islands. Here we meet king penguins that, to feed at sea, must face the danger of ferocious leopard seals lurking in the shallows. On another island, we witness for the first time male Antipodean wandering albatross partnering up with each other as the females in their population are disappearing due to fishing activity.
Heading towards the continent of Antarctica, we traverse the roughest seas on earth - the Southern Ocean - where we find the rarely filmed Antarctic blue whale, the largest animal to have ever lived. At the edge of Antarctica, the sea is so cold that it freezes over, creating a vital ice platform for a mother Weddell seal to raise her precious pup. Still, she needs to protect him from aggressive males.
In spring, the coast of Antarctica is free of snow, drawing in thousands of breeding chinstrap penguins. Stones are at a premium to build their elevated nests and protect chicks from meltwater. But stealing is commonplace, and to make matters worse, with climate change we find chicks today shivering with hypothermia – a warming Antarctica means increased meltwater. Other residents are facing an uncertain future too, including wave-washing killer whales. We discover that their favourite prey, Weddell seals, are now harder to reach, so instead they are resorting to targeting much more feisty prey, including leopard seals, an apex predator in its own right. This dramatic encounter has never been filmed before.
Travelling into the interior of the continent - into the frozen heart of Antarctica - we find great surprises. This is one of the most volcanic regions on earth, and one of the driest. We reveal unexpected sand dunes, hidden in a rare ice-free valley. Then, on the exposed mountain tops, sticking out from the otherwise ice-covered interior, we find tiny snow petrels, which raise their chicks further south than any other bird, and defend their territory by projectile vomiting!
The greatest revelation lies deep in the interior, beneath the surface of an ice-covered lake, where we discover ancient alien-like structures - giant stromatolites - built by primitive lifeforms. If life can make it here, in the extremes of Antarctica, it raises the possibility that life can exist elsewhere, including in the frozen lakes of distant planets.

In the far north of our planet lies the largest land habitat on earth, home to snow-covered forests and the icy open tundra. These are lands of extremes that push animals to their limits: in winter they are so cold that much of the ground has remained frozen since the last ice age. To stand any chance of survival, animals must adapt in extreme ways: here a super pack of wolves, 25 strong, has come together to take on the only large prey available to them in winter, American bison.
On the featureless tundra, an Arctic fox must strike a living alone. She is a wanderer and will roam many hundreds of miles searching for tiny lemmings, hidden deep underground. The only way to reach them is with a head dive. In the remote far east of Russia, a rare Amur leopard prowls the seemingly empty, snow-covered forest. With little prey available, it must use its ingenuity to find a meal. It follows crows in the hope of finding carrion, but it must not stay long, for it shares the forest with a far larger but equally hungry big cat, the Siberian tiger.
As spring arrives, the forests begin to thaw and life returns. Beneath the ground, a nest of tiny painted turtle hatchlings now emerge, having remained frozen in a state of suspended animation throughout winter. To the north, it is a further month before the sun’s warmth baths the frozen ground of the tundra. Tucked away underground lies a tiny snow queen – a Lapland bumble bee. She is the sole survivor of her colony - the rest perished in the winter freeze - but her larger size, her furry body and antifreeze in her blood have allowed her to survive. Now she is in a hurry. She must feed herself and raise a brood in the brief window of summer while the flowers are in bloom.
Snowy owls also use the open tundra to breed: one pair have raised a nest full of fluffy chicks. With 24-hour daylight in which to hunt, the dedicated parents bring back meal after meal for their ever-growing brood. But one day, they return to find the nest empty.
Today, the biggest challenge in the tundra is climate change. Warming summers are melting the permafrost deep within the soil, causing the ground to thaw and, in places, the land to collapse. These changes are impacting the animals too. Caribou arrive in herds of 200,000 individuals to raise their calves in the rich pastures, but warming means mosquitos emerge sooner and bother the calves before they have had a chance to gain strength. The parents drive their young to cooler, mosquito-free land, but to get there they must cross rivers running with increased meltwater and escape hungry grizzly bears. They, like much of the tundra's wildlife, are adapted to live in the extremes - but the challenge of today’s warming climate could be one extreme too many.

To maximize longevity, you might think it’s best to play it safe and stay cozy. But some scientists believe we should do the opposite, as exposure to extreme temperatures can trigger our bodies’ own defenses against the killer diseases of old age. Chris heads for the freezing Arctic with his brothers Liam and Luke to take on the ultimate cold therapy.

As Chris bulks up for ‘Thor: Love and Thunder’ he needs to build a body that looks right for an immortal god. But, he also wants the kind of muscles that are scientifically proven to help him stay strong and healthy as he grows older in real life. Teaming up with extreme sports guru Ross Edgley, he trains for a grueling 100-foot rope climb challenge, changing him from an ornament into an instrument.

Over the past year, Chris Hemsworth have been exploring the science of living longer, doing everything he can to hold back time. But whatever he does, sooner or later, aging and death will win. Now Chris is facing his most extreme and emotional challenge: three days in a retirement village while wearing an aging suit that turns the simplest activity into a Herculean task. He'll be carrying an extra 30 pounds around and shoes that will make him unbalanced, apart from glasses to see improperly and acoustic earmuffs. Later on, Chris is going to do a death-bed meditation. He’s testing the theory that the best way to combat aging and fear of mortality might not be to fight it but accept it,