Segments 10 and 11 of the extraordinary BBC 11-part nature series. 40 camera teams were shooting at over 200 different locations all over the world for more than 5 years to get the pictures seen in the series. Each segment is followed by a sequence investigating the techniques and challenges of wildlife photography within that segment.

Seasonal forests: From the evergreen forest of the frozen North to the deciduous dry forests of the tropics, these woodlands illustrate the intense seasonality of the Earth. The tallest, largest and oldest organisms on the planet, they are home to a fascinating range of wildlife.

Ocean deep: Feast or famine: It's the governing principle of ocean life. From the sailfish, three-meter-long rapier-billed predators, and the exquisitely shelled Nautilus to the threatened blue whale, this journey into the most unexplored part of the planet reveals the extraordinary survivors of this immense and barren realm.