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.
The third instalment examines the spiders and others that produce silk. Attenborough visits New Zealand's Waitomo Caves, which are inhabited by fungus gnats whose illuminated larvae sit atop glistening, beaded filaments to lure their prey.
The Taiga forest, on the edge of the Arctic, is a silent world of stunted conifers. The trees may be small but filming from the air reveals its true scale. A third of all trees on Earth grow here and during the short summer they produce enough oxygen to change the atmosphere.
In the second episode; India is a subcontinent surrounded by mountains. We explore the little-known Western Ghats at the edge India's south. Here are Monsoon hills covered in lush forests and tea gardens which shelter some of the greatest biodiversity in the world. But far to the north lies the mighty Himalayas - so vast they drive the climate by capturing the monsoon winds and protect India from the northern chill. It's a unique world full of life.