This episode looks at the influence of the sun and reveals how its seasonal journey affects the lives of all creatures.

Tour the mightiest mountain ranges, starting with the birth of a mountain at one of the lowest places on Earth and ending at the summit of Everest.

Fresh water defines the distribution of life on land. Follow the descent of rivers from their mountain sources to the sea. Watch spectacular waterfalls, fly inside the Grand Canyon and explore the wildlife in the world's deepest lake.

Caves are remarkable habitats with equally bizarre wildlife. Cave angel fish cling to the walls behind waterfalls with microscopic hooks on their fins. Cave swiftlets navigate by echo-location and build nests out of saliva. The Texas cave salamander has neither eyes nor pigment. Planet Earth gets unique access to a hidden world of stalactites, stalagmites, snotites and troglodytes.

12-01-2007, Around 30% of the land's surface is desert, the most varied of our ecosystems despite the lack of rain. Saharan sandstorms reach nearly a mile high and desert rivers run for a single day.

The Arctic and Antarctic experience the most extreme seasons on Earth. Time-lapse cameras watch a colony of emperor penguins, transforming them into a single organism. The film reveals new science about the dynamics of emperor penguin behaviour. In the north, unique aerial images show a polar bear swimming more than 100km. Diving for up to two minutes at a time. The exhausted polar bear later attacks a herd of walrus in a true clash of the Titans.

06-01-2007, Jungles cover roughly three per cent of our planet yet contain 50 per cent of the world's species. High-definition cameras enable unprecedented views of animals living on the dark jungle floor

06-01-2007, A humpback whale mother and calf embark on an epic journey from tropical coral paradises to storm ravaged polar seas.

05-01-2007, 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.

06-01-2007, Life goes to extraordinary lengths to survive this immense realm. A 30 tonne whale shark gorges on a school of fish and the unique overhead heli-gimbal camera reveals common dolphins rocketing at more than 30km an hour.