This programme focuses on birds. The feather is key to everything that is crucial about a bird: it is both its aerofoil and its insulator. The earliest feathers were found on a fossilised Archaeopteryx skeleton in Bavaria. However, it had claws on its wings and there is only one species alive today that does so: the hoatzin, whose chicks possess them for about a week or so. Nevertheless, it serves to illustrate the probable movement of its ancestor. It may have taken to the trees to avoid predators, and over time, its bony, reptilian tail was replaced by feathers and its heavy jaw evolved into a keratin beak.
Thanks to new technologies combining genetics, ethology, geology and even particle physics, paleontologists can now recreate the missing branches of the tree of life. Because of this, it has been discovered that prehistoric mammals were more varied and numerous than previously thought.
Ascends a kapok in the South American tropical rainforest to observe "the greatest proliferation of life that you can find anywhere on the surface of the Earth. There are two main causes for this: warmth and wetness. As this climate is constant, there are no seasons, so trees vary greatly in their flowering cycles.
The fifth programme explores the alliances formed between the animal and plant worlds. It examines the ways in which plants live together and rely on each other. Whether living together in harmony, relying on each other for homes, protection or food, or living off each other, by strangling or otherwise destroying each other in a bid to survive.
This special, narrated by Andrew Scott, celebrates the drama of Autumn and how animals and plants deal with the new challenges it brings. This is the time of year that brings the world's most spectacular transformations. With winter fast approaching, life has to get ready and that means feeding up while you can, fighting for the last chance to breed and rushing to grow up before the cold returns. While chipmunks and beavers dash to stash their winter supplies, many animals from musk oxen to beetles have to battle for mates and young gannets must face life's first dangerous challenges.