Jungles provide the richest habitats on the planet - mysterious worlds of high drama where extraordinary animals attempt to survive in the most competitive place on earth. Flooded forests are home to caiman-hunting jaguars and strange dolphins that swim amongst the tree tops, while in the dense underworld, ninja frogs fight off wasps and flying dragons soar between trees. Acrobatic indri leap through the forests of Madagascar, while the jungle night conceals strange fungi and glow-in-the-dark creatures never filmed before.
The episode begins in the South American rainforest whose rich variety of life forms is used to illustrate the sheer number of different species. Since many are dependent on others for food or means of reproduction, David Attenborough argues that they couldn't all have appeared at once. He sets out to discover which came first, and the reasons for such diversity. He starts by explaining the theories of Charles Darwin and the process of natural selection, using the giant tortoises of the Galapagos Islands (where Darwin voyaged on HMS Beagle) as an example. Fossils provide evidence of the earliest life, and Attenborough travels a vertical mile into the Grand Canyon in search of them.
The incredible reef life and the birds, lizards and reptiles who cope with the lava rock islands of the Galapagos make this remote series of islands a unique natural habitat. The Panama and Humboldt currents regulate the seasons and the rhythm of life onshore and off.