Delving beneath the surface of the Earth's oceans to uncover a world of extraordinary extremes, including crushing depths, stormy coasts, vast blue deserts, and crowded reefs; how seals fend off sharks; how orcas fight to survive.
The human eye is an amazing mechanism, able to detect anywhere from a few photons to a few quadrillion, or switch focus from the screen in front of you to the distant horizon in a third of a second. How did these complex structures evolve? Joshua Harvey details the 500 million year story of the human eye.
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.
The rains are late. It is the most brutal time of year. Babies born into drought face starvation. The weak and the injured are weeded out. Everything is desperate for rain. When it finally arrives, it is a downpour on an enormous scale. Alien creatures emerge into a different world. The wet season begins.
Liz Bonnin presents a controversial and provocative episode of Horizon, investigating how new scientific research is raising hard questions about zoos - the film explores how and why zoos keep animals, and whether they need to change to keep up with modern science, or ultimately be consigned to history. Should zoos cull their animals to manage populations? Liz travels to Copenhagen Zoo, who killed a giraffe and fed it to the lions, to witness their culling process first hand. They think it is a natural part of zoo keeping that is often swept under the carpet. Should some animals never be kept in captivity? In a world exclusive, Liz visits SeaWorld in Florida and asks if captivity drove one of their orcas to kill his trainer. But could zoos be the answer to conserving endangered species? Liz examines their record, from helping breed pandas for the wild to efforts to save the rhinos. She meets one of the last surviving northern white rhinos and discovers the future of this species now lies in a multimillion-dollar programme to engineer them for stem cells. Veteran conservation scientist Dr Sarah Bexell tells Liz the science of captive breeding is giving humanity false hope.
This is the ultimate hidden kingdom - the urban jungle. In the colourful and chaotic streets of Rio, a young marmoset is separated from his street gang and forced to confront of the dangers of the city alone. In the futuristic metropolis of Tokyo, a rhinoceros beetle escapes his captors and begins an extraordinary journey through this alien world to find sanctuary.