The fifth programme explores the alliances formed between the animal and plant worlds. Attenborough dives into Australia's Great Barrier Reef and contrasts the nocturnal feeding of coral, on microscopic creatures, with its daytime diet of algae. Some acacias are protected by ants, which will defend their refuge from any predator. Besides accommodation, the guards are rewarded with nectar and, from certain species, protein for their larvae as well. Fungi feed on plants but can also provide essential nutriment to saplings (Mycorrhiza). The connection is never broken throughout a tree's life and a quarter of the sugars and starches produced in its leaves is channelled back to its fungal partners. Meanwhile, fungi that feed on dead wood leave a hollow trunk, which also benefits the tree. Orchids enjoy a similar affiliation. Lichens are the product of a relationship between fungi and a photosynthetic associate, usually algae. They are extremely slow-growing, and a graveyard is the perfect location to discover their exact longevity. Mistletoe is a hemiparasite that obtains its moisture from a host tree, while using own leaves to manufacture food. Its seeds are deposited on another by the mistletoe tyrannulet, following digestion of the fruit. The dodder (Cuscuta) is also parasitic, generally favouring nettles, and siphons its nourishment through periodic 'plugs' along its stem. The rafflesia has no stem or leaves and only emerges from its host in order to bloom — and it produces the largest single flower: one metre across.

The key to understanding the universe seems to be understanding its smallest components. But the quantum realm bears little resemblance to the universe we know. Image a particle that can be many places at the same time and communicate changes instantly across vast distances, even to the other side of the Universe. Shrinking down billions of times, into the realm of atoms and sub-atomic particles, takes us into a bizarre world of paradoxes and multiverses. Explore with us quantum physics and the potential applications in computer science.

A constellation is a group of stars that are connected together to form a figure or picture. Explore some of the 88 official constellations and learn about some of the highlights of each.

An epic true story set against the backdrop of one of the wildest places on Earth, African Cats captures the real-life love, humour and determination of the majestic kings of the savannah. Narrated by Samuel L. Jackson, the story features Mara, an endearing lion cub who strives to grow up with her mother’s strength, spirit and wisdom; Sita, a fearless cheetah and single mother of five mischievous newborns; and Fang, a proud leader of the pride who must defend his family from a rival lion and his sons.

This scientific detective tale tells the story of a remarkable group of pioneers who wanted to reach the ultimate extreme: absolute zero, a place so cold that the physical world as we know it doesn't exist, electricity flows without resistance, fluids defy gravity and the speed of light can be reduced to 38 miles per hour. Absolute zero became the Holy Grail of temperature physicists and is considered the gateway to many new technologies, such as nano-construction, neurological networks and quantum computing. The possibilities, it seems, are limitless. The first episode Chronicles the major discoveries leading towards the mastery of cold, beginning with King James I's court magician, Cornelius Drebbel, who managed to air condition the largest interior space in the British Isles in 1620. Other stories will include the first "natural philosopher," Robert Boyle, a founder of the Royal Society in Great Britain; the Grand Duke Ferdinand II de Medici's involvement in the creation of the first thermometer; the establishment of the laws of thermodynamics by three young scientists, Sadi Carnot, James Joule and William Thomson; and Michael Faraday's critical achievement in liquefying several other gases which set the stage for the commercial application of cold to refrigeration and air conditioning.

An apocryphal view on the pyramids, starting in awe at the amazing achievement of the Pharaonic architecture and sculpture, most specially at Gizeh, given Cheops's pyramid's size, weight, incredibly precise carving, four pairs of slightly shifted half sides, stunningly precisely measured shapes and symmetry. Then it questions and challenges conventional Egyptology beliefs, which it calls unproven or even impossible to verify, such as the absence of machines, a wharf duration of only 20 years or accidental equinox-orientation. Next it elaborates the theory that other major pyramid technology sites in Precolombian America, Easter Island and China can't coincidentally lie on two lines intersecting at Gizeh, even if not contemporaneous and without known contacts in their ages, and have several improbable things in common, like some of their cultures. Elaborate mathematical theories and measurements indicate the Egyptians must have known some astronomy, pi and the golden number