The mighty Amazon River is the life blood of a forest. For half a year freshwater fish flourish in floodwaters that rise amongst the trees, then the waters retreat and the fish must face a six-month drought. The ancient Amazon has endured, and is both a time capsule for ancient animals and a hot house for the evolution of new species.

The Galapagos Islands are desert islands surrounded by an ocean oasis. Palmyra is an island oasis in the middle of a desert ocean. They lie half an ocean apart, yet both are shaped by the power of the Equator. Great ocean currents, set in motion by the force of the Equatorial sun, affect the destiny of animals living in both places

The Indonesian archipelago in the Indo-Pacific Ocean comprises thousands of islands, atolls and the largest concentration of coral reefs in the world. This rich and varied environment is a product of a unique set of natural circumstances. The equatorial sun powers ocean currents among the tiny dots of land. Where the archipelago meets the western tip of New Guinea an intersection of ocean currents creates perhaps the world's richest reefs in the region of the Rajah Ampat Islands. A coral reef houses a myriad of colours, shapes and patterns: from the bulb tentacle anemone which protects, and in turn is protected by, the brightly coloured clownfish; to the multi-branched gorgonian, home of the tiny pygmy seahorses. Coral animals have tiny symbiotic plants living within their tissues. Brought together by sunlight, it is one of the most powerful biological partnerships on earth. Young coral ingest free-swimming algae, but because of some ancient genetic signal, the algae are not eaten. Instead the coral wraps the tiny plants in membrane and moves them to tissues exposed to light. The algae are nourished and in response produce sugars that both they, and the coral, consume increasing the corals growth rate. Coral is far from a passive inhabitant of the ocean and once a year many species combine for an event that is both spectacular and of scientific intrigue. A mass spawning, which usually occurs during a full moon, provides not only a breeding opportunity, but also inter-breeding between coral species. It is this ease and adaptability of hybridization that is leading scientists to re-examine the most basic elements of what comprises a species.

For much of the year the African Savannah bakes under the oppressive Equatorial sun. The dryness is unusual for the Equator, whose regions are often covered with dense rainforests and associated with a seasonless annual cycle. Thirty million years ago part of east Africa was torn apart. Massive volcanic activity combined to form the beginnings of what would be the Great Rift Valley. Over millions of years the valley widened and grew longer, spreading north and south for more than 4,500 kilometres. The resulting mountain ranges rose 3000 metres, blocking clouds coming from the west and creating a rain shadow over east Africa. The vegetation became drier and gradually the rainforests that once covered the continent began to disappear. In its place grasslands would develop, grasslands that would profoundly change life at the Equator forever. These Carbon 4 or C4 plants had developed a revolutionary pathway for transforming sunlight and carbon dioxide into sugars. These turbo-charged plants now feed the many species of herbivore that migrate to the Savannah each November after rains feed the drought-stricken land. The ungulates have a secret weapon that allows them to eat the tough C4 grasses: they have evolved four-chambered ruminant stomachs. The Savannah is inhabited great cats, each with their own adapted modes of predation. The leopard uses stealth and camouflage, and if the hunt is successful it will retreat to the security of the trees away from the many scavengers who inhabit the grasslands. More than any other great cat, the lion has been most shaped by living under the Equatorial sun. Lions are social rather than solitary, organised and controlled by the females while the males live on the margins of the group. The blazing sun could kill them if they overheated, so they hunt collectively in the cool of night.

In the high Andes of Ecuador the intense power of the equatorial sun beats down through thin air onto a grassland world fringed by glaciers and cloud forest. Every day is like summer, and every night is like winter. Within just 24-hours plants and animals must cope with both freezing and over-heating.

The rainforests of South East Asia are a battleground. Here, the greatest diversity of species in the world fight for light, for food and for life. Fuelled by the sun, rapid evolution encourages cunning and strategy to help plants and animals stake their claims in this complex high-rise world.