Just as humanity evolved under the glare of the equatorial sun on the East African savannah, it's no accident that many "hot spots" of biological significance occur along the equator. The equatorial sun is the most powerful source of energy on Earth, a force that reaches well beyond the equatorial band itself. As it beats down on the oceans, moist air rises on such a large scale that it generates the trade winds and great ocean currents that energize life on distant parts of the globe.

In this episode: The rainforests of Southeast Asia are a battleground. Here, the world's greatest diversity of species fights for light, food, and life. Fueled by the sun, rapid evolution encourages cunning and strategy to help plants and animals stake their claims in this complex environment.