Tropical rain forests are forest biomes that occur close to the equator and experience high temperatures and significant amounts of rainfall each year. They may be evergreen or deciduous, and some are flooded during a portion of the year. Typically, rain forests feature tall old-growth trees that form a canopy high above the forest floor, with multiple levels of vegetation hosting animals and insects throughout.
Tropical rain forest biomes only cover about 6 percent of the Earth's surface, but they hold more than half of the animal and plant species on Earth. Most of the plants in the rain forest are various species of trees, with as many as 300 different varieties sharing space in a single hectare. The rain forest is also the primary source for 120 different prescription drugs. About two-thirds of the medicines shown to help fight cancer are entirely or partially derived from plants found there.
There are three major regions in the world where tropical rain forests exist. South America is home to the Amazon River basin and its surrounding rain forests, while the Indo-Malaysian rain forest zone extends from India through Southeast Asia to the shores of Australia. Africa is also home to rain forests that range from Zaire to Madagascar.