Tropicl rainforests are located across the world from Central America to Africa, Indonesia, Australia and Southeast Asia. Tropical rainforests have a wet climate and although, according to rainforestinfo.org, cover only 12 percent of the world's land area, more than half of the millions of the world's species live here. Tropical rainforests are so rich in biodiversity that less than 1 percent of their species have been studied by scientists.
The tropical rainforest is comprised of four layers of trees.The emergent layer has trees that are spaced wide apart and grow over 200 feet tall. These trees consist of broad-leaved, hardwood evergreens and have umbrella-shaped canopies. The trees of the upper canopy, which is the primary layer of the forest, grow to about 130 feet and have smooth leaves that allow rain to run off. The trees in the understory, or lower canopy, get little sunlight, so mostly shrubs, plants and small trees grow here. The forest floor is usually completely shaded, and since hardly any light penetrates it, few plants can grow at this layer.
The rainforest has an immense diversity of plants, but one thing many of the plants have in common is a "drip tip" or "drip spout," which allows rain, over 80 inches per year, to run off the leaves quickly. This feature helps to keep the leaf surface clean so branches don't get weighed down and break. Some of the plants that grown in the rainforest are orchids and bromeliads and over 2,500 species of vines including the rattan vine and lianas.
Insects, including butterflies, mosquitoes and colonies of ants, make up the largest single group of animals that live in rainforests. Just like plants, there is a great diversity of animals found in the rainforest, and many have adapted to a life in the trees, are brightly colored and eat a lot of fruits. Some of the animals found in rainforests include eagles, monkeys, bats, snakes, toucans, frogs, jaguars, leopards, sloths and giant anteaters.
According to the U.S. National Cancer Institute, of the 3,000 plants identified that are active against cancer cells, 70 percent are found in the rainforest. Thousands of fruits, of which hundreds are in use in the western world, grow in the rainforests, including bananas, coconuts, pineapples and mangoes. It is estimated that 50 to 90 percent of the world's species live in the rainforest, but extinction has been on a rise due to deforestation. Rainforests help control climate systems by releasing moisture into the atmosphere to produce rain. Furthermore, rainforests control flooding when soil soaks up moisture and releases it slowly, thereby moderating the flow of rivers. Many websites say that huge percentages of earth's oxygen are produced in rainforests, but that appears to not be true. "Earth's forests ... consume just as much of this gas as they produce," says Wallace S. Broecker in "Et tu, O2?"