Tropical rain forests are complex ecosystems, which are made up of four distinct environments. These "sub-ecosystems" are referred to as levels. In each level, animals and plants have adapted to the existing environmental conditions. The different levels are: the emergent level, the canopy, the understory, and the forest floor.
The emergent level is composed of trees, which may reach a height of more than 120 feet or more. The environmental conditions in which these trees survive include: wide variation in temperature, low humidity, strong winds, and the constant exposure to the sun's rays. Due to these harsh conditions the trees have adapted structurally to their environment. These adaptions include: hardwoods to absorb the gusts of strong winds, aerodynamic leaf structures which allows air to move around them, waxy leaves to retain water, photosynthetic activity during early morning and evening when humidity is high, and reproductive systems, such as flowers and fruits which take advantage of the winds for population and dispersal.
The canopy, just beneath the emergent level contains trees, which at maturity may grow 75 to 90 feet. The canopy is so dense that 80% of the sun's rays are blocked from reaching the lower levels of the rainforest. The trees of the canopy are exposed to many of the same harsh environmental conditions as the trees of the emergent layer, but because of the high density of plants, it does not seem as severe. Many of the animals found in this area live and eat the fruits, nuts, and leaves of the canopy trees.
The understory contains small trees and shrubs, which vary in height from about 10 to 20 feet. Some plants have adopted specifically to live their entire lives in the understory, while others are canopy or emergent trees that are waiting for the other trees to fall. When that happens, they quickly grow to their full height. Many animals live in the understory and feed on the abundance of fruits, leaves, and other animals.