A temperate forest is composed of two or three, or at most ten dominant tree species, but a tropical rain forest may be composed of 100 or more species of trees. One may actually have difficulty finding any two trees of the same species within an area of many acres. Identify where this biome is located by studying the map showing  the biomes of the world.

 The dominant trees in the tropical rain forest are usually very tall and the tops interlace to form dense canopies. These canopies intercept much of the sunlight leaving the forest floor only dimly lit even at mid-day. The canopy, likewise, breaks the direct fall of rain. Hence, water drips from the canopy to the forest floor much of the time, even when no rain is actually falling. The canopy also shields the lower levels from wind, greatly reducing the rate of evaporation at ground level. The lower levels of the forest are consequently very humid. Temperatures near the forest floor are nearly constant.

 The pronounced differences in the conditions at the different levels within such a forest result in a striking degree of vertical stratification. Many species of animals and epiphytic plants (plants that grow on large trees), occur only in the canopy. Others occur only in the middle strata and still others occur only on the forest floor. Some vertical stratification is found in any community, particularly any forest community, but nowhere is it so extensively developed as in the tropical rain forest.

Approximately what percent of the Earth's total land area is tropical rainforest?

a. 6 percent

a. 20 percent

a. 50 percent

a. 75 percent