Tropical rain forests can be described in two words: hot and humid. Mean monthly temperatures exceed 18 degrees C (64 degrees F) throughout the year. The average annual rainfall is lower than the 168 cm (66 inches) and can exceed 1000 cm (390 inches) though that it often lies between about 175 cm (69 in) and 200 cm (79 inches). High rainfall like this often make poor soil nutrients due to the easily soluble nutrients often drifted away.Tropical rainforests represent the level of very high biodiversity. About 40% to 75% of all species are indigenous creatures. The remaining rainforests are home to half of the living creatures and the whole of the planet's species. Two-thirds of all flowering plant species can be found in the rain forest. A hectare of rainforest can 42000 different insects, about 313 in tree species and 807 1500 plant species grow higher. Tropical rain forests are also known as "the world's biggest drug warehouse", because more than a quarter of natural medicines have been found there. It seems that the longer the millions of species of plants, insects and microorganisms are yet to be discovered in the tropical rain forests.Tropical rainforests are among the most threatened ecosystems around the world due to the large scale cut by human activities. Habitat fragmentation caused by geographical processes such as volcanic activity and the climate change that occurred in the past, and has been recognized as the key cause of speciation. However, habitat destruction caused by people suspected of being one of the main causes of the extinction of the species. Tropical rain forest was the target for the logging and deforestation to do large scale agricultural land throughout the 20th century, and the area covered by rainforests around the world are being shrunk rapidly. Tropical rain forest that existed on Earth hundreds of millions of years. Most of the tropical rain forest is today located on the array of the supercontinent Gondwana, the Mesozoic. The Mainland has caused huge losses in amphibian species, at the same time more dry climate has promoted the diversification of the reptiles. The Division was to leave the tropical rain forests in the world's main land: Latin America, Africa, Madagascar, Southeast Asia, and New Guinea, with a smaller section lies on the fringe of Oceania. However, the details of the origin of the rain forest is still uncertain because the fossil record is incomplete.
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