The two richest ecosystems lie in tropical rainforests and coral reefs. On land, tropical rainforests contain many species variation with an abundance of species in bird, mammals, amphibians, and plants. While tropical rainforests occupy only 7 percent of the Earth’s land area, they contain over half of the world’s species. This may be because species richness tends to increase with decreased elevation, increasing solar exposure, and increased precipitation; that is, hot, rainy low-land areas have the most species. In contrast, deserts have low species variation because of low precipitation. On earth, water is majorly important the equation for life. Many of the species are genetically isolated because of habitat size and variation in the build of the land (mountains, equator location, etc) such as seen in the Galapagos islands and the Amazon rainforest, both near and in South America.
