biodiversity

Biodiversity is the variability of life on Earth. It can be measured on various levels, for example, genetic variability, species diversity, ecosystem diversity, and phylogenetic diversity. Diversity is not distributed evenly on Earth — it is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are lat