BIODIVERSITY

8804 WORDS

Rainforests are an example of biodiversity on the planet and typically possess a great deal of species diversity. This is the Gambia River in Senegal's Niokolo-Koba National Park.

Biodiversity is the degree of variation of life.[1] It is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation (number of species)[1] within an area, biome, or planet. Terrestrial biodiversity tends to be highest near the equator,[2] which seems to be the result of the warm climate and high primary productivity.[3] Biodiversity is not distributed evenly on Earth. It is the richest in the tropics. Marine biodiversity tends to be highest along coasts in the Western Pacific, where sea surface temperature is highest and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity.[4] Biodiversity generally tends to cluster in hotspots,[5] and has been increasing through time[6][7] but will be likely to slow in the future.[8]Rapid environmental changes typically cause mass extinctions.[9][10][11] One estimate is that <1%–3% of the species that have existed on Earth are extant.[12]The earliest evidences for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland[13] and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.[14][15] Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion—a period during which the majority of multicellular phyla first appeared.[16] The next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of plant and animal