Biodiversity

The biological variety and variability of life on Earth are referred to as biodiversity. Biodiversity is a measure of variety at several levels, including the genetic, species, and environment. A warm temperature and high primary production contribute to increased terrestrial biodiversity near the Equator, which is a consequence of the region's high primary productivity. Biodiversity is not uniformly spread over the globe, and it is particularly abundant in the tropics. Despite the fact that tropical forest ecosystems span less than ten percent of the earth's surface, they are home to around ninety percent of all known species. It is generally accepted that marine biodiversity is greater along coastlines in the Western Pacific, where sea surface temperature is greatest, as well as in the mid-latitudinal belt of all oceans. Biodiversity normally tends to congregate in hotspots, and although it has been rising through time, it is expected to decline in the future as a consequence of deforestation, which is the major cause of this. It includes the processes of evolution, ecology, and culture that are necessary for the continuation of life.

Rapid environmental changes are often responsible for major extinctions. It is believed that more than 99.9 percent of all species that have ever existed on Earth, a total of more than five billion species, have gone extinct. It is estimated that there are between 10 million and 14 million species on Earth at any one time, of which around 1.2 million have been recorded and more than 86 percent have not yet been described. The entire quantity of linked DNA base pairs on the planet is predicted to be 5.0 x 1037 and weighs 50 billion tonnes, according to current estimates. In contrast, it has been calculated that the entire mass of the biosphere may be as much as four trillion tonnes of carbon dioxide. In July 2016, scientists announced that they have discovered a group of 355 genes that belonged to the Last Universal Common Ancestor (LUCA) of all species that have ever lived on Earth.

The Earth has been there for approximately 4.54 billion years. The first indisputable evidence of life on Earth goes back at least 3.5 billion years, during the Eoarchean Era, after the previous molten Hadean Eon, when the Earth's geological crust began to harden after the earlier liquid Hadean Eon. Microbial mat fossils have been identified in sandstone that is 3.48 billion years old and was discovered in Western Australia. Another early physical evidence of a biogenic material is graphite, which was identified in meta-sedimentary rocks from Western Greenland that are 3.7 billion years old. In more recent years, in 2015, "remains of biotic life" were discovered in rocks in Western Australia that were 4.1 billion years old. According to one of the researchers, "If life evolved very fast on Earth... then it is possible that it is widespread across the cosmos."