Biodiversity generally refers to the variety and variability of life on Earth. According to the United Nations Environment Programme(UNEP), biodiversity typically measures variation at the genetic, species, and ecosystem level.[1] Terrestrial biodiversity tends to be greater near the equator,[2] which seems to be the result of the warm climateand high primary productivity.[3] Biodiversity is not distributed evenly on Earth, and is richest in the tropics. These tropical forest ecosystems cover less than 10 percent of earth's surface, and contain about 90 percent of the world's species.[4] Marine biodiversitytends 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.[5]Biodiversity generally tends to cluster in hotspots,[6] and has been increasing through time,[7][8] but will be likely to slow in the future.[9]
Rapid environmental changes typically cause mass extinctions.[10][11][12] More than 99.9 percent of all species that ever lived on Earth, amounting to over five billion species,[13] are estimated to be extinct.lstimates on the number of Earth's current species range from 10 million to 14 million,[f which about 1.2 million have been documented and over 86 percent have not yet been described] More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[18]The total amount of related DNA base pairson Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes.[19] In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).[20] In July 2016, scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor (LUCA) of all organisms living on Earth.[21]
The age of the Earth is about 4.54 billion years.[22][23][24] The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago,[25][26][27] during the Eoarchean Era after a geological crust started to solidify following the earlier molten HadeanEon. There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.[28][29][30] Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland.More recently, in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia.[32][33] According to one of the researchers, "If life arose relatively quickly on Earth .. then it could be common in the universe.
decreased and then increased after major waves of mass extinctions Answer is.
Effect of small numbers of individuals on changes in the frequencies of an allele
Explanation:
By definition population genetics studies the changes in genetic variation of a population, this involves the modelling of changes in the frequencies of genes and alleles.
For example if an organism is born with a color that enhances its reproduction that population may change drastically in appearance, on the contrary if the allele causes a genetic disease, the population numbers might decrease.
Coal is a nonrenewable resource. It can be used for the generation of electricity as the burning of the coal as fuel liberates immense heat energy depending upon the carbon content of the coal. The amount of energy liberated by the coal depends upon the type of coal used hence, the energy yield can remain unpredictable. Wood is the source of biomass energy. It can be burned upon to obtain heat energy. The energy produce depends upon the carbon content and weight of the wooden logs used.
The energy harnessed by a wind turbine is also unpredictable because in a hot humid day and a wet rainy day wind energy cannot be captured.
