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Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. [ 1 ] [ 2 ] Viruses have short generation times, and many—in particular RNA viruses —have relatively high mutation rates (on the order of one point mutation or more per genome per round of replication).
Viruses may even have multiple origins and different types of viruses may have evolved independently over the history of life. [52] There are different hypotheses for the origins of viruses, for instance an early viral origin from the RNA world or a later viral origin from selfish DNA .
Viral eukaryogenesis is the hypothesis that the cell nucleus of eukaryotic life forms evolved from a large DNA virus in a form of endosymbiosis within a methanogenic archaeon or a bacterium. The virus later evolved into the eukaryotic nucleus by acquiring genes from the host genome and eventually usurping its role.
Most virus species have virions too small to be seen with an optical microscope and are one-hundredth the size of most bacteria. The origins of viruses in the evolutionary history of life are still unclear. Some viruses may have evolved from plasmids, which are pieces of DNA that can move between cells. Other viruses may have evolved from bacteria.
In the eocyte hypothesis, the organism at the root of all eocytes may have been a ribocyte of the RNA-world. For cellular DNA and DNA handling, an "out of virus" scenario has been proposed: storing genetic information in DNA may have been an innovation performed by viruses and later handed over to ribocytes twice, once transforming them into bacteria and once transforming them into archaea.
The escaped DNA could have come from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria. [19] Coevolution theory Viruses may have evolved from complex molecules of protein and DNA at the same time as cells first appeared on earth, and would have depended on cellular life for many millions of years ...
Patrick Forterre has been working on a novel hypothesis, called "three viruses, three domains": [99] that viruses were instrumental in the transition from RNA to DNA and the evolution of Bacteria, Archaea, and Eukaryota. He believes the last universal common ancestor [99] was RNA-based and evolved RNA viruses. Some of the viruses evolved into ...
Bacteria are prokaryotic microorganisms that can either have a bacilli, spirilli, or cocci shape and measure between 0.5-20 micrometers. They were one of the first living cells to evolve [9] and have spread to inhabit a variety of different habitats including hydrothermal vents, glacial rocks, and other organisms.