VIRUSES IN EVOLUTION Viruses are considered somewhere between life forms and inanimate objects by some researchers. Perhaps the one thing that viruses do that are most similar to life forms is that they contain genetic material that has the capacity to mutate over time. They have added to the diversity of all life forms because they add to the genome of these life forms. The diseases they cause also lead to changes in populations. Despite this, viruses themselves have confusing taxonomy that changes more dramatically than other types of organisms. Their evolution must be deduced because there are no fossil records. There are three prevailing views about the origin of viruses on earth. One proposes that viruses existed before cells and gave rise to cell life in general. They have unique genomes unlike the sequences seen in any life form. But because they need hosts themselves, cells are believed to have existed as long as viruses themselves in other theories on their origin. There is the belief that viruses essentially de-evolved or reduced themselves from more advanced parasites and is called the reduction hypothesis. This is supported by the fact that there are giant viruses overlapping cell life forms in some aspects. Still others suggest the “escape process”, meaning that viruses once escaped cellular genomes through horizontal gene transfer. It doesn’t explain, though, the uniqueness of their genomes. Viruses may have mediated the ability of eukaryotes to make RNA from DNA through transcription. Because of the major theories of viral evolution being so divergent, there are those that believe the true evolution of viruses has been a composite of these theories. Both megaviruses and mimiviruses are giant forms that have a partial ability to make what’s necessary for the translation process. Viruses have appeared to coexist along all evolutionary lines. It is possible that the last universal common ancestor of life in the universe gave birth to a minimum of two descendants. These were the last universal cellular ancestor and an archaic virocell ancestor. The cellular ancestor evolved into the different life forms, while the virocell ancestor did not evolve to have its own ribosomal machinery, forcing them to be cellular parasites.
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