Argument continues over whether viruses are truly alive. According to the United States Code, they are considered micro-organisms in the sense of biological weaponry and malicious use. Scientists however are divided. They have no trouble classifying a horse as living, but things become complicated as they look at simple viruses, viroids and prions. Viruses resemble life in that they possess nucleic acid and can respond to their environment in a limited fashion. They can also reproduce by creating multiple copies of themselves through simple self-assembly.
Viruses do not have a cell structure, regarded as the basic unit of life. They are also absent from the fossil record, making phylogenic relationships difficult to determine. Additionally, although they reproduce, they do not metabolise on their own and therefore require a host cell to replicate and synthesise new products. However, bacterial species such as Rickettsia and Chlamydia, while living organisms, are also unable to reproduce outside of a host cell.
An argument can be made that all accepted forms of life use cell division to reproduce, whereas all viruses spontaneously assemble within cells. The comparison is drawn between viral self-assembly and the autonomous growth of non-living crystals. Virus self-assembly within host cells also has implications for the study of the origin of life, as it lends credence to the hypothesis that life could have started as self-assembling organic molecules.
If viruses are considered alive, then the criteria specifying life will have been permanently changed, leading scientists to question what the basic prerequisite of life is. If they are considered living then the prospect of creating artificial life is enhanced, or at least the standards required to call something artificially alive are reduced. If viruses were said to be alive, the question could follow of whether other even smaller infectious particles, such as viroids and prions, would next be considered forms of life.
Viruses do not have a cell structure, regarded as the basic unit of life. They are also absent from the fossil record, making phylogenic relationships difficult to determine. Additionally, although they reproduce, they do not metabolise on their own and therefore require a host cell to replicate and synthesise new products. However, bacterial species such as Rickettsia and Chlamydia, while living organisms, are also unable to reproduce outside of a host cell.
An argument can be made that all accepted forms of life use cell division to reproduce, whereas all viruses spontaneously assemble within cells. The comparison is drawn between viral self-assembly and the autonomous growth of non-living crystals. Virus self-assembly within host cells also has implications for the study of the origin of life, as it lends credence to the hypothesis that life could have started as self-assembling organic molecules.
If viruses are considered alive, then the criteria specifying life will have been permanently changed, leading scientists to question what the basic prerequisite of life is. If they are considered living then the prospect of creating artificial life is enhanced, or at least the standards required to call something artificially alive are reduced. If viruses were said to be alive, the question could follow of whether other even smaller infectious particles, such as viroids and prions, would next be considered forms of life.
, I was being cynical about our education.
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