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Author
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Topic: Virus as transitional form?
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David
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Member # 1223
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posted 25. March 2004 12:33
INTRO: One objection to the theory of evolution suggests that no transitional forms between species have been identified, either in life today or in the fossil record. To me, there is a much greater gap that must be explained, that between non-living and living matter. One possible candidate to bridge this much larger gap is the virus, which has been described as existing on the "twilight of life".
As non-living substances, virus particles range in size from 50 to 1000 Angstroms, about the same size as colloids, and much smaller than bacteria. They have highly regular polyhedral shapes such that they can form single crystals that can be preserved almost indefinitely. These viral crystals can be analyzed by x-ray diffraction in exactly the same way inorganic crystals are analyzed. Under the right conditions, viruses can be dissolved to form solutions or dispersed in air.
As biologically active assemblies, viruses contain RNA or DNA, which carries genetic information specific to the virus, a trait shared by all living organisms. Once in a host organism, viruses can inject their genetic material into a living cell of the host. That genetic material then co-opts the cell's biochemical systems to produce innumerable copies of itself until the cell literally explodes, releasing those copies of genetic material to spread to more cells, leading to a geometric increase in viral particles. This is reproduction, another characteristic of living matter. Viruses are effectively predators/parasites that will consume the host unless the host's immune system can neutralize it. Viruses can mutate into different genetic strains as they spread through a population of host organisms, presumably in response to attacks by the immune system of the host. In this sense, viruses can adapt to changes in their environment, yet another trait of living organisms.
Questions:
1. Do viruses represent a transitional form between non-living and living matter?
1a. If yes, does this support current theories of molecular evolution?
1b. If no, what do viruses lack such that they do not meet the requirements for a transitional form?
2. Are viruses irreducibly complex?
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Scott
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Member # 1222
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posted 25. March 2004 21:16
2. Are viruses irreducibly complex?
It seems to me that "irreducible complexity" applies to "molecular machines" and not to whole organisms.
Aside from that technicality, if you can remove any component of a virus and still have a functional virus, that virus would not be "irreducibly complex."
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Scott
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Member # 1222
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posted 25. March 2004 21:21
1. Do viruses represent a transitional form between non-living and living matter?
It also seems to me that, given your description of a virus, a virus is dependent upon "living matter."
How then, could a "transitional form" be dependent upon that which it presumably is a transitional to?
regards
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David
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Member # 1223
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posted 26. March 2004 17:54
The weird thing about viruses is they are not quite "organisms". They are comparable in size to the smaller sub-components of bacteria for example, so in this case, by your suggestion, they could be irreducibly complex, as defined by Behe. (Personally, I am not convinced Behe's IC is a meaningful concept, but that is another thread.)
However, the issue of IC relates to whether or not viral particles could have been produced by some evolutionary chemical process on the path to living organisms. Your second comment is a good one, i.e. about how a virus could be a transitional form to life if viruses depend on living organisms to procreate. My response is to suggest that viruses may not have always operated this way, and how they may have procreated before the advent of life is unknown. Perhaps they are as we see them now after adapting to the presence of organisms in their environments. Or perhaps viruses are a consequence of life rather than a precursor to it.
Faithfully Yours,
David
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