Virus's: Life or non life?

Discussion in 'Biology & Genetics' started by paddoboy, May 20, 2020.

  1. paddoboy Valued Senior Member

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    I found the following, obviously reputable paper on viruses.


    https://www.nature.com/scitable/topicpage/the-origins-of-viruses-14398218/

    The Origins of Viruses
    By: David R. Wessner, Ph.D. (Dept. of Biology, Davidson College) © 2010 Nature Education


    Citation: Wessner, D. R. (2010) The Origins of Viruses. Nature Education 3(9):37

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    How did viruses evolve? Are they a streamlined form of something that existed long ago, or an ultimate culmination of smaller genetic elements joined together?

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    Figure 1


    To consider this question, we need to have a good understanding of what we mean by "life." Although specific definitions may vary, biologists generally agree that all living organisms exhibit several key properties: They can grow, reproduce, maintain an internal homeostasis, respond to stimuli, and carry out various metabolic processes. In addition, populations of living organisms evolve over time.


    Do viruses conform to these criteria? Yes and no. We probably all realize that viruses reproduce in some way. We can become infected with a small number of virus particles — by inhaling particles expelled when another person coughs, for instance — and then become sick several days later as the viruses replicate within our bodies. Likewise we probably all realize that viruses evolve over time. We need to get a flu vaccine every year primarily because the influenza virus changes, or evolves, from one year to the next (Nelson & Holmes 2007).

    Viruses do not, however, carry out metabolic processes. Most notably, viruses differ from living organisms in that they cannot generate ATP. Viruses also do not possess the necessary machinery for translation, as mentioned above. They do not possess ribosomes and cannot independently form proteins from molecules of messenger RNA. Because of these limitations, viruses can replicate only within a living host cell. Therefore, viruses are obligate intracellular parasites. According to a stringent definition of life, they are nonliving. Not everyone, though, necessarily agrees with this conclusion. Perhaps viruses represent a different type of organism on the tree of life the capsid-encoding organisms, or CEOs (Figure 1; Raoult & Forterre 2008).



    Where Did Viruses Come From?



    There is much debate among virologists about this question. Three main hypotheses have been articulated: 1. The progressive, or escape, hypothesis states that viruses arose from genetic elements that gained the ability to move between cells; 2. the regressive, or reduction, hypothesis asserts that viruses are remnants of cellular organisms; and 3. the virus-first hypothesis states that viruses predate or coevolved with their current cellular hosts.


    The Progressive Hypothesis

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    Figure 3

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    Figure 2

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    Figure 4


    The progressive and regressive hypotheses both assume that cells existed before viruses. What if viruses existed first? Recently, several investigators proposed that viruses may have been the first replicating entities. Koonin and Martin (2005) postulated that viruses existed in a precellular world as self-replicating units. Over time these units, they argue, became more organized and more complex. Eventually, enzymes for the synthesis of membranes and cell walls evolved, resulting in the formation of cells. Viruses, then, may have existed before bacteria, archaea, or eukaryotes (Figure 4; Prangishvili et al. 2006).
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    more at link............................


    extract:
    Summary:
    Contemplating the origins of life fascinates both scientists and the general public. Understanding the evolutionary history of viruses may shed some light on this interesting topic. To date, no clear explanation for the origin(s) of viruses exists. Viruses may have arisen from mobile genetic elements that gained the ability to move between cells. They may be descendants of previously free-living organisms that adapted a parasitic replication strategy. Perhaps viruses existed before, and led to the evolution of, cellular life. Continuing studies may provide us with clearer answers. Or future studies may reveal that the answer is even murkier than it now appears.
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    So [as illustrated in blue highlight] the question still abounds as to whether viruses constitute life as we know it, or non life.
    I have always wondered why some don't see them as life...glad that others also think the same.
    While understanding that science exists on stringent definitions, are they being to pedantic in not recognising viruses as life?
     
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  3. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Virus is alive but has period of inactivity until it can hijack (infect) a suitable cell to use for reproduction

    Homeless person (virus) is not a tenant (period inactivity) until can hijack (infect) accommodation (cell) to use for living (become a tenant)

    Not perfect translation equivalent but I contend close enough to get the gist

    My 2 cents

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  5. DaveC426913 Valued Senior Member

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    Part of the definition of life is that it has the capability of reproducing on its own. Viruses do not.

    It's not that it has a period of inactivity - it is that the virus, as a discrete unit, does not have the ability to reproduce itself.
     
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  7. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Fair point. Not sure when the official definition of life was first laid down, (before or after discovory of viruses) and to lazy to search, but perhaps definition needs to be updated

    it is that the virus, as a discrete unit, does not have the ability to reproduce itself.

    A virus, as a discrete unit, does have the ability to infect a cell and then proceed to reproduce

    I don't have the ability, as a descrete unit, to move at 60 km/hour, but on my motorbike, no problem

    Another thought occurred to me about this when (on another forum) discussing death

    I made the point NOBODY has ever been brought back from being dead, NOBODY. Near Death, YES, dead NO

    So I would contend a virus has a life cycle which has a period when it is Near Dead but not dead, hence alive

    Inability to reproduce itself as a discrete unit also applies to humans

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  8. paddoboy Valued Senior Member

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    While I agree with that sentiment, I also believe Michael has raised a valid point, and as per the paper, other reputable scientists also have reservations about its classification.
     
  9. paddoboy Valued Senior Member

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    Thanks Mick and Dave for a couple of interesting answers.
     
  10. DaveC426913 Valued Senior Member

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    Yeah, I think the ultimate answer - especially as we start exploring exobiology - is that there is a continuum, with a pretty fuzzy line between life and non-life.
     
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  11. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    Only Disney decides if all Viruses go to Heaven.

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  12. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Went looking for a reference where a jelly was fitted with EEG electrodes and produced a tracing which, when shown to other doctors, who were unaware of source, was not prepared to state the patient was brain dead and should be taken off life support

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  13. Write4U Valued Senior Member

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    Noooo......you cannot say we are discrete units. We have a few trillion cells which each have the ability to reproduce themselves. With a few exceptions. Specific parts of our entire biome are being copied at different rates;

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    Table 1: Cell renewal rates in different tissues of the human body. Values are rounded to one significant digit. Giving context through daily life replacement processes, we note that hair elongates at about 1 cm per month (BNID 109909) while fingernails grow at about 0.3 cm per month (BNID 109990), which is about the same speed as the continental spreading in plate tectonics that increases the distance between North America and Europe (BNID 110286).

    HOW MANY CELLS ARE THERE IN AN ORGANISM?
    http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves/
     
    Last edited: May 22, 2020
  14. Write4U Valued Senior Member

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    What parts of host cells do viruses use to replicate?

    See: Is consciousness to be found in QM in microtubules. (Alternative Theories subforum.)
     
  15. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Soooooo you are explaining CELLS are REPLACED (at various rates) not REPLICATING themself but after all cells have been REPLACED the body HAS reproduced itself?

    Ummmm need to flip a coin on that idea

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  16. Write4U Valued Senior Member

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    After the growing phase has stopped, old cells begin to die and are being replaced by new cells (copies). Thus except for a few permanent cell patterns, eventually all cells in your body are replaced. There used to be a very rough estimate that the entire body is replaced in about 7 years, but that's being disputed.

    Actually the human biome is a world in itself, not unlike the biosphere of the earth itself, seething and roiling with life and living, duplicating, energy converting biological patterns, ranging from single cells to the vital organs and the non-human cells of "bacterial "flora", all which function to keep the dynamic micro/macro-biome alive and vibrant.
    This video is a real time simulation of the mechanics of mitosis. It's astounding considering this is no more than a self-organized and evolved electro-chemical process of a living biome.
     
    Last edited: May 22, 2020
  17. Write4U Valued Senior Member

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    Or a deeper look at a complex living system.
     
  18. exchemist Valued Senior Member

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    Biome seems to be yet another word Write4U does not understand the meaning of. The human body is not a biome. It is a single organism.

    There is a human microbiome, which is the community of micro-organisms that lives in and on the human body, but is not part of it.
     
  19. Write4U Valued Senior Member

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    So wrong.
    Yes, and that little comment illustrates your ignorance of "living systems". (bolded red is mine)

    Human Microbiome
    Discovery Of The Human Microbiome
    https://www.britannica.com/science/human-microbiome
     
  20. Write4U Valued Senior Member

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    Bonnie Bassler demonstrates that viruses employ "quorum sensing" as well as bacteria.

    The secret social lives of viruses
    https://www.nature.com/articles/d41586-019-01880-6
     
  21. Write4U Valued Senior Member

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    On second thought.....I agree.......

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  22. James R Just this guy, you know? Staff Member

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    Do we need to create a dedicated thread to quarantine all your off-topic comments on "quorum sensing" as well?
     
  23. Write4U Valued Senior Member

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    Please educate me about the hard limitations in posting pertinent information.

    What is wrong with that piece of knowledge about the question of viruses are alive or not? I submit that this fact is very much a consideration of the OP question. Is intra-species communication of importance in the determination of what constitutes a living being? It is a recent scientific discovery of communication at the bacterial and viral level and currently a major concern during this current viral pandemic. Alive or not, viruses can talk to each other and tell when it is time to every member to become virulent. Kinda what we are experiencing here....

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    Do you really want to stay that superficial in probing the mysteries of life? Shall we stay at Trump's level of understanding life and what constitutes living?
     

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