2 Answers

  1. If you are interested in the actual state of affairs, then in modern biology, living means everything to which the methods of modern biology are applicable. Since the basis of modern biology is the theory of evolution, what is alive is something that can evolve.

    There is a very good definition of NASA – ” a self-sustaining chemical system capable of Darwinian evolution.”

    In general, definitions are usually given as follows: a set of phenomena is taken that intuitively clearly fall under a certain concept and on the basis of this set, criteria are developed that can be applied to disputed objects.

    Trees, fungi, and protozoa are all intuitively alive. What is typical for them? They reproduce, live, and die. They change as they evolve. They themselves maintain their existence, both in relation to individual specimens, organisms, and in relation to the species or population as a whole.

    All this is also true for viruses – a virus is born, a virus dies, a virus exists in the interval between these two events. The virus is multiplying. The virus evolves. The virus maintains its existence, both as an individual instance and as a population. That is, there are many more signs that the virus can be considered alive than there are signs that it is not alive. And what are these signs? Well, he doesn't have a metabolism. It's not cellular.

    But in any case, the most powerful argument is that the virus obeys the laws of biology, and not just biochemistry. And the fact that within the framework of the RNA hypothesis, it can be argued that the cell, as a being enclosed in its own shell, appears later than life, as a process. This is generally a very interesting point – life is already there, but there are no living beings yet. At this point, there are no viruses, but only RNA fragments that catalyze the synthesis of each other along complex chains – A catalyzes B, B catalyzes C and K, K catalyzes T, T catalyzes B and M, and M catalyzes A (this is a conditional example), which have yet to acquire proteins and ribosomes, like molecular machines for protein production – and all this precedes their own membranes. And now this whole structure is more complicated than simple biochemistry and can be considered as a living substrate.

    At the same time, it should be understood that definitions are made for the task and there may be other tasks in which the word “life” has a different meaning. When we need to separate not “what is studied by biology” from “what is not studied”, but “a living person “from” a dead person”, completely different criteria will be used and the ability to evolve will not be important here at all, because this criterion does not apply to an individual.

  2. I've read that there are viruses that one half of scientists think are alive and the other half think are dead. This is due to the difficulty of determining. Given that the living and the inanimate are a conditional division of the same matter (see materializim), we will never achieve an accurate objective definition in this matter.

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