I do not agree with considering viruses as not alive.
A viral particle outside its host can be considered dead, in the sense that it is inert and it does not have any metabolism, but it is not definitively dead, as it will become alive again when entering a host. Alive in the sense that inside their host cells viruses observe the command "Crescite et multiplicamini" from the bible (grow and multiply), in the same way like any other living beings, even if they have to take control of various components of the host cell in order to do that.
I do not see any essential difference between a viral particle and a dormant seed or a bacterial or fungal spore or an encysted protozoan.
All such resistant forms of living beings have the purpose of remaining intact in environments where they cannot found the food or water or air that they need for a normal life. Viruses have the least demands from their environment, while the others may have greater requirements, e.g. the presence of small amounts of free oxygen and water in their environment, in order to not die permanently, but that is more like an imperfection in their current design, not an intrinsically necessary attribute.
Viruses cannot live without their hosts, but that is true for any obligate parasite. Humans can also not live independently, at least for now, but only together with many other living beings able to synthesize the substances that we cannot. Therefore it is hard to draw a line between alive and non alive based on the amount of dependencies on other living beings.
It certainly is more useful to include viruses in what is covered by the word "alive", because they are subjected to the same kind of evolution like the cellular living beings. Moreover in the same way like many kinds of cellular living beings have appeared by hybridization between cellular living beings with distinct genetic heritage, there are also plenty of cases where new species of cellular living beings have appeared by hybridization with viruses, i.e. by incorporating permanently in their genome some genetic material from a viral ancestor. This includes even humans (and all other vertebrates).
Therefore, if you draw a graph of the genetic relationships between cellular living beings, it is inextricably intermingled with the corresponding graph for viruses.
So I think that the most convenient way is to consider that the living beings are divided into cellular living beings and viruses.
Regardless of the word choice, biology must study both cellular living beings and viruses, anyway, because none of them can be understood in isolation from the others.
It's as the sibling post says: "alive vs not alive" and "same species vs different species" are just human concepts that we attempt to shoehorn biological reality into. There's nothing about biology itself that says that any given example should have a clear answer either way.
A viral particle outside its host can be considered dead, in the sense that it is inert and it does not have any metabolism, but it is not definitively dead, as it will become alive again when entering a host. Alive in the sense that inside their host cells viruses observe the command "Crescite et multiplicamini" from the bible (grow and multiply), in the same way like any other living beings, even if they have to take control of various components of the host cell in order to do that.
I do not see any essential difference between a viral particle and a dormant seed or a bacterial or fungal spore or an encysted protozoan.
All such resistant forms of living beings have the purpose of remaining intact in environments where they cannot found the food or water or air that they need for a normal life. Viruses have the least demands from their environment, while the others may have greater requirements, e.g. the presence of small amounts of free oxygen and water in their environment, in order to not die permanently, but that is more like an imperfection in their current design, not an intrinsically necessary attribute.
Viruses cannot live without their hosts, but that is true for any obligate parasite. Humans can also not live independently, at least for now, but only together with many other living beings able to synthesize the substances that we cannot. Therefore it is hard to draw a line between alive and non alive based on the amount of dependencies on other living beings.
It certainly is more useful to include viruses in what is covered by the word "alive", because they are subjected to the same kind of evolution like the cellular living beings. Moreover in the same way like many kinds of cellular living beings have appeared by hybridization between cellular living beings with distinct genetic heritage, there are also plenty of cases where new species of cellular living beings have appeared by hybridization with viruses, i.e. by incorporating permanently in their genome some genetic material from a viral ancestor. This includes even humans (and all other vertebrates).
Therefore, if you draw a graph of the genetic relationships between cellular living beings, it is inextricably intermingled with the corresponding graph for viruses.
So I think that the most convenient way is to consider that the living beings are divided into cellular living beings and viruses.
Regardless of the word choice, biology must study both cellular living beings and viruses, anyway, because none of them can be understood in isolation from the others.