As I said, you have to consider the system of parasite+host (plus any other supporting processes).
I think a lot of the confusion arises from people confusing objects with processes that unfold over time. You can’t ask if an object is alive by itself; you have to specify the time-dynamics of the system. Statements like ‘a bacterium is alive’ are problematic because a frozen bacterium in a block of ice is definitely not alive. Similarly, a virus that is dormant is most definitely not alive. But that same virus inside a living host cell is participating in a living process i.e. it’s part of a self-sustaining chain of non-equilibrium chemical reactions. This is why I specifically used the words ‘chemical process’.
So this is a definition for “life” only, not “living organism,” and you would say that a parasite, virus, or prion is part of something alive, and that as soon as you remove the parasite from the host it is not alive. How many of its own life functions must a parasite be able to perform once removed from the host in order for it to be considered alive after removal from the host?
How many of its own life functions must a parasite be able to perform once removed from the host in order for it to be considered alive after removal from the host?
As the definition says. It must demonstrate non-equilibrium chemistry and must be self-sustaining. Again, ‘simple forms of energy’ is relative, so I agree that there’s some fuzziness here. However, if you look at the extreme complexity of the chemical processes of life (dna, ribosomes, proteins, etc.) and compare that to what most life consumes (sugars, minerals, etc.) there is no ambiguity. It’s quite clear that there’s a difference.
As I said, you have to consider the system of parasite+host (plus any other supporting processes).
I think a lot of the confusion arises from people confusing objects with processes that unfold over time. You can’t ask if an object is alive by itself; you have to specify the time-dynamics of the system. Statements like ‘a bacterium is alive’ are problematic because a frozen bacterium in a block of ice is definitely not alive. Similarly, a virus that is dormant is most definitely not alive. But that same virus inside a living host cell is participating in a living process i.e. it’s part of a self-sustaining chain of non-equilibrium chemical reactions. This is why I specifically used the words ‘chemical process’.
So this is a definition for “life” only, not “living organism,” and you would say that a parasite, virus, or prion is part of something alive, and that as soon as you remove the parasite from the host it is not alive. How many of its own life functions must a parasite be able to perform once removed from the host in order for it to be considered alive after removal from the host?
Precisely.
As the definition says. It must demonstrate non-equilibrium chemistry and must be self-sustaining. Again, ‘simple forms of energy’ is relative, so I agree that there’s some fuzziness here. However, if you look at the extreme complexity of the chemical processes of life (dna, ribosomes, proteins, etc.) and compare that to what most life consumes (sugars, minerals, etc.) there is no ambiguity. It’s quite clear that there’s a difference.