Of the 6 or 7 criteria biologists usually use to define life, viruses often fall short. E.g. viruses do not have their own metabolism. Everyone has their own d

Of the 6 or 7 criteria biologists usually use to define life, viruses often fall short. E.g. viruses do not have their own metabolism. Everyone has their own definition though. I remember reading a novel where life was defined simply as heredity, mutation, and adaptation. The second definition makes more sense to me, and implicitly includes viruses.