Question

how do viruses show characteristics of life even when they lack any membrane​

Answer 1

Viruses are made necleoprotein entities i.e the areade up of proteins called Capsid and nucleic acid either RNA or DNA. Outside the cell they are inert and crystallized in form. But once they enter into a host body, they start using host's machinery to replicate themselves. Thus they are considered be on the bordline of living and non-living organisms.

Answer 2

Viruses did not find a place in classification since they are not truly 'living'. Normally, we understand living as those organisms that have a cell structure. The viruses are non-cellular organisms that are characterised by having an inert crystalline structure outside the living cell. Once they infect a cell they take over the machinery of the host cell to replicate themselves, killing the host.