What is a characteristic feature of a virus?

A characteristic feature of a virus is that it is an obligate intracellular parasite. This means that viruses cannot reproduce or carry out metabolic processes independently; they must invade the cells of a host organism to replicate and multiply. Once inside a host cell, a virus can hijack the cellular machinery to produce new viral particles, thereby propagating itself.

This dependence on a host for replication is a key distinction between viruses and living organisms, which can typically carry out all necessary life processes on their own. In contrast, organisms with complex cellular structures, such as bacteria or eukaryotic cells, are capable of independent metabolic activity. Additionally, viruses do not possess the ability to carry out photosynthesis, as they lack the necessary organelles or biochemical pathways to harness light energy. Thus, the notion of a virus being an obligate intracellular parasite highlights its unique nature and dependence on host cells for survival and reproduction.