Tiny infectious agents that can only multiply when they are inside a host are called what?

Tiny infectious agents that can only multiply when they are inside a host are called what?

• A. Virus
• B. Bacteria
• C. Fungus
• D. Microorganism

Answer: (A)

Viruses are tiny infectious agents that can only multiply inside a host cell. They are obligate intracellular parasites: outside a cell they’re just inert particles with genetic material wrapped in a protein coat. They lack the machinery to carry out metabolism or replicate on their own, so they hijack the host’s cellular systems to make new virus particles. This dependence on a living host to reproduce sets them apart from bacteria and fungi, which are cellular organisms capable of growth and replication independently. A broad term like microorganisms includes viruses, but it doesn’t specify this crucial trait, so it isn’t as precise. That’s why virus is the best fit for the description.

Viruses are tiny infectious agents that can only multiply inside a host cell. They are obligate intracellular parasites: outside a cell they’re just inert particles with genetic material wrapped in a protein coat. They lack the machinery to carry out metabolism or replicate on their own, so they hijack the host’s cellular systems to make new virus particles. This dependence on a living host to reproduce sets them apart from bacteria and fungi, which are cellular organisms capable of growth and replication independently. A broad term like microorganisms includes viruses, but it doesn’t specify this crucial trait, so it isn’t as precise. That’s why virus is the best fit for the description.