Pathogenic microorganisms that need living cells to survive and reproduce are known as what?

The correct answer is that pathogenic microorganisms needing living cells to survive and reproduce are classified as viruses. Viruses are unique in that they cannot carry out metabolic processes on their own and require a host's living cells to replicate. Once inside a suitable host cell, they hijack the cell's machinery to produce more viral particles, resulting in infection and, in many cases, disease.

Bacteria, on the other hand, are single-celled organisms that have the capability to live and reproduce independently in various environments, including soil and water, and do not require a host to survive. Fungi, which include yeasts and molds, are also independent organisms that can thrive on a range of organic materials. Parasites, while they do require a host organism to live and often to reproduce, are more complex organisms that can include some protozoa and worms, but they are not classified as viruses. Thus, the unique dependency of viruses on living host cells for their life cycle distinguishes them in this context.