Which term describes an organism that requires a host cell for survival and reproduction?

The term that describes an organism needing a host cell for survival and reproduction is "obligate intracellular parasite." This classification refers to organisms such as certain viruses, bacteria, and protozoa that cannot complete their life cycle or replicate without being inside a host cell. These parasites have evolved mechanisms to invade host cells and exploit the cellular machinery to replicate and produce offspring. Their dependency on host cells for nutrients, reproduction, and survival distinguishes them from free-living organisms, which can thrive independently in their environment, and from facultative parasites, which do not require a host for their entire lifecycle. Obligate anaerobes are microorganisms that thrive in environments devoid of oxygen, but their classification is based on their ecological niche rather than their dependence on a host for survival.