What term refers to organisms that grow, feed, and shelter on or inside another organism?

The term that refers to organisms that grow, feed, and shelter on or inside another organism is "parasites." Parasites have a unique relationship with their hosts; they rely on the host for nutrients and protection while often causing harm to the host in the process. This phenomenon can be seen in various forms, such as tapeworms in the intestines of animals or ticks that feed on the blood of mammals.

Other options include bacteria, which are single-celled organisms that can exist independently and can be either beneficial or harmful; viruses, which require a host cell to replicate and cannot grow or feed on their own; and fungi, which can be decomposers or sometimes pathogenic. While fungi can also form symbiotic relationships (such as mycorrhizae with plants), they do not typically fit the definition of organisms that actively harm their hosts while feeding on them, as is characteristic of parasites. This distinction helps clarify why the correct term in this context is specifically "parasites."