Final answer:
A facultative parasite can live on its own or as a parasite when a host is present, benefiting from the host's resources without killing it immediately to ensure the continuation of its reproductive cycle.
Step-by-step explanation:
A parasite that can live independently or may live as a parasite when a host is available is known as a facultative parasite. This type of organism can exist either as a free-living individual or take on a parasitic lifestyle when the opportunity arises, benefiting from the resources of a host. Facultative parasites are contrasted with obligate parasites, which must live as parasites because they cannot survive in a free-living state.
Parasitism is a biological relationship where the parasite species lives in or on another species, the host, and causes harm to the host while deriving benefits for itself. Parasites may live either inside (as endoparasites) or on the surface (as ectoparasites) of their host. While most parasites do not immediately kill their host to ensure the completion of their reproductive cycle, they do weaken the host by siphoning essential nutrients.