An organism that lives off other living organisms is called a parasite.

Here's a breakdown:

* Parasite: An organism that lives in or on another organism (called the host) and benefits by deriving nutrients at the host's expense.

* Host: The organism that provides sustenance and shelter to the parasite.

There are many different types of parasites, including:

* Endoparasites: Live inside the host's body, like tapeworms or roundworms.

* Ectoparasites: Live on the surface of the host's body, like fleas, ticks, or lice.

* Obligate parasites: Need a host to survive and reproduce.

* Facultative parasites: Can survive independently but prefer to live as parasites.

Let me know if you have any more questions!