What term refers to an organism that is made up of multiple cells?

The term that refers to an organism made up of multiple cells is "multicellular." Multicellular organisms are characterized by having a complex structure consisting of many cells that work together to perform various functions. These cells can specialize in different tasks, contributing to the overall efficiency and survival of the organism. Examples of multicellular organisms include humans, trees, and animals, all of which have specialized cells that form tissues, organs, and systems.

In contrast, the term "unicellular" describes organisms composed of a single cell, such as bacteria and yeast. Prokaryotic organisms are defined by their cellular structure, lacking a nucleus and membrane-bound organelles, which includes unicellular organisms like bacteria. Eukaryotic organisms, on the other hand, have cells with a nucleus and membrane-bound organelles; they can be unicellular or multicellular. Thus, while some eukaryotic organisms are unicellular, multicellular specifically indicates the presence of multiple cells within the organism.