Here's why:

* Multicellularity: Multicellular organisms are made up of many different cells that work together. To perform all the necessary functions for life, these cells specialize in specific roles.

* Division of Labor: Specialized cells allow for a division of labor, with each cell type contributing to the overall function of the organism. This leads to increased efficiency and complexity.

* Examples: Examples of specialized cells include muscle cells for movement, nerve cells for communication, and blood cells for transporting oxygen.

Single-celled organisms (like bacteria and amoeba) are not made up of specialized cells. They perform all necessary functions within a single cell.