Compare the specialization of an unicellular organisms to that of a cell from a multicellular organism.

Unicellular organisms have only one cell in which all seven life processes take place.
These unicellular organisms are self-sufficient. They do not need  outside help to function. The multi-cellular organism has to rely on other cells to survive. So, the difference between the cells is that the cells from a multi-cellular organism are interconnected to each other and work together.

Where’s the selection?