What is the difference between a one-celled organism and a single cell of a multicelled organism?
To explain: The difference between a single-celled organism and a single cell of a multi-celled organism.
The smallest basic functional unit of life is a cell. Some organisms consist of single cells, which complete all body functioning within one cell. Some organisms consist of multiple cells. They have specific cells for specific functioning. Some cells live and reproduce independently. Others do so as part of a multi-celled organism.