What is the basic unit of all living things?

The cell is recognized as the basic unit of all living things because it is the smallest structural and functional unit capable of performing life processes. Cells are responsible for various vital functions, such as metabolism, growth, response to stimuli, and reproduction. All organisms, whether unicellular like bacteria or multicellular like humans, are composed of one or more cells, making the cell fundamental to the organization of life.

In the context of the other options, tissue is a group of cells that work together to perform a specific function, while an organ is a structure made up of different tissues that work together for a common purpose. An organism refers to an entire living entity, composed of multiple systems that include organs, tissues, and cells. These definitions highlight that cells are the foundational building blocks from which more complex biological structures are formed, underscoring their significance in the hierarchy of life.