What is considered the basic unit of life?

The cell is recognized as the basic unit of life because it is the smallest structural and functional unit that can carry out the processes necessary for life. Every organism, from the simplest bacteria to complex multicellular organisms such as humans, is composed of one or more cells. Cells perform essential functions, including metabolism, energy production, and reproduction, which are fundamental to the maintenance of life.

Tissues, organs, and systems are higher levels of organization that are built from cells. Tissues are groups of similar cells that work together to perform a specific function, organs are made up of different tissues working in harmony to carry out complex functions, and systems consist of various organs functioning together for broader purposes. Thus, while they are crucial components of biological organization, they are not considered the fundamental unit of life in the way that the cell is.