What is the basic unit of life?

The basic unit of life is the cell. Cells are the smallest structural and functional units of living organisms. They form the building blocks of all life forms, ranging from single-celled organisms like bacteria to complex multicellular organisms such as plants and animals. Each cell carries out essential functions necessary for the organism's survival, such as metabolism, energy production, and the response to stimuli.

Tissues, organs, and organisms are made up of groups of cells. Tissues are collections of similar cells that perform a specific function, organs are structures composed of different tissues working together for a common purpose, and organisms are complete living entities made up of various organ systems. Thus, while these other options are important components of biological organization, they rely on the existence and function of cells to operate effectively.