What is the basic unit of life that performs all functions necessary for living organisms?

The basic unit of life that performs all functions necessary for living organisms is the cell. Cells are the smallest structural and functional units of an organism, and they are capable of carrying out all biological processes. Each cell can perform vital functions such as metabolism, energy production, and growth, as well as responding to environmental stimuli.

Cells can function independently in unicellular organisms, such as bacteria and protozoa, while in multicellular organisms, they work together to form tissues and organs, contributing to the organism's overall function and health.

While organs, tissues, and organ systems are composed of groups of cells and play crucial roles in the overall functioning of organisms, they are higher levels of organization that depend on the activities of individual cells to perform their specific roles within the body. Thus, the cell stands out as the fundamental unit that characterizes all forms of life.