What is the basic unit of life?

The basic unit of life is the cell. Cells are the smallest structural and functional units of an organism, capable of performing all the necessary processes to sustain life. They can replicate, respond to stimuli, and carry out metabolic functions.

All living organisms, from the simplest bacteria to complex multicellular organisms like humans, are composed of cells. These cells can be specialized for various functions, forming tissues, which in turn make up organs, and ultimately systems. While tissues, organs, and systems are important components of biological organization, they are all built from cells, highlighting the integral role of the cell in the hierarchy of life. Cells can exist independently (as in unicellular organisms) or work together in multicellular organisms to maintain life, illustrating their fundamental nature in biology.