What is the basic unit of life?

The basic unit of life is the cell, which is the smallest structural and functional unit in all living organisms. Cells are often referred to as the "building blocks" of life because they perform essential functions such as metabolism, growth, and reproduction. Each cell can carry out the processes necessary to sustain life, including energy production, waste elimination, and response to stimuli.

Cells can exist independently, as in unicellular organisms like bacteria and yeast, or can form complex multicellular organisms, such as plants and animals, where different types of cells work together to perform specialized functions. Understanding that the cell is the fundamental unit of life is crucial in biology because it underpins concepts in areas ranging from physiology to genetics and ecology. Other options like atoms, tissues, and organs represent different levels of biological organization, but they are not independently capable of life on their own.