What is the smallest unit of life capable of existing independently?

The smallest unit of life capable of existing independently is the cell. Cells are the basic building blocks of all living organisms and can carry out all processes necessary for life. They contain the necessary components to sustain themselves and can reproduce independently under suitable conditions.

Tissues, organs, and systems are larger biological structures that are comprised of multiple cells working together to perform specific functions. Tissues are groups of similar cells that perform a common function, organs are made up of different tissues working together, and systems are groups of organs that interact to carry out complex functions. However, these structures cannot exist independently as they rely on the cellular level for their existence. Thus, the cell stands as the fundamental unit that can function autonomously.