Which term refers to the basic unit of life?

The term that refers to the basic unit of life is "cell." Cells are the smallest structural and functional units of living organisms, and they perform essential life processes. All living things are composed of one or more cells, making them the fundamental building blocks of life.

While tissue and organ are important components of biological organization, they are higher levels of complexity, consisting of groups of cells that function together (tissue) and arrangements of different tissues working collaboratively (organ). A membrane, on the other hand, refers to a structural layer surrounding and protecting cells, but it does not represent a unit of life by itself. The concept of the cell as the basic unit of life is a fundamental principle in biology, encapsulated in the cell theory, which states that all organisms are made of cells, and all cells arise from pre-existing cells.