Which term best describes the basic unit of life?

• A. Cell
• B. Organ
• C. Tissue
• D. Organ System

Answer: (A)

Cells are the basic unit of life. They are the smallest units that can carry out all life processes, like getting and using energy, growing, responding to the environment, and reproducing. This idea comes from the cell theory: all living things are made of cells, and new cells come from existing cells. In multicellular organisms, cells with similar jobs form tissues, tissues build organs, and organs work together in organ systems. So a cell best fits the description because it is the smallest structure capable of carrying out life processes, either on its own in single-celled organisms or as part of larger, more complex organisms.