What defines the basic unit of life within all living organisms?

The basic unit of life within all living organisms is the cell. Cells are the smallest structural and functional units capable of performing life processes. They can exist as independent organisms, such as bacteria and yeast, or as part of larger multicellular organisms, including plants and animals. Each cell contains essential components, such as DNA, ribosomes, and membranes, which allow it to carry out vital functions like metabolism, energy conversion, and reproduction.

In contrast, tissue is a group of similar cells that work together to perform a specific function, while an organ is a structure composed of two or more types of tissues functioning together to carry out particular tasks. An organism is a complete individual entity made up of various systems, organs, tissues, and cells. Thus, it is the cell that serves as the fundamental building block of all life forms, highlighting its importance in biological sciences.