What is the basic unit of life?

The cell is often referred to as the basic unit of life because it is the smallest structural and functional unit that can carry out all the processes necessary for life. Cells have the ability to grow, reproduce, respond to stimuli, and maintain homeostasis, which are essential characteristics of living organisms. All living things, whether unicellular (like bacteria) or multicellular (like plants and animals), are composed of cells, highlighting their fundamental role in biology.

In contrast, organs and tissues are composed of multiple cells working together to perform specific functions. An organ, such as the heart or lungs, is a collection of different tissues organized to perform a particular task. Similarly, tissues consist of groups of similar cells that perform a common function but are not viable on their own without forming part of an organ. While an organism is the entire living entity made up of various systems and structures, it ultimately derives its life processes from the cellular level. This hierarchy illustrates why the cell is designated as the basic unit of life in biology.