What are the basic units of life?

The basic units of life are cells. Cells are often referred to as the building blocks of all living organisms because they are the smallest unit of structure and function in biological systems. Every organism, whether unicellular (like bacteria) or multicellular (like humans), is composed of cells.

Cells carry out essential life processes, including metabolism, energy conversion, and reproduction, demonstrating all characteristics of life. They contain the necessary components, such as organelles, that enable these processes to occur.

In contrast, tissues are groups of similar cells working together for a specific function, organs are structures comprised of multiple tissues performing complex functions, and systems are groups of organs that work together to accomplish broad physiological tasks. While all these structures are critical to the organization of living things, they are not the fundamental units of life; that distinction belongs to the cell.