Which statement is part of the cell theory?

The statement that cells are the smallest units of life is a fundamental principle of cell theory, which asserts that all living organisms are composed of cells and that cells are the basic structural and functional units of life. This means that every biological process occurs within cells, and the characteristics of life can be attributed to cellular activity.

Cell theory is built upon key concepts established by scientists like Schleiden and Schwann, who emphasized that all living things are made up of one or more cells and that the cell is the basic unit of life. This understanding has been foundational in biology, shaping how we study and understand living organisms and their functions.

In contrast, the other statements do not align with established principles of biology: cells cannot arise from non-living matter, not all cells share identical structures as they can vary greatly between different organisms and cell types, and while organelles are components within cells, stating that all life forms are made of organelles misrepresents the concept that all life forms are fundamentally made of cells.