Which of the following statements is NOT a part of the cell theory?

The statement regarding plants and animals being composed of different cell types is not considered part of the cell theory. The core principles of cell theory focus on three key ideas: that all living organisms are made of cells, that cells are the fundamental units of life, and that all cells arise from pre-existing cells.

The notion that plants and animals have different cell types is more about the diversity and specialization of cells within the two distinct categories of life rather than a foundational principle of cell theory itself. While it is true that there are various types of cells, such as plant cells and animal cells, this does not impact the fundamental tenets of cell theory, which apply universally across all living organisms.