What principle states that all living organisms are made of cells?

The principle that states all living organisms are made of cells is known as cell theory. This foundational concept in biology encompasses three main ideas: all living things are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells. This theory highlights the significance of cells in the structure and function of all living organisms, establishing cells as the fundamental building blocks of life.

Cell theory is essential because it provides a unifying framework for understanding biology and the organizational complexity of living things. It signifies that the cell is not just a basic unit but the primary unit that integrates into more complex structures, contributing to various biological functions. This understanding is crucial for those pursuing veterinary science and studying the biology of animals and their health.

The incorrect options refer to related concepts that do not encapsulate the principles stated in cell theory. For instance, the 'cell hypothesis' and 'cell function theory' do not accurately describe the holistic view of cellular composition in living organisms, while 'cell structure principle' fails to adequately convey the core tenets of life as documented in cell theory. Understanding this distinction is vital for grasping how life is organized at a cellular level.