Cell is the structural and functional unit of life.
Explanation:
The organisms are classified on the different characteristics basis on the similarities and differences among the organisms. On the cellular basis two main types of organism are unicellular organism and multi cellular organism.
The cell theory of the life was given by Schleiden and Schwann. The cell acts as the basic unit of life as all living organisms are made of the cell. The cell combine together to form tissue, tissue to form organs and organ system as given in the example of the cat.
The first and major characteristic of life is a cellular organization out of eight major characteristic features of life every living organism possesses. It says that living things are made of cells. The cellular organization is the fundamental base of the growth and evolution of life.
The evolution of life includes the organization of the micromolecules to the macromolecules that form cell organelles and organelles to a cell, cells form tissue and tissues to organ and organ to organ system and ultimately this complex organization forms the whole organism such as cat.
Thus, the correct answer is - cellular organization.
