Explain why a cell is a biosystem.

The cell is a biological system, as it is referred to the cellular level of organization. This judgment is fair, since the cell has all the properties that can define it as a living system of organization. In a living cell, metabolism and exchange of energy with the environment take place, it is characterized by reactions to external stimuli, it is capable of division, there is a development cycle. In all unicellular organisms, the cellular level coincides with the organismal level. For example, Infusoria-shoe.