In biology, there are no exhaustive criteria of living nature, and living organisms are characterized by a number of phenomenological features such as the ability to move, irritability, the ability to reproduction, adaptation to changing external environment, etc. However, these only are characteristics of a particular protein form of living nature that exists on Earth.
Therefore, I would suggest the following general definition of living nature.
Life is a structure participating in the emergence of a similar structure which cannot appear if an original structure has not existed.
Thus, the thesis - The meaning of life is in its very existence – is the main methodological principle of the study of living organisms.
Since a living structure is involved in the emergence of a similar structure, it should be inherently active, and the possibility of implementation of this activity reveals itself as freedom.
Therefore, freedom is an immanent property of living nature.