Living matter is subject to the laws which govern matter, and like matter of any other sort it is composed of atoms and molecules.

There is no force inherent in living matter, no vital force independent of and differing from the cosmic forces; the energy which living matter gives off is counterbalanced by the energy which it receives.

It undergoes constant change, and there is constant interchange with the environment.

The molecules which compose it are constantly undergoing change in their number, kind and arrangement.
Atom groups as decomposition products are constantly given off from it, and in return it receives from without other atom groups with which it regenerates its substance or increases in amount.

All definitions of life convey this idea of activity.