Life Processes

The maintenance function of living organisms must go on even when they are not doing anything particular. Even we are just sitting in home, even if we are just asleep, this maintenance job has to go on. The processes which together perform this maintenance job are life processes.
Since these maintenance processes are needed to prevent damage and break-down, energy is needed for them. This energy comes from outside of the body of the individual organism, which we call food, to the inside, a process we commonly call nutrition. If the body size of the organisms is to grow, additional raw material will also be needed from outside. Since life on earth depends on carbon-based molecules, most of these foods sources are also carbon-based. Depending on the complexity of these carbon sources, different organisms can then use different kinds of nutritional processes.