Life Processes 

We see the variety of things around us in which some are living and some are non living. All the living organisms have organized cellular structure with different levels of organization. An organized and ordered structure with cells, tissues, organs, organ system, is an important feature of living organism that distinguishes it from non living organisms. If this organization break down then the organism is no longer living. The maintenance functions of living organisms must go on forever to sustain life. The process which together performs this maintenance job are called life process. The life process needs energy, which mostly comes from the plants and trees. The outside source of energy is varied, as the environment is not in our control. So these sources of energy is needed to be broken down or built up inside our body. The process of taking in oxygen and using it for the purpose of breaking down food molecule inside our body for releasing energy is called respiration. Whether it is a multicellular or unicellular organisms, the energy is required by all.