Life Processes

The life processes need to do:

(i) To provide food that provides energy and material required to sustain life. The process is called nutrition.
(ii) Respiration to supply oxygen to break down food (especially glucose) in the cells of organisms to release energy.
(iii) Transportation process for carrying food and oxygen from one place to another in the body. Also to transport wastes from body cells to excretory tissues.
(iv) Excretion process that removes the by-products produced during other life processes and carried to excretory tissues.

A single-celled organisms does not need specific organs for taking in food, exchange of gases or removal of wastes because the entire surface of the organism is in contact with the environment. Thus tha exchange of gases can take place by simple diffusion and there is no need of special organs.

In multicellular organisms like us, all the body cells are not in direct contact with the surrounding environment. Thus, every cell of the body will not get oxygen as per need by the process of diffusion from the environment. So, complex multicellular organisms need a specialised tissues, organs and organ system to take in oxygen.

Some movements either visible like locomotion from one place to another and growth related movements or invisible movement such as movement of molecules are the criteria whether something is alive.