Multi cellular organisms have different types of cells and each of these cells have different functions to perform. For e.g. red blood cells helps in the transport of oxygen, white blood cells help in protection of the body against pathogens, nerve cells for bodily co-ordination etc. A group of cells, which are of the same type, perform the same function like the cells of the kidney helping in excretion, the cells of the respiratory system helping in respiration, the cells in the digestive system helping in nutrition etc. Thus we can see that in multi cellular organisms each function is performed by each system, which exhibits division of labour.