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Multicellular organisms are made up of millions and trillions of cells. All these cells perform specific functions. All the cells specialised for performing similar functions are grouped together as tissues in the body. Hence, a particular function is carried out by a group of cells at a definite place in the body. Similarly, different functions are carried out by different groups of cells in an organism. This is known as division of labour in multicellular organisms.
In a unicellular organism, a single cell is responsible for all the life processes. This is called cellular level of organization. This can be seen in some simple multicellular organisms as well. But in most of the multicellular organism, there are different groups of cells to carry different functions. Thus, formation of tissues paves the way for division of labour in multicellular organisms.
In Multicellular organisms, different group of cells perform different tasks in sustaining an ‘organism- Each group of cells perform a well defined task which is different from others but interact and co-operate with other cells. For eg: conduction by nerve cells, secretion by gland cells, red blood and white blood cells found in the blood etc. Thus multicellular organisms exhibit division of labour.