What is division of labour? Explain it in context of multicellular organisms.

In multicellular organisms, Cells become specialised to perform different functions. Similar cells group together to form tissue for eg. muscular tissue. Tissues organised to form organs such as heart, kidney and then organ organise into organ system (Circulatory system, excretory system, digestive system, etc.) to perform major functions. Thus, a living organism has a number of organ systems. This is known as division of labour in multicellular organisms.