All living things have something in common- The CELL. Right from a simple bacteria to human beings each of them is made up of cells. Some are Unicellular i.e; made up of single cell and some are multicellular i.e; made up of many cells. It is the smallest subunit or building block of a living organism.
All the key process like Respiration, Digestion, Replication takes place in the cell. The cell has a semi permeable membrane which facilitates the transport of materials to and fro. The cell contains DNA which is the basis hereditary unit of life. The cell in turn gives rise to tissues which further give rise to the Organs and ultimately the Organ System.
Just as we see buildings, bungalows and towers constructed look different from each other in terms of shape, size but all of them have one thing is common that is the Building Block used to construct them.
The common basic, structural and functional unit of living beings is called a Cell.