Every living body is a cell or cells. Life of every organism starts with a single cell. In fact, every cell is originated from a pre-existing one. The increase of cells in number through division is a very natural and important feature. The body of some organism is composed of a single cell. They are called unicellular organisms, such as bacteria, amoebas, plasmodium etc. These organisms multiply themselves from the division of a single cell. Other organisms are composed of more than one cell. They are called multicellular organisms. Humans, mango and Banyan trees etc. are composed of crores of cells. A giant Banyan tree also initiates its structure after the formation of a single cell (zygote by the union of two gametes). After the fertilization of an egg, the structure of a man is accomplish with the crores of cells dividing through the process of cell division. Again, male and female gametes are produced for the emergence of new generations. Cells divide through the process of cell division for the growth and reproduction of organisms

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