What is Cell Division?

Cell division is a process of formation of new cells from the pre-existing cells.

New cells are formed in an organism in order to grow, replace cells (old, dead, injured) and form gametes during sexual reproduction.

Table of Contents

2 Types of Cell Division

These are of two types

This occurs for growth of organisms and to replace old, dead or injured cells.
The dividing cells are called mother cells which form two identical daughter cells.
Each daughter cell has the same chromosome number as that of the mother cell.

This occurs in the sex organs of sexually reproducing cells.
The gametes are formed by this kind of cell division.
The male and female gamete unite to form zygote after fertilization give rise to offspring.
When a cell divides by meiosis, it produces four new cells instead of just two.

The process of meiosis occurs in two stages

In meiosis-I, the germ cells divide into two daughter cells which have only half number of chromosomes in comparison to mother germ cells.

New cells need to be produced for

Most organisms, including plants and animals, begin their life as a single cell (the fertilized egg).
This cell divides repeatedly to form a cluster of cells which start shaping for different functions to form tissues and organs.
Thus, cell division is essential for growth.

There is always a wear and tear of cells during the normal body functions. For example, 2 million red blood cells in our body are destroyed every second. These are replaced by new cells formed through a division of their parent cells in the bone marrow.
In plants, the old and dried leaves fall off and new ones grow out.

Apart from normal wear and tear of the tissues in the body, there may be accidental injuries. One may get cuts in the skin or fractures in the bone.
Repair of such injuries is again through cells which divide, cover up the gaps and join the broken ends.

Reproduction also takes place through the activity of the dividing cells. Amoeba or bacteria just divide to produce two similar independent cells by mitosis.
In higher forms, as in humans, or in the banyan tree, special cells in the reproductive organs undergo a special kind of cell division (meiosis) to produce sperms and eggs.
The sperms and eggs receive only half the number of chromosomes of their parent cells, i.e., one chromosome from each pair.