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.

2 Types of Cell Division 

These are of two types 

1. Mitosis or Mitotic Cell Division
2. Meiosis or Meiotic cell division

Mitosis or Mitotic Cell Division

• 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.

Also Check – 7 Important Difference Between Mitosis and Meiosis

Meiosis or Meiotic cell Division

• 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

1. Meiosis-I
2. Meiosis-II 

Meiosis-I

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

Meiosis-II 

• In contrast to meiosis-I, meiosis-II resembles a normal mitosis.

Why is there a need for New Cells ? Why Cell Division is Important ?

New cells need to be produced for 

1. Growth
2. Replacement
3. Repair and 
4. Reproduction

Growth

• 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.

Replacement

• 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.

Repair

• 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

• 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. 

Also Check – Is Meiosis part of the Cell Cycle?

Also Check – 12 Important Significance of Mitosis

Also Check – Cell Theory – Definition , History, Principles, Scientists

Also Check – What is Mitosis?