Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Cell division

Page:

  1. 1
  2. 2
  1. Next

There are two types of cell division. Mitosis is used for growth and repair and produces diploid cells identical to each other and the parent cell.

Meiosis is used for sexual reproduction and produces haploid cells different to each other and the parent cell.

Growth

Humans are made of millions of cells. This has a number of benefits:

  • cells can be specialised to do particular tasks
  • groups of cells can function as organs making a more efficient but complex organism
  • the organism can grow very large

Cell division

New cells are needed throughout life. These are for growth, to replace damaged cells and repair worn out tissues. Normal human body cells are diploid – they have two of each chromosome. When new cells are made, these 46 chromosomes (in other organisms the number is different) are copied exactly in a process called mitosis.

Mitosis

Mitosis is the type of cell division used for growth and repair. Mitosis occurs wherever new cells are needed. It produces two cells that are identical to each other, and the parent cell.

Higher tier only

In mitosis each chromosome is copied exactly. The new chromosomes are moved to opposite sides of the cell, before the cell divides leaving one complete set of 46 chromosomes in each of the two new cells.

Diagram of the stages of mitosis

Diagram of the stages of mitosis

Constant cell division ensures that cells never get too large. The larger the cell becomes, the smaller its surface area to volume ratio. Objects with a small surface area to volume ratio find it difficult to maintain exchange of materials with their environment. Large cells could run out of oxygen, and accumulate too much waste, such as carbon dioxide. For this reason it's more efficient for large organisms to be multicellular, rather than single-celled.

Page:

  1. 1
  2. 2
  1. Next

Back to Living and growing index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.