Cell proliferation describes the process by which cells grow and divide to produce daughter cells in multicellular organisms

• Cell proliferation allows for organismal growth, the replacement of dead cells and tissue repair 
  

Growth

The initial growth and development of a multicellular organism is mediated by the proliferation of undifferentiated pluripotent stem cells

• In animals, the rapid division of a zygote results in a mass of pluripotent stem cells (morula) that differentiate to form a blastocyst (early stage embryo)
  

• Plants retain pluripotent cells throughout their lifespan in specialised tissues called meristems
  

  • Apical meristems are responsible for primary growth and cause the lengthening of both shoots and roots 

  • Lateral meristems are responsible for secondary growth and cause the thickening of stems

Repair

Cell proliferation can also be used to replace cells at the end of their lifespan or regenerate tissues that have been damaged

• Red blood cells have a life expectancy of ~120 days, while the epidermal cells of the gut lining last for less than a week

• In animals, multipotent stem cells are stored within specific stem cell niches (e.g. bone marrow and hair follicles)

• These niches provide the chemical signals needed for the stem cells to differentiate into the types of tissues needed