Growth

• what happens when an organism produces new cells?

  it increases its cell number and can grow, repair tissue and replace dead cells
• how are cells produced in plant and animal embryos?

  they are produced by mitosis, so that they are all genetically identical
• what happens to tissue in adult mammals?

  some tissues are constantly worn away, such as the skin and the gut lining
• what are examples of tissues in adult mammals that constantly get worn away?

  • skin
  • the gut lining
• how do the tissue in adult mammals that constantly get worn away get replaced?

  identical cells replace them by mitosis
• where does mitosis continuously occur in mammals?

  • in bone marrow - producing red and white blood cells
  • in the nail beds and hair follicles
• where does mitosis occur in plants?

  mitosis occurs in plants in small groups of cells, in the root and shoot apex, called meristems
• why do plants grow by cell expansion and not cell division?

  • the meristematic cells in the root apex and the shoot apex remain very small
  • mitosis increases the number of cells in a plant, but for a plant to grow, cell expansion must occur