OCR A Level Biology:复习笔记2.6.4 The Significance of Mitosis

Significance of Mitosis

  • Mitosis is the process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent nucleus
  • The process of mitosis is of great biological significance and is fundamental to many biological processes:

Growth of multicellular organisms

  • The two daughter cells produced are genetically identical to one another (clones) and have the same number of chromosomes as the parent cell
  • This enables unicellular zygotes (as the zygote divides by mitosis) to grow into multicellular organisms
  • Growth may occur across the whole body of the organism or be confined to certain regions, such as in the meristems (growing points) of plants

Replacement of cells & repair of tissues

  • Damaged tissues can be repaired by mitosis followed by cell division
  • As cells are constantly dying they need to be continually replaced by genetically identical cells
  • In humans, for example, cell replacement occurs particularly rapidly in the skin and the lining of the gut
  • Some animals can regenerate body parts, for example, zebrafish can regenerate fins and axolotls regenerate legs and their tail amongst other parts

Asexual reproduction

  • Asexual reproduction is the production of new individuals of a species by a single parent organism – the offspring are genetically identical to the parent
  • For unicellular organisms such as Amoeba, cell division results in the reproduction of a genetically identical offspring
  • For multicellular organisms, new individuals grow from the parent organism (by cell division) and then detach (‘bud off’) from the parent in different ways
  • This type of reproduction can be observed in different plant, fungi and animal species
  • Some examples of these are budding in Hydra and yeast and runners from strawberries