# The Significance of Mitosis ## Why Mitosis Matters - Mitosis produces two genetically identical daughter nuclei - The daughter nuclei are also genetically identical to the parent cell nucleus - They have the same number of chromosomes as the parent cell - This process is fundamental to three major biological processes: - Growth of multicellular organisms - Replacement of cells and repair of tissues - Asexual reproduction

Mitosis is nuclear division that produces two genetically identical daughter nuclei with the same chromosome number as the parent cell

## Growth of Multicellular Organisms - The two daughter cells produced are genetically identical to one another (clones) - Both daughter cells have the same number of chromosomes as the parent cell - This enables single-celled zygotes to grow into complex multicellular organisms through repeated mitotic divisions - Growth patterns vary depending on the organism: - Some organisms grow throughout their entire body - Others restrict growth to specific regions, such as meristems in plants

A zygote divides by mitosis repeatedly, with each division producing identical cells that eventually differentiate

### Example: From One Cell to Trillions - A fertilised human egg (zygote) contains just one cell - Through mitosis, this single cell becomes approximately 37 trillion cells in an adult human - Each cell retains the same genetic information as the original zygote - Think of it like photocopying a document - the original and all copies contain identical information ## Replacement of Cells & Repair of Tissues - Damaged tissues can be repaired through mitosis followed by cell division - Cells are constantly dying throughout the body - Dead or damaged cells need to be continually replaced by genetically identical cells - This ensures tissues maintain their structure and function ### High-Turnover Tissues - Some tissues require particularly rapid cell replacement: - Skin cells - the outer layer is constantly being shed and replaced - Intestinal lining - exposed to harsh digestive conditions and must be renewed frequently - In humans, the skin completely renews itself approximately every 2-4 weeks - The gut lining can renew itself in as little as 3-5 days ### Regeneration in Animals - Some organisms have remarkable regenerative abilities: - Starfish can regenerate lost arms through mitotic division - Salamanders can regrow entire limbs, including bone, muscle and nerve tissue - Flatworms can regenerate their entire body from small fragments - This regeneration relies on mitosis to produce new cells that replace lost structures

Without mitosis for cell replacement, organisms would quickly accumulate damaged cells and tissues would fail

## 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 - Mitosis is the mechanism that allows this to occur ### Unicellular Organisms - For single-celled organisms like bacteria, cell division directly results in reproduction - Each division of the parent cell produces a genetically identical offspring - This allows rapid population growth when conditions are favourable - Example: A bacterium can divide every 20 minutes under optimal conditions ### Multicellular Organisms - New individuals grow from the parent organism through mitotic cell division - The offspring eventually detach from the parent in various ways - This type of reproduction is observed in different species across kingdoms

Asexual reproduction produces clones - offspring that are genetically identical to the parent organism

### Examples Across Different Groups | Organism Type | Example | Method | |---------------|---------|--------| | Fungi | Baker's yeast | Budding - small outgrowth forms and separates | | Animals | Sea anemones | Budding - miniature organism grows from parent's side | | Plants | Spider plants | Runners - horizontal stems produce new plants at nodes | ### Advantages of Asexual Reproduction - No need to find a mate - Rapid population growth possible - Successful genetic combinations are preserved - Colonisation of new areas can occur from a single individual ### Disadvantages of Asexual Reproduction - No genetic variation in offspring - Entire population vulnerable to same diseases or environmental changes - Cannot adapt quickly to changing conditions - Harmful mutations are passed directly to all offspring