By the end of this lesson
- Identify roles of mitosis in organisms.
- Link mitosis to growth and repair.
- Explain its role in asexual reproduction.
BIG QUESTION
Why does a scraped knee heal with matching skin rather than a new cell type?
Mitosis preserves a cell lineage’s genome, while gene expression maintains its specialised identity.
Growth increases cell number
Multicellular organisms grow mainly by repeated mitosisCell division that produces two genetically identical diploid cells, for growth, repair and asexual reproduction., increasing the number of cells. Cells may also enlarge and differentiate after division.
Mitosis occurs in growing regions such as plant meristemA region of a plant, such as a shoot or root tip, where cells divide by mitosis, allowing growth. and in developing animal tissues.
Repair replaces damaged or lost cells
stem cellAn unspecialised cell that can divide to renew itself and can differentiate into one or more types of specialised cell. and dividing tissue cells undergo mitosis to replace cells lost through normal wear, injury or programmed cell death.
The replacement cells inherit the same DNA sequence, helping tissues maintain their function.
Asexual reproduction makes clones
Single-celled organisms can reproduce by cell division. In plants, mitosis underlies vegetative propagation and tissue culture.
cloneAn organism or cell that is genetically identical to its parent; cloning is producing such copies. begin genetically identical, although mutations and environments can later create differences.
Uses of mitosis
The same division process serves different biological purposes.
| Context | What increases | Why identity matters |
|---|---|---|
| Embryonic growth | Cell number. | Builds tissues from one zygote. |
| Skin repair | Replacement cells. | Restores barrier function. |
| Bone-marrow renewal | Blood-cell precursors. | Maintains blood production. |
| Plant root tip | Meristem cells. | Extends root and forms tissues. |
| Vegetative propagation | Clone number. | Preserves successful genotype. |
Language that earns precision
- growth
- Permanent increase in size or cell number.
- repair
- Replacement or restoration of damaged tissue.
- stem cell
- Cell able to divide and produce specialised descendants.
- meristem
- Plant region containing actively dividing unspecialised cells.
Common misconceptions
Claim: Mitosis only happens in embryos.
Correction: It also supports repair, renewal and asexual reproduction.
Claim: Every adult body cell divides continually.
Correction: Division rate varies greatly between tissues and cell types.
Claim: A clone cannot differ from its parent.
Correction: Mutations and different environments can create differences after cloning.
Match the answer to the command word
Name mitosis and link it to cell-number increase.
Replacement cells inherit matching genetic information.
Recall, apply, then justify
Explain how mitosis supports wound healing.
Hint
Replacement, division and identical cells.
Suggested marking points
- Cells at or near the wound divide by mitosis.
- New cells replace damaged or lost cells.
- They are genetically identical to parent tissue cells and can restore tissue function.
State two uses of mitosis in plants.
Hint
Think growth, repair and cloning.
Suggested marking points
- Growth at meristems/root or shoot tips.
- Asexual/vegetative reproduction or tissue repair.
Explain why mitosis alone cannot produce a whole functional organ from any single adult cell without further controls.
Planning hint
Division versus differentiation, organisation and signals.
What a strong design includes
- Mitosis increases cell number and preserves DNA.
- A functional organ contains multiple specialised cell types.
- Cells need differential gene expression to specialise.
- Tissues require spatial organisation and signalling.
- Blood supply, extracellular matrix and connections may be required.
- Uncontrolled division can produce disorganised tissue or tumours rather than an organ.