Level: JHS, Basic 8 | Subject: Integrated Science | Strand: Diversity of Matter | Topic: Living Cells
Curriculum reference: B8.1.2.1 Demonstrate understanding of cell division (mitosis and meiosis). Indicator B8.1.2.1.1: Describe the process and importance of cell division. All the exemplars are merged into one set of notes.
1. What is Cell Division?
- Cell division is the process by which one cell divides to form new cells.
- Before a cell divides, its chromosomes are copied. Chromosomes are thread-like structures in the nucleus. They carry the genes that pass on features from parents to children.
- There are two types of cell division: mitosis and meiosis.
2. Mitosis
- Mitosis happens in body cells such as skin, bone, muscle and root tip cells.
- One parent cell divides once to give two identical daughter cells.
- Each daughter cell has the same number of chromosomes as the parent cell. In humans, this is 46.
Stages of mitosis
| Stage | What happens |
|---|---|
| Prophase | Chromosomes become short and thick and can be seen. The nuclear membrane breaks down. |
| Metaphase | Chromosomes line up at the middle (equator) of the cell. |
| Anaphase | Copies of each chromosome are pulled apart to opposite ends of the cell. |
| Telophase | Two new nuclei form. The cell splits into two daughter cells. |
Memory aid: PMAT (Prophase, Metaphase, Anaphase, Telophase). Pupils can see these stages in charts, diagrams, videos or under a microscope using onion root tips.
3. Meiosis
- Meiosis happens only in the sex organs (testes and ovaries) to make sex cells (gametes): sperm cells and egg cells.
- One parent cell divides twice to give four cells, each with half the number of chromosomes (23 in humans).
- The four cells are not identical to each other or to the parent cell.
- At fertilisation, a sperm (23) joins an egg (23) to make a zygote with 46 chromosomes. This keeps the chromosome number the same from one generation to the next.
4. Differences between Mitosis and Meiosis
| Point | Mitosis | Meiosis |
|---|---|---|
| Where it happens | Body cells | Sex organs |
| Number of divisions | One | Two |
| Cells produced | Two | Four |
| Chromosome number | Stays the same (46) | Halved (23) |
| Daughter cells | Identical | Different |
| Purpose | Growth, repair, replacement | Making sex cells for reproduction |
5. Importance of Cell Division
- Growth: a baby grows into an adult, and a seedling into a tree, because cells keep dividing by mitosis.
- Repair: a wound heals when new cells replace damaged ones.
- Replacement: old skin and blood cells are replaced.
- Reproduction: meiosis makes the sex cells needed for new life.
Remember: Mitosis gives two identical cells for growth and repair. Meiosis gives four sex cells with half the chromosomes for reproduction.
Ready to practise?
Education Always (education.inspiringalways.com). Original notes written to follow the NaCCA Basic 8 Integrated Science curriculum.