1. Unit 2 – Multicellular Organisms 2.2 Stem Cells and Meristems
National 5 Biology
Unit 2 – Multicellular Organisms
2.2 Stem Cells and Meristems

2. Learning Intentions
State that stem cells are non-specialised (undifferentiated) cells
State that stem cells can become any type of cell
State that stem cells are involved in growth and repair
Give examples of uses of stem cells in animals
State what is meant by a meristem
State that meristems are the only sites of cell division in plant cells
State that the cells produced in meristems are non-specialised (undifferentiated ) cells
State that cell division in meristems allows plants to grow.

3. Stem Cells Involved in growth and repair of organisms
Produce specialised cells in animals.
Have the ability to become any type of cells.

4. Types of Stem Cells Embryonic stem cells
- derived from embryos that develop from eggs fertilised in a laboratory.
Adult stem cells
Found in body along side other differentiated cells
Examples
- bone marrow
- blood vessels
- skin
- liver
- heart
They are body’s built-in repair kits
Replace cells damaged by disease, injury and every day wear and tear

5. Can develop into any cell [as in embryo]
Can develop into some cells

6. Source of stem cell
Medical Use
Marrow in bones
Treating leukaemia, a type of cancer caused by abnormal blood cells.
Skin
Growing new layers of skin that can be used to treat burn victims.
Heart muscle
Repairing damaged heart muscle after a heart attack (still being tested at the moment)
Bladder
Building a new bladder in the laboratory for a patient whose bladder has been damaged by injury or disease.

13. Complete the following table

14. Potential uses of stem cells

15. Meristems in plants Plants continue to grow throughout life
New cells are produced at meristems
This allows growth to take place
Tips of shoots and roots
Some unspecialised cells continue to divide
Others develop into specialised cells

16. What are meristems?
Meristems are the sites of production of non-specialised cells in plants.
These cells have the potential to become any type of plant cell and contribute to plant growth.
They are the only sites for cell division in a plant.

17. Where are meristems found in the plant?
Meristems are present at root and shoot tips (apical meristems) and lateral buds (lateral meristems)
Lateral buds

18. New cells expand by a process called elongation
Cells at root and shoot tips undergo rapid mitosis and cell division producing new cells
New cells expand by a process called elongation
New cells produced can differentiate to form specialised tissues such as xylem or phloem
Xylem and phloem
Differentiation
Elongation
Mitosis

19. Lateral meristems consist of cambium cells.
Xylem
Vascular Bundle
Cambium
Phloem
Lateral meristems consist of cambium cells.
These cells are situated in vascular bundles between xylem and phloem tissue

20. Secondary Thickening ( growth )
Xylem
Cambium
Phloem
Vascular Bundle

21. Xylem is produced every year leading to the formation of annual rings
Rings of Xylem
Year 3
Year 4
Xylem is produced every year leading to the formation of annual rings

22. Year 4 Cambium Year 3 Year 2 Year 1 Poor year Summer into autumn Xylem
Good year
Spring into summer Xylem
Year 1

23. Size of annual rings
Spring into Summer – large thin walled xylem vessels allow for increased flow of water and minerals.
Summer into Autumn – small thick walled xylem provide greater support.
The width of each ring is dependent upon growing conditions present during that year.
Wider rings are produced by warm or wet weather
Narrow rings are produced by cold or dry conditions.

24. Root Meristem Zone of specialisation Zone of elongation
Zone of cell division
Root hair

25. Shoot Meristem