Download Stem Cells and Meristems - Smithycroft Secondary School

National 5 Biology
Unit 2 – Multicellular Organisms
2.2 Stem Cells and
Meristems
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 nonspecialised (undifferentiated ) cells
• State that cell division in meristems allows plants to grow.
Stem Cells
• Involved in growth and repair of
organisms
• Produce specialised cells in animals.
• Have the ability to become any type of
cells.
http://outreach.mcb.harvard.edu/animations/thera7c.swf
Types of Stem Cells
• Embryonic stem cells
• - derived from embryos that develop from eggs fertilised
in a laboratory.
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•
•
•
•
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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
Can develop into any cell [as in embryo]
Can develop into some cells
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.
Complete the following table
Embryonic Stem cells
Pros
Cons
Adult Stem cells
Pros
Cons
Potential uses of stem cells
• http://www.eurostemcell.org/stem-cellfactsheets
• http://www.medicinenet.com/stem_cells/arti
cle.htmells/sctoday/
• http://www.scribd.com/doc/104427724/types
-of-stem-cells-and-their-current-uses
• http://learn.genetics.utah.edu/content/tech/s
temcells/sctoday/
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
What are meristems?
• Meristems are the sites of production of nonspecialised 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.
Where are meristems found in the plant?
• Meristems are present at root and shoot tips
(apical meristems) and lateral buds (lateral
meristems)
Lateral buds
• Cells at root and shoot tips
undergo rapid mitosis and
cell division producing
new cells
• New cells expand by a
process called elongationXylem and
• New cells produced can phloem
differentiate to form
specialised tissues such as
xylem or phloem
Differentiation
Elongation
Mitosis
Lateral
meristems
Vascular
Bundle
Xylem
Cambium
Phloem
• Lateral meristems consist of cambium cells.
• These cells are situated in vascular bundles
between xylem and phloem tissue
Secondary Thickening ( growth )
Xylem
Cambium
Phloem
Vascular Bundle
Year 1
Year 2
Rings of
Xylem
Year 3
Year 4
• Xylem is produced every year leading to the
formation of annual rings
Year 4
Poor year
Cambium
Year 3
Summer into autumn Xylem
Good year
Year 2
Spring into summer Xylem
Year 1
Size of annual rings
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•
•
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.
a. Wider rings are produced by warm or wet
weather
b. Narrow rings are produced by cold or dry
conditions.
Root Meristem
Zone of specialisation
Zone of elongation
Zone of cell division
Root hair
Shoot Meristem
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