Unit 2 – Multicellular Organisms 2.2 Stem Cells and Meristems 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 non-specialised (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. 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

Potential uses of stem cells http://www.eurostemcell.org/stem-cell-factsheets http://www.medicinenet.com/stem_cells/article.htmells/sctoday/ http://www.scribd.com/doc/104427724/types-of-stem-cells-and-their-current-uses http://learn.genetics.utah.edu/content/tech/stemcells/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 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.

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

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

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

Secondary Thickening ( growth ) Xylem Cambium Phloem Vascular Bundle

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

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

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.

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

Shoot Meristem www.speysidehigh.net/sites/default/.../Unit%202%20Web%20Part%20