+ Stem Cells

+ Objectives Describe the process of differentiation Define stem cells and explain their importance

+ From One Cell to Many Muticellular organisms produced via sexual reproduction begin life as a single cell Individual cells become specialized in form and function through process of differentiation Once cells of a certain type (i.e. nerve, muscle, skin etc.) have formed, the cells CANNOT develop into a different type of cell

+ Stem Cells and Development A fertilized egg and the first few cells in an embryo are able to form ANY kind of cell and tissue are called totipotent Pluripotent- Embryonic cells that can become any type of body cell Unspecialized cells that can develop into differentiated cells are called stem cells Stem cells are found in embryos and adults Multipotent- Adult stem cells that can produce many, but not ALL, types of differentiated cells

+ Stem Cells and Development

+ Frontiers in Stem Cell Research Scientists want to learn about signals that tell a cell to become either specialized (hair, muscle, skin etc) or multipotent (flexible in cell type) Possible Benefits: Repair or replacement of damaged cells/tissues (insert picture of regenerated ear) Controversial: Ethical issues of life and death, especially when dealing with humans (embryos are destroyed in the process)

+ Frontiers in Stem Cell Research

+ Ethical concerns lead many scientists to conduct research on other organisms such as frog and sea urchin embryos Another example of a model species : Planarians (Flatworms)

+ What are planaria? A type of flatworm belonging to the family Platyhelminthes (i.e. liver flukes, tape worms etc. )

+ Think-Pair-Discuss How does the type of reproduction (sexual or asexual) help different species survive?

+ Laboratory Procedures Groups of 3-4 Important: Sharps will be used (Scalpel and glass), handle with care!! The flat worms are sensitive to light and touch, please handle with care