2. Richard Dawkins in which he presents an explanation of, and argument for, the theory of evolution by means of natural selection.
In his choice of the title for this book, Dawkins refers to thewatchmaker analogy made famous by William Paley in his book Natural Theology. Paley, arguing more than fifty years before Charles Darwin published On the Origin of Species, held that the complexity of living organisms was evidence of the existence of a divine creator by drawing a parallel with the way in which the existence of a watch compels belief in an intelligent watchmaker. Dawkins, in contrasting the differences between human design and its potential for planning with the workings of natural selection, therefore dubbed evolutionary processes as analogous to a blind watchmaker.

3. Stem Cells
A cluster of nascent retinae generated from 3D embryonic stem cell cultures, by UCL News on Flickr (CC):

5. A Stem Cell Story http://www.youtube.com/watch?v=2-3J6JGN-_Y
We will watch next class….
A Stem Cell Story

6. Stem Cells retain the capacity to divide and can differentiate along divergent pathways.
Totipotent
Can differentiate into any type of cell.
Pluripotent
Can differentiate into many
types of cell.
Multipotent
Can differentiate into a few closely-related types of cell.
Unipotent
Can regenerate but can only differentiate into their associated cell type
(e.g. liver stem cells can only make liver cells).
Image from:

7. Stem Cells retain the capacity to divide and can differentiate along divergent pathways.
By Fwfu at en.wikibooks [Public domain], from Wikimedia Commons

8. Stem Cells retain the capacity to divide and can differentiate along divergent pathways.
Screenshot from this excellent tutorial:

9. Key Concept: Structure vs Function
Differentiation (specialization) of cells:
All diploid (body) cells have the same chromosomes.
So they carry all the same genes and alleles. BUT
Not all genes are expressed (activated) in all cells.
The cell receives a signal.
This signal activates or deactivates genes.
Genes are expressed accordingly and the cell is committed.
Eventually the cell has become specialized to a function.
Key Concept: Structure vs Function
How do the structures of specialized cells reflect their functions? How does differentiation lead to this?
Screenshot from this excellent tutorial:

10. Treatment for Leukemia
Therapeutic Uses of Stem Cells
Treatment for Leukemia
Problem
Cancer of the blood or bone marrow, resulting in abnormally high levels of poorly-functioning white blood cells.
Treatment
Chemotherapy and radiotherapy can be used to destroy the white blood cells, but these need to be replaced with healthy cells. Bone marrow transplants are often used for this.
Role of Stem Cells
Hematopoetic Stem Cells (HSCs) can be harvested from bone marrow, peripheral blood or umbilical cord blood. As these can differentiate to form any type of white blood cell, they can be used to repopulate the bone marrow and produce new, healthy blood cells. The use of a patient’s own HSCs means there is far less risk of immune rejection than with a traditional bone marrow transplant.
From:
Animation of this process:
Animated tutorials from:

11. Uses of Stem Cells
Stargardt’s disease: Early vision loss usually leading to blindness due to a gene mutation
Retinal pigment epithelial stem cells can be used to regenerate and support function of the eye’s light sensitive cells that have been damaged

12. Two Minute Essay What is a stem cell?
How do stem cells differentiate into specialized cells?
Outline one therapeutic use of stem cells.
Free images from: Presentations ETC, University of Florida.

13. Ethics of Stem Cells Specially created embryos Umbilical cord blood
is it right to create embryos just for medical use?
what about the ones that do not get used?
when do we say “life” begins?
Umbilical cord blood
Adult’s own tissues

15. Assignment for today
STEM CELLS

16. Objective 1.2 Ultrastructure of cells
Understanding (Statement objectives)
Prokaryotes have a simple cell structure without compartments.
Eukaryotes have a compartmentalized cell structure.
Prokaryotes divide by binary fission.
Electron microscopes have a much higher resolution than light microscopes.
Applications
Describe the structure and function of organelles within exocrine gland cells of the pancreas.
Describe the structure and function of the organelles within palisade mesophyll of the leaf.
Nature of science
Developments in scientific research follow improvements in apparatus: Describe how the invention of electron microscopes led to greater understanding of cell structure.
Skills
Draw and label a diagram of the ultrastructure of prokaryotic cells based on electron micrographs.
Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
Draw and label a diagram of the ultrastructure of eukaryotic cells based on electron micrographs.
Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S ribosomes and a nucleus, mitochondria and other membrane-bound organelles are present in the cytoplasm. Some eukaryotic cells have a cell wall.
Interpret of electron micrographs to identify organelles and deduce the function of specialized cells.
Compare eukaryotic and prokaryotic cells.
Naked DNA versus DNA associated with proteins
DNA in cytoplasm versus DNA enclosed in a nuclear envelope
No mitochondria versus mitochondria
70S versus 80S ribosomes
Eukaryotic cells have internal membranes that compartmentalize their functions.
State three differences between plant and animal cells.

17. Prokaryotes
Image: Hospital-associated MRSA by NIAID on Flickr

18. Prokaryotes “Before nucleus:” evolutionary precursors to eukaryotes.
Escherichia coli (E. coli)

19. Prokaryotic Cell Parts
mesosome
cell wall
plasma membrane
pili
cytoplasm
nucleoid
ribosomes
flagella
Prokaryotic cell parts are not generally membrane-bound, so we don’t refer to them as organelles.
Cell structures animation:

20. Prokaryotic Cell Parts
mesosome
cell wall: protective protein-based coating (Gram + / Gram -)
plasma membrane: selectively permeable, controls entry & exit of materials to and from the cell.
pili: attach to other bacteria for DNA transfer
cytoplasm: contains enzymes for metabolic reactions
nucleoid: closed-loop of bacterial DNA in a condensed area
ribosomes: protein synthesis (transcription & translation)
flagella: whiplash-like motion causes movement
Cell structures animation:

21. Prokaryotic Cell Parts
mesosomes
These don’t really exist naturally as bacterial cell parts, and could be an example of a paradigm shift in thinking.
They were observed in some electron micrographs and thought to be in-folds of membrane used for division, respiration or making cell walls…
… turns out they are an
artifact of the
preparation method
for some electron
microscope images.
Cell structures animation:

22. Past-paper question: E. coli TEM image
Identify these structures: I.
II.
III.
IV.
Calculate the magnification of the image.
Image from IB Biology QuestionBank CDRom – get a copy here:

23. Past-paper question: E. coli TEM image
Identify these structures:
I. Plasma membrane
II. Cell wall / pili
III. Nucleoid
IV. Cytoplasm / ribosomes
Calculate the magnification of the image. 1. Measure the scale bar in mm.
2. Multiply x 1000 to convert to μm.
That is the magnification.
How long is the bacterium?
Image from IB Biology QuestionBank CDRom – get a copy here:

24. PROKARYOTES E P R O D U C
through
binary fission
two-parts
splitting

25. binary fission PROKARYOTES E through P R O D U C
The closed-loop DNA of the bacterium makes copies through semi-conservative DNA replication.
New plasmids are pulled to opposing poles by the spindle fibres.
The bacterium divides in two.

27. https://youtu.be/x00otjSL6GQ

28. Prokaryotes divide by binary fission.
Life cycle of E. coli from:

29. What about conjugation?