1. Unit 1 - The Origins of Life
Louis Pasteur
December 27, 1822 –
September 28, 1895

2. Pasteur’s swan neck flask

3. Pasteur’s sour wine

4. Radiometric dating of rocks (amîtsoq gneisses) from
The Earth Is Old!
Radiometric dating of rocks (amîtsoq gneisses) from
Western Greenland
Similar results from Australia, Wisconsin, Africa and Russia

5. Cyanobacterial microfossils

6. Extant stromatolites

7. Fossilized stromatolites

9. -Woese, Micro. Rev., 1987
The dilemma faced by microbiologist is that many bacteria look the same. It’s fairly to distinguish between the various plants and animals in a setting like this. But the two microbial species in these electron micrographs are all but indistinguishable.
In 1977 a fella by the name of Carl Woese at the Univerity of Illinois changed all that. By comparing the DNA of many different organisms he convincingly showed the biological world, rather than 5 kingdoms, was more appropriately divided into three domains of living things: the Bacteria, the Archaea and the Eukarya. (You are here - point to humans).
This is a phylogenetic tree. A tree of the similarity between the DNA of one organism and another. The shorter the distance between two organisms the more similar the DNA and by implication the more closely related they are.
Based on Dna evidence these two organisms are vastly different. More divergentt than plants are from animals.
One thing that you will note is that this tree does away with the hierarchy of the 5-kingdom scheme. The tip of each of these branches represents a living organism but it does not imply that one organism is more advanced than another - only genetically different. We’ll come back to this point in a couple of minutes.

10. Prokaryotes
Eukaryotes

12. Archaea Chlamydia Low G+C gram positive Actinobacteria Cytophagales
Planctomycetes
Chlamydia
Verrucomicrobia
OP3
Acidobacterium
Termite group I
Nitrospira
Synergistes
OP10
OS-K
Flexistipes
Low G+C gram positive
OP8
WS1
Cyanobacteria
Actinobacteria
Green non-sulfur
Fibrobacter
OP5
Marine group A
OP9
Green sulfur
Dictyoglomus
Cytophagales
Coprothermobacter
Thermus/Deinococcus
Thermotogales
Thermodesulfobacterium
Spirochetes
TM6
Aquificales
W88
TM7
0.10
Fusobacteria
Proteobacteria
OP11
Archaea
J. Bacteriol. 1998; 180: