Evolution

Alan Ward

Evolution

Formation of the EarthGeochemical dating places the Earth’s age at 4.6 billion years

The oldest rocks:

SW Greenland – Itsaq Gneiss Complex (3.86 billion years old)•Volcanic•Carbonate•Sedimentary

Western Australia – Warrawoona seriers; Towers formation; Pilbara supergroups

South Africa – Swaziland supergroup

Evolution

Hadean

ArcheanOldest rocks from Isua Supercrustal Group

Oldest fossils

Formation of the earth

Stromatolites and cyanobacterria

first eukaryotesProterozoic

Explosion of phytoplanckton

Decline in phytoplanktonCambrian explosionPlants invade the landDinosaurs

Evolution

EvolutionWays of studying the origin of life

Essential characteristics of Life

Replication

Catalysis

Boundary layer

RNA World Early cellular life Modern cellular life

proteins take over as catalysts

DNA takes over replication

Evolution

Self-replicating, catalytic RNA molecules

Ribozymes

Modern examples

Self-splicing mRNA

RNAse P

Ribosomes

50S ribosome

RNA

protein

RNA World Replication and Catalysis

Lipoprotein vesicles

The cell – a boundary layer

Schrum et al., (2010) The origins of cellular life. Cold Spring Harbour Perspect Biol . Origins of Life Sunject Collection

Energy generationEssential characteristics of Life

Proton Motive Force

or

Substrate level phosphorylation

FeS H2S + CO2 CH3SH FeS/NiS CH3SH + CO CH3COSCH3

CH3COSCH3 + Pi CH3CO-P + CH3SH

Warm little pool

RNA WorldThe ribosome is a ribozyme

DNA evolution

• replication infidelities • effects of external and internal environmental

mutagens (UV, O2, mutagens, …)• DNA rearrangements• acquisition of genetic information

Replication- Taq polymerase

Replication- Bacterial genome

Bacterial genomes are sampling rather than accumulating sequences, counterbalancing gene acquisition with gene loss

Estimated rate of acquisition by lateral gene transfer 31 kb/Myr

Point mutations introduce 22 kb of variant DNA per Myr

Total acquired DNA since divergence of E. coli and S. enterica 100 Myr ago 3Mb

DNA different by LTG between E. coli and S. enterica 803 Kb

Lateral Gene Transfer

Escherichia coli (compared to Salmonella enterica)

Lawrence JG Ochman H (1997) Amelioration of Bacterial Genomes: Rates of Change and Exchange. J Mol Evol (1997) 44:383–397

Lateral Gene Transfer

MacFadden BJ (2005) Fossil Horses— Evidence for Evolution. Science 307, 1728 – 1730