G4 Earth Evolution: Life Lecture 1: Origin of life and complex life. Myth marketing and hype.
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Transcript of G4 Earth Evolution: Life Lecture 1: Origin of life and complex life. Myth marketing and hype.
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G4 Earth Evolution: Life
Lecture 1: Origin of life and complex life. Myth marketing and hype.
Lecture 2: Proterozoic life and metazoans
Lecture 3: The Phanerozoic record and exceptional preservation
Lecture 4: Effects of life on Earth and non-Uniformitarianism
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Lecture 1: Origin of life and complex life. Myth marketing and hype.
1. What can be known about the evolution of life?2. Establishing a list of events
3. Establishing a possible chronology4. Archaean life
5. Evolution of complexity
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1. What can be known about the evolution of life?
Lazcano, 2001‘Of necessity, work on the origin of life should be regarded
as enquiring and explanatory rather than definitive and conclusive….the issue should be addressed conjecturally in an attempt to construct a coherent historical narrative.’
Hence influenced by scientific and cultural fashions, for example,the possibility of life originating on Mars
early heterotrophy in a ‘Dog-eat-Dog’ social climate.
Is a scientist allowed to not know something?
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2. Establishing a list of events
Assumed steps
Common ancestor to all modern lifeDNA based
Evidence or reasoning
DNA sequencing
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Common ancestor to all modern lifeDNA based
Evidence or reasoningOparin and Haldane’s theories, 1920’s
Miller experiments (eg 1993) - electrical discharges for 1 week over a mixture of CH4, NH3, H2 and H2O produced organic molecules including amino acids and urea.
Importance of HCN - polymers denature to produce amino acids, purines, and adenine.
Evidence from the Murchison Meteorite - 4.6 Ga,includes array of protein and non-protein amino acids, purines, pyramidines, hydrocarbons and evidence of liquid water.
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Common ancestor to all modern lifeDNA based
Evidence or reasoningOparin and Haldane’s theories, 1920’s
Miller experiments (eg 1993) - electrical discharges for 1 week over a mixture of CH4, NH3, H2 and H2O produced organic molecules including amino acids and urea.
Importance of HCN - polymers denature to produce amino acids, purines, and adenine.
Evidence from the Murchison Meteorite - 4.6 Ga,includes array of protein and non-protein amino acids, purines, pyramidines, hydrocarbons and evidence of liquid water.
Most primitive modernorganisms are hyperthermophilesHowever, rapid decay of most organic molecules at high temperatures makes this unlikely for the pond.
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Common ancestor to all modern lifeDNA based
Evidence or reasoning
Heterotrophs chemically simple, butneed a convincing method of carrying information through time.
RNA? But ribose and phosphate esters chemically unlikely in chemical soup.
Maybe modified nucleic acid sugar-phosphate backbones , maybe another self-replicating molecule, maybe something like prions.
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2. Establishing a list of events
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Common ancestor to all modern lifeDNA based
Evidence or reasoning
RNA is catalytic and encoding. Used in primitive reproduction today.
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Darwinian evolution towards dominance of DNA
Common ancestor to all modern lifeDNA based
Evidence or reasoning
This is what we see today. Better fidelity of information carriage
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Darwinian evolution towards dominance of DNA
Evolution of primitive cells
Common ancestor to all modern lifeDNA based
Evidence or reasoning
Margulis minimum cell.
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Darwinian evolution towards dominance of DNA
Evolution of primitive cells
Evolution of autotrophy
Common ancestor to all modern lifeDNA based
Evidence or reasoning
Necessary for sustainability. Most primitive life does it.
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2. Establishing a list of events
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Darwinian evolution towards dominance of DNA
Evolution of primitive cells
Evolution of autotrophy
Common ancestor to all modern lifeDNA based
Evidence or reasoning
All molecular trees show a single, common root to the tree of life.
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3. Establishing a possible chronology
Assumed stepsDarwin’s warm little pond
Appearance of anaerobic heterotrophs using surrounding molecules for growth and reproduction
Transition to RNA world
Darwinian evolution towards dominance of DNA
Evolution of primitive cells
Evolution of autotrophy
Common ancestor to all modern lifeDNA based
Evidence or reasoningDuring and after meteorite bombardment. Murchison Meteorite - 4.6 GaAfter 3.8 Ga
……….
………..
……….
Carbon isotopes go light very early - around 3.8 Ba. Stromatolites.(Oldest fossils disputed, oldest definite fossils 2.5 Ba from Transvaal Supergroup)
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3. Establishing a possible chronology
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4. Archaean life
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Lecture 2: Proterozoic lifeand metazoans
1. Prokaryotes and eukaryotes2. Evolution of eukaryotes
3. Eukaryote radiations4. Evolution of metazoans
5. PreCambrian-Cambrian boundary
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1. Prokaryotes and eukaryotes
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2. Evolution of eukaryotes
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3. Eukaryotic radiationsBiologically: probably split off at 3.5 BaPalaeontologically: oldest ?2.1 Ba from Michigan BIF
large cells common since 2 BaAcritarchs: unequivocal eukaryotes, probably dinoflagellate cysts
from 1.7 Ba common from 1 Ba
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4. Origin of metazoans
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4. Origin of metazoans
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5. The PreCambrian-Cambrian boundary
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5. The PreCambrian-Cambrian boundary