G4 Earth Evolution: Life

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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
chronology 4. 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 Com
mon ancestor to all modern life DNA based
Evidence or reasoning
DNA sequencing
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2. Establishing a list of events
Assumed steps Darwins warm
little pond Common ancestor to
all modern life DNA based
Evidence or reasoning Oparin and
Haldanes theories, 1920s 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 steps Darwins warm
little pond Common ancestor to all
modern life DNA based
Evidence or reasoning Oparin and
Haldanes theories, 1920s 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 modern organisms are
hyperthermophiles However, 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 steps Darwins warm
little pond Appearance of anaerobic heterotrophs
using surrounding molecules for growth and
reproduction Common ancestor to all
modern life DNA based
Evidence or reasoning Heterotrophs
chemically simple, but need 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 steps Darwins warm
little pond Appearance of anaerobic heterotrophs
using surrounding molecules for growth and
reproduction Transition to RNA
world Common ancestor to all modern
life DNA 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 steps Darwins 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 life DNA 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 steps Darwins 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
life DNA based
Evidence or reasoning Marg
ulis minimum cell.
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2. Establishing a list of events
Assumed steps Darwins 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 life DNA based
Evidence or reasoning Ne
cessary for sustainability. Most primitive life
does it.
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2. Establishing a list of events
Assumed steps Darwins 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 life DNA 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 steps Darwins 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 life DNA based
Evidence or reasoning During and
after meteorite bombardment. Murchison Meteorite
- 4.6 Ga After 3.8 Ga . .. . Carb
on 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 life and metazoans 1.
Prokaryotes and eukaryotes 2. Evolution of
eukaryotes 3. Eukaryote radiations 4. 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 radiations
Biologically probably split off at 3.5
Ba Palaeontologically oldest ?2.1 Ba from
Michigan BIF large cells common since 2
Ba Acritarchs 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