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 Slide 2 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
Slide 3 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? Slide 4 2.
Establishing a list of events Assumed steps Common ancestor to all
modern life DNA based Evidence or reasoning DNA sequencing Slide 5
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 CH
4, NH 3, H 2 and H 2 O 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. Slide 6 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 CH 4, NH 3, H 2 and H 2 O 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. Slide 7 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. Slide 8 2. Establishing a
list of events Slide 9 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. Slide 10 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 Slide 11 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 Margulis minimum cell. Slide 12 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 Necessary for sustainability. Most primitive life does
it. Slide 13 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. Slide 14 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 . .. .
Carbon isotopes go light very early - around 3.8 Ba. Stromatolites.
(Oldest fossils disputed, oldest definite fossils 2.5 Ba from
Transvaal Supergroup) Slide 15 3. Establishing a possible
chronology Slide 16 4. Archaean life Slide 17 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 Slide 18 1. Prokaryotes
and eukaryotes Slide 19 2. Evolution of eukaryotes Slide 20 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 Slide 21 4.
Origin of metazoans Slide 22 Slide 23 5. The PreCambrian-Cambrian
boundary Slide 24
