Geology 1: Palaeontology

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Geology 1 Palaeontology Lecture 1 Origin of
life
1. How to study origins 2. What is
life? Categories of living organisms What life
requires and produces 3. The evidence for
origins 4. A narrative of early evolution 5.
Evolution of more complicated life forms
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1. How to study the origin of life
Interaction with atmosphere
Grades of organisation - simplest modern life
What life needs
Fossils
likely narrative likely chronology
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2.1 What is life ?
Living systems can - 1. Fight entropy - be
complex and highly organised 2. Be
homeostatic - survive over a period of time 3.
Take energy from the environment 4.
Respond to external stimuli 5. Reproduce -
transmit information between generations -
evolve and adapt.
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2.2 Types of life
1. Multicelled animals (metazoans)
2. Multicelled plants
4. Prokaryotes
3. Eukaryotes
5. A hypothetical minimum cell
6. Replicating molecules
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2.3 What life needs
Carbon Liquid water Energy Phosphorus
2.4 What life produces
CO2 O2 12C enrichment in rocks Body fossils
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3.1 Evidence for origins - geology
A. After 4.55 Ba B. After 4 Ba C.
Before oldest fossils at 3.5 Ba D. ?Before
oldest sediments at 3.8 Ba
Earth forms
Meteorites subside
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3.2 Evidence from fossils
Oldest fossils 3.5 Ba (for last decade) 1.
Onverwacht Group (Swaziland Supergroup), South
Africa 2. Warrawoona Group (Pilbara Supergroup),
Western Australia
Cell chain Stromatolites
Both Prokaryotes
Nb Biological evidence suggests split between
prokaryotes and eukaryotes at about 3.8 Ba
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3.3 Evidence from the atmosphere
A. Evidence for O2 Banded iron formations
3.5-1.8 By Pyrite conglomerates 2.8 - 2.0
By B. For photosynthesis Isotopically light
carbon (more carbon-12 than would be expected
in abiotic situation) Isua rocks slightly
light (3.8 Ba) All carbonates lt 3.5 Ba very light
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4. Narrative of origin and evolution of life
Ba 4.55 Earth forms 4.00 Meteorites
subside molecules replicate minimum cell
appears photosynthetic prokaryotes 3.8 Oldest
sediments limited diversification 3.5 Oldest
fossils prokaryotes dominate eukaryotes
rare 2.1 Oldest large cell - subject of next
lecture