How did life arise

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Origins of Life
How did life arise? requires catalyst
s - proteins producing - metabolism prote
ins information - RNA/DNA coding -
genetics storage
E G
ATP
A B
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Many molecular building blocks can be synthesized
from a solution of simpler molecules using
electrical discharge or UV sugars CH4
NH3 CO2 H2O HCN H2CO2 amino
acids nucleotides clay polynucleotide
s
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Transition from RNA DNA high
mutation rate of RNA (modern RNA virus
mutation rate 104/nucleotide) oldest rocks
in Isua, Greenland 3.8 billion years
old ?chemical traces of life? consensus 3
3.5 billion years ago fossil cells from several
sites (Apex Chert in Western Australia 3.5
bya) early cellular life was prokaryotic,
anaerobic (CO2 atmosphere) 2 3.5 bya
stromatolites (mineralized layers of cells)
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simple inorganics replicons, catalysts
RNA DNA cellular
multicellular
chemistry, fossils
phylogeny (small subunit rRNA)
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Aminoacyl-tRNA synthetase
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Eubacteria
Mitochondria
Chloroplasts
-ATPase
Archaebacteria
Eukaryota
Eubacteria
Chloroplasts
Archaebacteria
V-ATPase
Eukaryota
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Eukaryotes 1.8 - 2.2 bya (body fossil
molecular data) organelles - mitochondria,
chloroplasts via symbiosis nucleus mitosis,
meiosis order of acquisition
uncertain association with increase in
atmospheric oxygen (2 bya) increase in
abundance of photosynthetic organisms more
efficient than prokaryotes possible advantage to
aerobic respiration (mitochondria)
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Evolution of multicellularity cell
differentiation rudimentary
development 1.5 bya (molecular clock) 1.2 bya
(fossils algae) --key innovations associated
with the development of multicellularity --cell
adhesion molecules --epithelial sheets of
cells --hierarchical gene action Ediacaran
(Australia) fossils earliest multicellular
animals 670-550 mya
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Cambrian explosion 540 mya
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What caused the Cambrian explosion?
molecular sequence data suggest that lineage
divergence occurred much earlier than the
divergence of body plans ( 1 bya)
Wray et al. 1996
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What caused the Cambrian explosion?
Ediacaran (Proterozoic) limited ecological
diversity (sessile filter feeders or water
column planktivores) Burgess Shale
(Cambrian) great increase in ecological
diversity marks the origin of hard parts
(restate question)
-- increase in atmospheric oxygen (key to
multicellularity) -- possible mass extinction of
Ediacaran fauna --gt ecological opportunity --pred
ators, especially visually hunting
predators --increase in plant (phytoplankton)
productivity leads to increased abundance and
diversity of animals (more preymore
predators) --snowball Earth pre-Cambrian had
near complete ice and glaciers