Download I. Earth History

Origin of Life Hypotheses
4.5 bya: Earth Forms
I. Earth History
I. Earth History
- Earliest Atmosphere - probably of volcanic origin
Gases produced were probably
similar to those created by
modern volcanoes (H2O, CO2,
SO2, CO, S2, Cl2, N2, H2) and
NH3 and CH4
4.0 bya: Oldest Rocks
4.5 bya: Earth Forms
I. Earth History
4.0 bya: Oldest Rocks
3.5 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
4.0 bya: Oldest Rocks
3.5 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
Stromatolites - communities of layered 'bacteria'
2.3-2.0 bya: Oxygen in
Atmosphere
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
0.9 bya: first animals
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
0.5 bya: Cambrian
0.9 bya: first animals
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.9 bya: first animals
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
0.9 bya: first animals
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
0.9 bya: first animals
1.8 bya: first eukaryote
2.3-2.0 bya: Oxygen
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
4.5 bya: Earth Forms
I. Earth History
4.5 million to present
(1/1000th of earth
history)
II. Origin of Life Hypotheses
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
Aleksandr Oparin
(1894-1980)
J.B.S. Haldane
(1892-1964)
II. Origin of Life Hypotheses
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
all biologically important
monomers have been
produced by these
experiments, even while
changing gas composition
and energy sources
II. Origin of Life Hypotheses
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox - 1970 - polymerized protein microspheres
II. Origin of Life Hypotheses
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox - 1970 - polymerized protein microspheres
- Cairns-Smith (1960-70) - clays as templates for non-random
polymerization
- 1969 - Murcheson meteorite - amino acids present; some not found on
Earth. To date, 74 meteoric AA's.
- 2004 - Szostak - clays could catalyze
formation of RNA's
III. Acquiring the Characteristics of Life
A. Three Primary Attributes:
- Barrier (phospholipid membrane)
- Metabolism (reaction pathways)
- Genetic System
III. Acquiring the Characteristics of Life
B. Barrier (phospholipid membrane)
- form spontaneously in aqueous solutions
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- problem:
how can pathways with useless intermediates evolve?
These represent 'maladaptive valleys', don't they?
A
B
C
D
How do you get from A to E, if B, C, and D are non-functional?
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
A
B
C
D
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env.
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env.
As protocells gobble it up, the concentration drops.
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
D
Anything that can absorb something else (D) and MAKE E is
at a selective advantage...
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
D
Anything that can absorb something else (D) and MAKE E is
at a selective advantage...
but over time, D may drop in concentration...
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
C
D
So, anything that can absorb C and then make D and E will
be selected for...
E
III. Acquiring the Characteristics of Life
C. Metabolic Pathways
- Solution - reverse evolution
A
B
C
D
and so on until a complete pathway
evolves.
E