1. Origin of Life Hypotheses

2. Origin of Life Hypotheses
Evolutionary Theory

3. A. The Early Earth and Earth History
4.5 bya: Earth Forms
Graviational sorting of materials…heavy to the core, gases released under pressure…

4. The Early Earth and Earth History
- Earliest Atmosphere - probably of volcanic origin
Gases produced were probably similar to those released by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 and CH4

5. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks

6. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
Stromatolites - communities of layered 'bacteria'

7. A. The Early Earth and Earth History
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils
Putative microfossil bacteria from Australia that date to 3.4 by

8. - the first cells were probably heterotrophs that simply absorbed nutrients and ATP from the environment.
- as these substances became rare, there was strong selection for cells that could manufacture their own energy storage molecules.
- the most primitive cells are methanogens (Archaea), but these are NOT the oldest fossils.

9. - the second type of cells were probably like green-sulphur bacteria, which used H2S as an electron donor, in the presence of sunlight, to photosynthesize.

10. IV. Early Life
- about 3.2 bya, “banded iron” formations occur… these are formed by the oxidation of dissolved iron and Sulphur … removal of electrons by primitive ‘non-oxygenic’ photosynthesis, resulting in rusty precipitates of iron .

11. A. The Early Earth and Earth History
“Red Beds”
bya: Oxygen in Atmosphere
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

12. - the evolution of oxygenic photosynthesis was MAJOR
- the evolution of oxygenic photosynthesis was MAJOR. It allowed life to exploit more habitats, and it produced a powerful oxidating agent!

13. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

15. Eukaryote Characteristics
- membrane bound nucleus
- organelles
- sexual reproduction

16. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

17. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

18. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

19. A. The Early Earth and Earth History
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

20. A. The Early Earth and Earth History
4.5 million to present
(1/1000th of earth history)
bya: Oxygen
1.8 bya: first eukaryote
0.9 bya: first animals
0.5 bya: Cambrian
0.24 bya:Mesozoic
0.065 bya:Cenozoic
4.5 bya: Earth Forms
4.0 bya: Oldest Rocks
3.4 bya: Oldest Fossils

21. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
Aleksandr Oparin
( )
J.B.S. Haldane
( )

22. B. The Formation of Biologically Important Molecules
- 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

23. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox polymerized protein microspheres

24. B. The Formation of Biologically Important Molecules
- Oparin-Haldane Hypothesis (1924):
- in a reducing atmosphere, biomonomers would form spontaneously
- Miller-Urey (1953)
- Sydney Fox polymerized protein microspheres
- Cairns-Smith ( ) - clays as templates for non-random polymerization
Murcheson meteorite - amino acids present; some not found on Earth. To date, 74 meteoric AA's.
Szostak - clays could catalyze
formation of RNA's

25. C. Acquiring the Characteristics of Life
Three Primary Attributes:
- Barrier (phospholipid membrane)
- Metabolism (reaction pathways)
- Genetic System

26. C. Acquiring the Characteristics of Life
1. Evolution of a Membrane
- form spontaneously in aqueous solutions

27. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- problem:
how can pathways with useless intermediates evolve? These represent 'maladaptive valleys', don't they? A B C D E
How do you get from A to E, if B, C, and D are non-functional?

28. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution A B C D E

29. E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env. E

30. E C. Acquiring the Characteristics of Life Evolution of a Membrane
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

31. D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
Anything that can absorb something else (D) and MAKE E is at a selective advantage... D E

32. D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
Anything that can absorb something else (D) and MAKE E is at a selective advantage...
but over time, D may drop in concentration... D E

33. C D E C. Acquiring the Characteristics of Life Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution
So, anything that can absorb C and then make D and E will be selected for... C D E

34. A B C D E C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
- Solution - reverse evolution A B C D E
and so on until a complete pathway evolves.

35. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
DNA
RNA (m, r, t)
protein

36. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
DNA
DNA stores info, but proteins are the metabolic catalysts...
RNA (m, r, t)
protein

37. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
- Ribozymes
info storage AND
cataylic ability

38. C. Acquiring the Characteristics of Life
Evolution of a Membrane
Metabolic Pathways
Evolution of a Genetic System
- conundrum... which came first, DNA or the proteins they encode?
- Ribozymes
- Self replicating molecules
- three stage hypothesis

39. Stage 1: Self-replicating RNA evolves

40. (REPLICATION ENZYMES)
Stage 1: Self-replicating RNA evolves
RNA
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 2: RNA molecules interact to produce proteins... if these proteins assist replication (enzymes), then THIS RNA will have a selective (replication/reproductive) advantage... chemical selection.

41. (REPLICATION ENZYMES)
DNA
Reverse transcriptases
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

42. Can this happen? Are their organisms that read RNA and make DNA?

43. Can this happen? Are their organisms that read RNA and make DNA?
yes - retroviruses....

45. (REPLICATION ENZYMES)
DNA
m- , r- , and t- RNA
Already have enzymes that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

46. (REPLICATION ENZYMES)
DNA
m- , r- , and t- RNA
Already have enzymes that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA; existing replication enzymes replicate the DNA and transcribe RNA.

47. (REPLICATION ENZYMES)
This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation).
DNA
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA...

48. (REPLICATION ENZYMES)
This is adaptive because the two-step process is more productive, and DNA is more stable (less prone to mutation).
DNA
And that's the system we have today....
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of replicating the RNA...

49. D. Summary:
STEPS REQUIRED FOR THE SPONTANEOUS, NATURAL FORMATION OF LIFE, and the evidence to date:
1. Spontaneous synthesis of biomolecules - strong evidence; Miller-Urey experiments.
2. Polymerization of monomers into polymers (proteins, RNA, sugars, fats, etc.) - strong evidence;  Fox and Cairns-Smith experiments.
3. Formation of membranes - strong evidence; behavior of phospholipids in solution.
4. Evolution of metabolic systems - reasonable hypotheses, and genetic similarity in genes involved in particular pathways (suggesting gene duplication and subsequent evolution of new genes and elaboration of existing pathways)
5. Evolution of a genetic system - a reasonable hypothesis and significant corroborating evidence that it could happen. But no experimental evidence of the process evolving through all three steps.
6. How did these three elements (membrane, metabolism, genetic system come together?) a few untested hypotheses.

50. IV. Early Life
Woese - r-RNA analyses reveal a deep divide within the bacteria

51. IV. Early Life

52. IV. Early Life

53. IV. Early Life
Curiously, the very root of life may be invisible to genetic analysis. Bacteria transfer genes by division (to 'offspring'), but they also transfer genes "laterally" to other living bacteria. This makes reconstructing bacterial phylogenies difficult.

54. IV. Early Life
So, reconstructing the patterns of relatedness among these ancient life forms is difficult.
Different genes give different patterns of relatedness among domains

55. IV. Early Life
C. Domains - "Ring of Life" hypothesis (2004)