1. Chapter 26 ~ Early Earth and The Origin of Life

2. Early history of life Solar system~ 12 billion years ago (bya)
Earth~ 4.5 bya
Life~ 3.5 to 4.0 bya
Prokaryotes~ 3.5 to 2.0 bya stromatolites
Oxygen accumulation~ 2.7 bya photosynthetic cyanobacteria
Eukaryotic life~ 2.1 bya
Muticelluar eukaryotes~ 1.2 bya
Animal diversity~ 543 mya
Land colonization~ 500 mya

3. Stromatolites

4. Little bit of history: Antoni van Leeuwenhoek- animalcules (1675)
Spontaneous generation- John Needham (1750)
Biogenesis- Lazzaro Spallanzani(1767), Rudolf Virchow(1858) and Luis Pasteur (1861)

5. The Origin of Life Spontaneous generation vs. biogenesis
Needham vs. Pasteur

6. The Origin of Life The 4-stage Origin of life Hypothesis:
1- Abiotic synthesis of organic monomers
2- Monomers into Polymers
3- Molecule packaging (“protobionts”)
4- Origin of Self-replicating molecules

7. Organic monomers/polymer synthesis
Oparin (Rus.)/Haldane (G.B.): 1920
Hypothesis: primitive earth atmosphere allowed inorganic precursors to synthesize organic compounds (abiotic process)
reducing atmosphere from volcanic vapors with lightning & UV radiation enhances complex molecule formation (no O2)
Oceans were a solution of organic molecules or “primitive soup” from which life arose

8. Organic monomers/polymer synthesis
Miller/Urey experiment(1953):
Tested Oparin and Haldane’s hypothesis
Hydrogen (H2), methane (CH4), ammonia(NH3), represented early atmosphere
Water represented early seas
Electrodes simulated lightning
Condenser cooled gases to simulate rain

10. Millers results:
periodically collection and analyzing samples: the following was found-
Oily hydrocarbons
Variety of amino acids
Nitrogen bases
ATP

11. Organic monomers/polymer synthesis
Other scientist discovered abiotic polypeptides or proteinoids
Formed from dripping organic monomers on hot sand, clay or rock.

12. Organic monomers/polymer synthesis
(More abiotic synthesis of organic compounds)
Coacervates = tiny, spherical droplets of organic molecules (proteins, carbs, lipids) formed via hydrophobic forces
Proposed by Oparin in his version of the biogenesis theory

13. coacervates

14. Today: -Miller and Urey = debate
- many scientist believe that atmosphere did not play a significant role in the abiotic formation of organic compounds
Submerged volcanoes and hot deep sea vents probably provided early resources
Exampe: Inorganic sources of sulfur and iron could have been used to produce energy(ATP)

15. Other sources for organic compounds:
Nitrogen bases such as Adenine have been formed from cyanide reactions in the clouds of dust between stars
Meteorites carry the organic materials to earth

16. Abiotic genetic replication
What was the first genetic material?
DNA or RNA?
Scientists are making a case for RNA

17. Evidence for RNA as first genetic material:
1. Ribozymes:
RNA catalysts
Can make complementary copies of short pieces of RNA
Self splicing
Can excise pieces of different molecules
autocatalytic

18. Evidence for RNA as first genetic material:
2. Laboratory observations of natural selection:
RNA can conform to many different shapes
Can interact with surrounding molecules
Certain base sequences could be more stable and replicate faster

19. Abiotic genetic replication

21. Evidence for RNA as first genetic material:
3. RNA molecules have the capacity to store information
RNA molecules replicate information
Can assist in the formation of peptides (modern function of RNA in ribosomes)
RNA could have acted as a template for DNA nucleotides to assemble
All of this MAY have taken place in protobionts

22. Evidence of Biological Evolution:
1. Geographical
2. Geological
3. Physical
4. Chemical
5. Mathematical Applications
6. Molecular
7. Morphological
8. Genetic

23. How is early life on Earth chronicled?
Radiometric dating:
Carbon-14 (good for 50,000 years)
Potassium-40
Magnetic dating: alignment of iron particles frozen in ancient rock with the earth’s magnetic field
Magnetic reversals
Thermoluminescence: heating electrons, measuring and analyzing the light emitted.

24. Morphological Evidence:
Morphological homologies:
Embryology
Vestigial structures

25. Biochemical and genetic evidence:
mtDNA:
Y-chromosome
DNA sequencing

26. Mathematical Models: Graphical analysis of allele frequencies
BLAST
Phylogenic trees
Sequencing data

27. Geological Record: 1. Archeaen Eon 2. Proterozoic Eon
3. Phanerozic Eon

28. Evidence of evolution within changing environments:
Speciation and Extinction
Five major mass extinctions
Human impact

29. Mass Extinctions:
Two Mass Extinctions have received the most attention:
Permian
Cretaceous

30. Permian Mass Extinction:
Permian period- defines the boundary between the Mesozoic and Paleozoic eras.
251 million years ago
96% of aquatic life went extinct (and some terrestrial life)
Occurred in less than 5 million years
Volcanic eruptions in Siberia

31. Cretaceous Mass Extinction:
Cretaceous period marks the boundary between Mesozoic and Cenozoic eras.
65 million years ago
Killed more than half of the aquatic life
Exterminated many families of terrestrial plants and animals
Most if not all Dinosaurs

32. Cretaceous continued:
Large comet(10km)collided with the Earth:
Evidence:
Crater at the Yucatan Penninsula (chicxulub crater- 180 km in diameter)
Thin layer of clay enriched Iridium that separates the Mesozoic from the Cenozoic eras
Caused a spike in volcanic activity

33. Prokaryotic Exploitation:
Stromatolites
Oldest known fossils- 3.5 billion years
Layers of bacteria and sediment
Autotrophs and Heterotrophs:
Evolved from protobionts
Only life forms on earth for 1.5 billion years
Nonoxygenic photosynthesis- chemisomotic synthesis of ATP.

34. Photosynthesis and Oxygen Revolution:
Enter cyanobacteria
Saturated oceans with oxygen
Formation of oxides (FeO)
Accumulates as sediments
Compressed into rock
Oxygen gas bubbles out of oceans into atmosphere
Atmosphere goes from reducing to oxidizing.

35. Genesis of Eukaryotes:
Oldest Eukaryotic Fossils: 2.1 billion years ago??
Endosymbiosis- hypothesis that explains how large complex eukaryotes evolved from smaller prokaryotic cells.
Undigested prey
Parasites
Eventually became mutually benefitial

36. What came first?
Mitochondria or the Chloroplast??

37. Genetic Chimeras:
Composed of different populations of genetically different cells.
Mitochondria, chloroplasts and nuclear genomes come from different forms of bacteria.

38. Genetic Annealing:
Gene transfer between many different bacterial lineages
Eukaryotic cells may be a product of this process.

39. Multicellularity:
Oldest multicellular organisms = 1.5 – 1.2 billion years ago.
Limited to size because of ice age
Between

40. The Colonial Connection:
Multicellular organisms lived in colonies.
Autonomous
Self replicating
differentiating

41. The Cambrian Explosion:
First 20 million years of the Cambrian period most of the major phyla of animals suddenly appear
About 1 billion to 700 million years ago
Animals with exoskeletons and hard shells

42. Colonization of land: 500 million years ago Macroscopic life:
Plants
Fungi
Animals
What are some major problems that terrestrial organisms had to over come?

43. Continental Drift: Pangea Spatial distribution of life
Reshapes biological diversity
Mesozoic- continents start to drift
Created separate zones of evolution with different lineages of plants and animals

44. Taxonomy: Linnaeus: First classification system
Divided all forms of life into two categories
Plants and Animals

45. Robert H. Whittaker: Cornell University
Created five kingdom system of classification
Monera (bacteria- prokaryotic cells)
Protista- single celled eukaryotes
Fungi – multicellular eukaryotes
Plants- multicellular eukaryotes
Animals- multicellular eukaryotes

46. Three Domain System:
Three Super Kingdoms:
Bacteria
Archaea
Eukarya

47. Universal Ancestor: Four Characteristics:
The cell was surrounded by a lipid cellular membrane
Genetic code based on DNA
The genetic code was expressed with single stranded RNA intermediates
The cell multiplied and duplicated all of its contents, followed by cell division

48. The Major Lineages of Life