Chapter 26 ~ Early Earth and The Origin of Life

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- LazzaroSpallanzani(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 didnot 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 750 - 570

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