History of Life on Earth

1. History of Life on Earth Chapter 25

2. Overview • First Cells • Major Life events • Fossil Record • Geologic Time scale • Mass extinctions • Continental Drift

3. What was Early Earth like?

4. What do we really know about the first living organism??

5. Can we take Darwin’s theory all the way back to the Origin of Life?

6. What were the major milestones in the Evolution of Life?

7. How long ago was that ?

8. Getting used to the geologic time scale… • We use • Millions of years (MYA) and • Billions (BYA) of years ago. • One Million Years: If we give 10,000 years for all of recorded human history • One million years equals 100 times all human history. • Enough time for 30,000 generations

9. Evolutionary Clock • Eras not to scale • “Our” world, with plants and animals on land is not very old • Protists and Bacteria / Archae have been around longer and are more diverse.

10. Fig 25-UN11 Ceno- zoic Meso- zoic Paleozoic Origin of solar system and Earth 4 1 Proterozoic Archaean years ago Billions of 2 3

11. Geologic Time Scale Table 25.1 Know : • Eons • Phanerozoic • Proterozoic • Archaean • 4 eras • Their dates • Major Animal and Plant groups • “Precambrian” Era • Periods: • Permian • Cretaceous (K) • Tertiary (T)

12. The three Eras andthe new groups that begin to dominate on land • Cenozoic – 65.5 MYA • Mammals, birds flowering plants • Mesozoic – 251 MYA • Reptiles, conifers • Paleozoic – 542 MYA • Amphibians, insects, moss, ferns • Precambrian (2 eons) – 4.6 BYA • Origin of animal phyla • Protists, bacteria

13. The three Eons andthe new groups that begin to dominate on land Eons: • Phanerozoic – Present to 542 MYA “Precambrian”: • Proterozoic - 542- 2,500 MYA • Origins of Eukaryotes • Archaean – 2,500- 4,500 MYA • bacteria, and oxygen atmosphere

14. Four Eras • Eras do not have same amount of time • Pace of evolution quickens with each major branch or era . • Recent organisms generally are more complex – older ones simpler. • Why ?

15. Key Events in the History of Life on Earth • 4.6 BYA Formation of Earth • Origins of Biomolecules • Formation of Polymers • Origin of Protobionts; Self replicating RNA-DNA; Metabolism; Evolution • 3.5 BYA Formation of first cell – prokaryotes

16. Key Events in the History of Life on Earth • 2.7 BYA Origin of Oxygen generating photosynthesis • 1.5 BYA Origin of Eukaryote cells • 1.2 BYA – 565 MYA Multicellularity • 535 MYA Cambrian Explosion • 500 MYA Colonization of land

17. Fig 25-UN8 1.2 bya: First multicellular eukaryotes 535–525 mya: Cambrian explosion (great increase in diversity of animal forms) 500 mya: Colonization of land by fungi, plants and animals 2.1 bya: First eukaryotes (single-celled) 3.5 billion years ago (bya): First prokaryotes (single-celled) 500 1,000 1,500 4,000 3,000 3,500 2,500 2,000 Present Millions of years ago (mya)

18. Fig. 25-4 Rhomaleosaurus victor, a plesiosaur Present Dimetrodon 100 million years ago Casts of ammonites 175 200 270 300 Hallucigenia 4.5 cm 375 Coccosteus cuspidatus 400 1 cm Dickinsonia costata 500 525 2.5 cm 565 Stromatolites Tappania, a unicellular eukaryote 600 3,500 1,500 Fossilized stromatolite

19. Fig. 25-10 500 Sponges Cnidarians Molluscs Annelids Chordates Arthropods Brachiopods Echinoderms Early Paleozoic era (Cambrian period) Millions of years ago 542 Late Proterozoic eon

20. How did Life come into being ?

21. Spontaneous generation ? • Life from non-living matter. • Mice from wet hay makes mice • Refute for animals, and plants in 1600’s. • Still thought to be the case for microbes, until Pasteur.

22. Louis Pasteur(1822-1895) • Disproved spontaneous generation • Showed that biogenesis alone accounted for new cells • Invented Pasteurization

24. Biogenesis • Life (whole organisms) comes from reproduction of other preexisting life. • Later, the cell theory will be similar • all cells come from preexisting cells.

25. What about the first Cell? • Scientists think, first cell-like structures came from non living matter. • What would be needed to make a cell from scratch ?

26. Origin of life - • Need to have biomolecules: • Complex Carbohydrates • Proteins • Lipids • Nucleic acids • To make membranes,enzymes, DNA and all the other cellular components.

27. Where did biomolecules come from? • Today only living organisms make biomolecules

28. “Arm Chair” science • Still mostly untested hypotheses, and conjecture. • Trying to test hypotheses by making artificial cells in labs.

29. Conditions on Earth 4 BYAOparin – Haldane 1920’s chemists • No free Oxygen – No Ozone layer • More uv radiation • Reducing (electron rich) atmosphere • More lightning • Meteorite bombardment • More volcanic activity • H20, Methane (CH4), Ammonia (NH3)

30. Energy rich early earth

31. Urey & Miller - 1953 • Used Oparin / Haldane ideas of earth earth conditions • Made an apparatus to mimic early earth conditions • Let run and tested fluid for compounds • Found simple sugars, amino acids, and other organic compounds.

32. Stanley Miller

34. Significance: Abiotic synthesis of macromolecules

36. Ribozymes • RNA self replication before enzymes? • RNA before DNA

37. Hypothetical Protobionts

38. Not “facts” but working hypotheses • Lab experiments can only show what could have happened • Other thoughts: • Deep sea vents – constant environment, chemical energy • Panspermia or microbes from meteorites • Most like our understanding will change greatly in future.

39. Universal Common Ancestor • Hypothetical • Would be cell from which all modern life has descended • Have things that ALL living organisms share: • Phospholipid bilayer cell membrane • Use DNA/ RNA for genes, and make proteins from the genetic code • Glycolysis, ATP in their metabolism

40. Fossil Record • Fossil any preserved remnant or impression of an organism that lived in the past • Most form in sedimentary rock, from organisms buried in deposits of sand and silt. Compressed by other layers. • Also includes impressions in mud • Most organic matter replaced with minerals by Petrification • Some fossils may retain organic matter • Encased in ice, amber, peat, or dehydrated • Pollen

41. Fossil Formation –

43. Radiometric “absolute” dating

44. Dating Fossils • “Absolute” Radiometric dating: decay and half-life of natural isotopes. • Index dating – comparing index fossils in strata Brachiopod index fossils

46. Many changes in geologic history due to Plate tectonics

47. Crust 35 km (21 mi.) avg., 1,200˚C 100 km (60 mi.) 200 km (120 mi.) Low-velocity zone Crust Mantle Lithosphere Solid 10 to 65km Asthenosphere (depth unknown) 2,900km (1,800 mi.) 3,700˚C 100 km Outer core (liquid) 200 km Core 5,200 km (3,100 mi.), 4,300˚C Inner core (solid) Layers of the Earth

48. Plate tectonics • The study of the movement of earth structures in the crust. • Internal forces from the core create heat that keeps asthenosphere molten. • Convection cells • Mantle Plumes

49. Convection Cell in Mantle

50. Earth’s Layers - Crust • Oceanic Crust • only 3 miles thick • Continental Crust • up to 12-40 miles thick • Oceans change shape much more than continents. • These land movements we call Plate Tectonics, and cause earthquakes.