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Chapter 15: Tracing Evolutionary History

Chapter 15: Tracing Evolutionary History. NEW AIM: How has life evolved over the past 3.5 billion years?. - the major changes in the history of life on Earth. Macroevolution. - Evolution on the grand scale, above the level of a single species. - development of new species, extinction, etc….

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Chapter 15: Tracing Evolutionary History

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  1. Chapter 15: Tracing Evolutionary History NEW AIM: How has life evolved over the past 3.5 billion years? - the major changes in the history of life on Earth Macroevolution - Evolution on the grand scale, above the level of a single species - development of new species, extinction, etc… - origin of evolutionary novelties (feathers) How do scientists trace (follow) macroevolution? - fossil record

  2. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale - built using evidence from the sequence of fossils in rock – shows macroevolution Time Eras Periods Epochs

  3. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale How do scientists decide when one era/period ends and a new one begins? Mass Extinctions and Emergence of very different species

  4. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale Cambrian Explosion 540 MY ago — rapid appearance of most major groups of complex animals

  5. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale Mass Extinctions 251 MY ago — Earth's largest extinction (the P/Tr or Permian-Triassic extinction event) - killed 96% of all marine species and an estimated 70% of land species (including plants, insects, and vertebrate animals). Created the opportunity for dinosaurs to become the dominant land vertebrates…the Great Dying

  6. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale Mass Extinctions 65 MY ago — (the K/T or Cretaceous –Tertiary extinction event) - about 50% of all species became extinct. Ended reign of dinosaurs and opened the way for mammals to become the dominant land vertebrates.

  7. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale Mass Extinctions 65 MY ago — (the K/T or Cretaceous –Tertiary extinction event) - about 50% of all species became extinct. Ended reign of dinosaurs and opened the way for mammals to become the dominant land vertebrates.

  8. Chapter 15: Tracing Evolutionary History AIM: How has life evolved over the past 3.5 billion years? Geological Time Scale Mass Extinctions The Holocene Extinction — possibly one of the fastest ever: humanity's destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years.

  9. Chapter 15: Tracing Evolutionary History NEW AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) * There is a somewhat fixed ratio of 14C to 12C in the atmosphere * All living organisms should have the same ratio of 14C to 12C in our bodies (we eat carbon from the atmosphere) * So we know the 14C to 12C ratio in living organisms

  10. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) What happens to 14C over time?

  11. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) What happens to 14C over time? * 14C is always decaying to 14N

  12. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) Assumptions: * Ratio of 14C: 12C in a living organism is that same as the atmosphere * 14C is always decaying to 14N So what happens when an organism dies? - no new 14C entering, but 14C is decreasing due to decay

  13. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) How long does it take for 14C to decay? - half life (t1/2) = 5,730 years - So every 5730 years, half the amount of 14C remains So if I die today, and a scientist find my bones 11,460 years from now, how much would you expect the 14C to have decreased? By 75% (cut in half twice) or there should be about 1/4 the atmospheric 14C

  14. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? Question: Your measurements indicate that a fossilized skull you unearthed has a 14C-to-12C ratio about one-sixteenth that of the atmosphere. What is the approximate age of the skull? 22,920 years old

  15. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? How do we determine the age of rocks and the fossils they contain? Radiometric dating - based on measurement of radioactive isotopes - Carbon-14 dating (14C) - Works well for fossils <50,000 years old (at this point most of the 14C has broken down) - For older fossils: Potassium-40 dating - t1/2 = half life = 1.3 billion years - Works well for rocks and fossils hundreds of millions of years old LIMITATION: error factor of +/- 10% for radiometric dating

  16. Chapter 15: Tracing Evolutionary History AIM: How do we determine the age of rocks and the fossils they contain? Review 1. Macroevolution - major changes over time 2. Geological Time Scale (GTS) - built with fossil evidence 3. Radiometric dating - allows scientists to determine the age of rocks and fossils for a more accurate GTS (absolute dating) 4. Relative dating - Dating using the relative position of the fossil you found to the other fossils above and below it in sedimentary rock. Ex. If I find a feathered dinosaur fossil, and below it I find a non-feathered dinosaur fossil, and above it I find a bird fossil, I can conclude that this feathered dinosaur is older than the bird, but younger than the non-feathered dino.

  17. Chapter 15: Tracing Evolutionary History NEW AIM: How do scientists (systematists) organize life? Phylogeny - the evolutionary history of a group of organisms

  18. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Phylogenetic tree (evolutionary tree) - diagram that traces evolutionary relationships as best we can

  19. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Systematics - the study of biological diversity in an evolutionary context - includes taxonomy (naming and classification of species) - grouping species into broader taxonomic categories Taxon - a taxonomic level (family, order, class, etc…)

  20. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Taxonomy follows phylogeny (evolutionary relationship)

  21. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Taxonomy follows phylogeny (evolutionary relationship) A major branch in the phylogenetic tree will be a major taxon like a class, order, family, etc…

  22. One species of domestic cat Many species of Carnivores Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Each taxonomic level gets more and more constrained in its definition until you only have a single species. Phylogenetic trees are Built using: - structural and developmental features - molecular data - behavioral traits

  23. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  24. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  25. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  26. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  27. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  28. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? How are divergent and convergent evolution different?

  29. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Divergent evolution: Occurs when a group from a population develops into a new species… The new species will microevolve independent of each other potentially leading to similar structures with different functions called… Homologous structures

  30. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Divergent evolution: Homologous structures PROBLEM: Not all likeness is inherited from a common ancestor

  31. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Example: Closer analysis of the DNA reveals that these leaves and spines are made in very different and unrelated ways… Ocotillo (Baja California) Allauidia (Madagascar) Structures that are similar, but not shared with a common ancestor (arose independently) are called analogous structures.

  32. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Example: Closer analysis of the DNA reveals that these leaves and spines are made in very different and unrelated ways… Ocotillo (Baja California) Allauidia (Madagascar) How do analogous structures come to exist in nature?

  33. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Convergent evolution: Different species may live in similar environments that naturally select for similar traits. Therefore, these species converge on similar traits from completely independent evolutionary events (there is no common ancestor with the trait). mice bats lizards birds Wings evolve Wings evolve Common reptilian ancestor without wings

  34. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Examples: The insect wing, pterodactyl wing, bird wing and bat wing are analogous structures. Why?

  35. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Examples: Because they do not share a winged common ancestor. The wings evolved independently in each case.

  36. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Examples: What about the bone structure of the pterodactyl, bird and bat wing?

  37. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Examples: **The bone structure of the bat wing and bird wing is homologous because the common ancestor of these two (reptiles) had a similar bone structure. However, the rest of the wing evolved independently. There is no winged common ancestor.

  38. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Examples: The structures of dolphins and fish are an incredible example of analogous structures. The recent ancestors of dolphins were land mammals. The fins and shape of these two groups of organisms evolved independent of each other…

  39. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Fig. 15.14A

  40. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Fig. 15.14A

  41. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life? Why do we think eukarya branched off archae and not eubacteria? Fig 15.14B

  42. Chapter 15: Tracing Evolutionary History AIM: How do scientists (systematists) organize life?

  43. NEW AIM: How did life begin on Earth? Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18 How did life begin on Earth?

  44. NEW AIM: How did life begin on Earth? Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18 The Nebular Hypothesis One of many hypothesis that attempts to describe the birth of our SOLAR SYSTEM. Initially, the mass of the solar system was spread out in a slowly rotating cloud of dust and debri called a nebula. The nebula would have formed as the result of a supernova – a violent explosion at the end of a large stars (8x bigger than our sun) life.

  45. NEW AIM: How did life begin on Earth? Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18 The Nebular Hypothesis The cloud would have collapsed due the force of gravity (attraction of all mass to all other mass) When a large, slowly rotating mass collapses inward, it becomes a small, fast rotating mass – (think of a spinning figure skater with their arms out. What happens when they pull them in? – the law of conservation of angular momentum) The rapid spinning would cause the mass to flatten like a disk (what happens when you throw pizza dough in the air and spin it?)

  46. NEW AIM: How did life begin on Earth? Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18 The Nebular Hypothesis The majority of the mass would still be in the center held by gravity forming the sun. The mass in the disc would begin to clump together (accretion) and form the planets.

  47. NEW AIM: How did life begin on Earth? Earth’s Beginning 4.6 Billion years ago 1. The great bombardment From 4.6 to 4 billion years ago the remaining mass in the vicinity of Earth was drawn in by Earth’s gravitational field. Earth was a molten ball of rock…

  48. NEW AIM: How did life begin on Earth? 2. Cooling Down The outer surface of the planet cooled off and solidified forming the crust (current land sea floor) There is no atmosphere yet. It is too hot; any gases would escape Earth’s gravitational field…

  49. NEW AIM: How did life begin on Earth? 3. Formation of the atmosphere How did the atmosphere form? A. First, the Earth needed to cool enough to hold an atmosphere… B. The atmosphere was generated by gases blowing out through the Earth’s crust…we call these… Volcanoes C. What was the early atmosphere composed of and how did you come up with this?

  50. NEW AIM: How did life begin on Earth? 3. Formation of the atmosphere D. We hypothesize that the gases emitted by volcanoes 4 billion years ago was similar to what they continue to emit today: - Carbon monoxide (CO) - Carbon Dioxide (CO2) -Nitrogen (N2) - Water H2O - Methane (CH4) - Ammonia (NH3) - Hydrogen (H2) (This is your early atmosphere) We still do not have any liquid water…no oceans…why? Too hot, all water is in the gaseous form…the oceans are in the atmosphere

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