Unit 2 Lecture Notes - History of the Earth PDF

Sci 1260--Unit 2 *History of the Earth* I. Thursday (life, exoplanets, collisions) a. Bring: lecture notes, laptop, roll b. Before class: i. Set up all youtube clips 1. Cosmic eye at 1:33: 2. Spinning balloon in slo-mo at 1:07: 3. Formation of Earth I (connects to Unit 1): 4. Formation of Earth II at 1:51 (collisions, moon): 5. Formation of Oceans at 1:02: ii. Set up PollEverywhere iii. Set up coursepack to p. 23-24 iv. Optional videos: 3min "cosmic eye" , 2min of famous SETI sounds from space (), then 2min SETI song: c. Announcements v. Review due dates (see powerpoint slide) vi. Discuss P-finalize; share your ideas with group members, and call me over if you'd like to discuss vii. E1 will be returned at end of our next class (one student got sick and still needs to take E1) II. Intro to the Earth -- who cares? d. Intro to today's topics: Space is immense and mostly unknown viii. Context: show 30s video clip of 1:33-2:00 within (zoom in from supercluster of galaxies to a woman's eye...probably watch this clip 2X, once for the 'wow' factor, then once for noticing deeper details) ix. Compute how much is out there beyond our little planet 6. \# of stars in our galaxy = \~100 billion (1 with 11 zeros) 7. \# galaxies = \~100 billion (1 with 11 zeros) 8. Write out total \# of stars and point out that each used to be a nebula (i.e., a nondescript clump of hydrogen gas) x. PollEverywhere open-ended: If you could know just one thing about the rest of space, what would it be? (probably whether ET life exists and then to characterize it) e. What makes the Earth interesting from a non-Earth perspective? (LIFE) f. Today's topics: what is life?, exoplanets, formation of the Earth (collisions) g. What would it be like for humans to discover life beyond the Earth? xi. The greatest discovery never made...yet. Thought questions: How would discovering intelligent life outside of the Earth shake up the discipline of business? Communications? international relations? Biology? xii. 3min video clip showing how society might respond to the discovery of intelligent life outside of the Earth: [http://www.youtube.com/watch?v=rYzc\_H9cgqM](http://www.youtube.com/watch?v=rYzc_H9cgqMf) (Context: movie = *Contact*, first video signal received from the aliens was a copy of the earliest video signal ever broadcast from Earth into space, which just happened to be the opening of the 1936 Olympic games under Nazi Germany) xiii. If we must visit then we are unlikely to discover extra-terrestrial life in your lifetime, because space is immense and rocket ships go only so fast (max so far \~50,000mph) 9. Even if we could go the speed of life (670 million mph) then it would take 4yrs to visit the closest star outside our solar system (Alpha Centauri) 10. Most likely place to find life near Earth? (moon: no evidence, Mars: no evidence yet. Neal deGrasse Tyson thinks our best bet for finding life is the oceans of Europa, a moon of Jupiter that has probably experienced liquid oceans for over a billion years) xiv. Another possibility is to listen to radio signals coming from outer space 11. All human communications through radio, TV, the internet, etc. travel through the air and into space at the speed of life 12. SETI (Search for Extra-Terrestrial Intelligence) analyzes incoming radio waves for intelligent signals 13. From the scientist's perspective: 4min clip showing first contact: (4min, start at 0:33): a. More context from movie: in addition to the obvious prime number signal, the aliens also sent back the first video signal ever broadcast from Earth into space, which just happened to be the opening of the 1936 Olympic games under Nazi Germany b. From society's perspective: 3min clip showing how society responds: h. (If needed, shorten to amino acids and nucleotides) What is life? (2min group contest, +1 if correct, -1 if incorrect, 0 if blank): distinguish reality from myth (p.23) (students should know whether a given trait defines life on Earth, and they should understand caveat that life is defined based on N=1) i. How common is life in the universe? xv. No one has a good answer, e.g., scientists say N=1, poets dream big, critics say scientists haven't looked very far yet, e.g., core samples collected from Mars river delta in Fall '22 probably contain organic compounds and will return to Earth in 2033 or later ([Nature article](https://www.nature.com/articles/d41586-022-02968-2)) xvi. Drake equation provides a framework for how to think about the discovery of extra-terrestrial life, and we've made major progress during student lifetimes on one of the key terms of the equation j. (probably skip) 3min group research task: Go online and research one of the FOUR terms listed at the bottom of p.23. Be prepared to explain the term to the class and its relevance to the search for extraterrestrial life. xvii. Goldilocks Zone = any object in space for which liquid water could potentially be found at the surface of the object xviii. Exoplanet = planet that orbits another star outside our solar system xix. Miller-Urey Experiment -- we'll cover at our next class when we discuss origin of life xx. Drake Equation -- be brief III. Intro to Exoplanets k. Connect the formation of exoplanets, distant stars, etc. to the nebulae and the clumpiness that existed after the Big Bang l. Only studied very recently: xxi. 1995: discovery of 1^st^ extrasolar planet orbiting a main-sequence star xxii. 2010 (when I started teaching SCI1260): 414 exoplanets discovered xxiii. Early 2016: \~2000 xxiv. Sep'23: \~5500 m. How do scientists detect them? (help video available on moodle) xxv. **Wobble method**: Star wobbles because of the planet's gravitational pull xxvi. **Transit method**: Planet passes in front of star (e.g., Kepler's discoveries) xxvii. These methods allow scientists to make inferences about the mass of the exoplanet and how close it is to its star 14. Distance btwn exoplanet and its star c. Closermore wobble (b/c of gravity) d. Closershorter orbitfrequent transits 15. Mass: e. More massmore wobble (b/c of gravity) f. more masslarger and therefore blocks out more starlight during a transit xxviii. Most exoplanets discovered so far are "Hot Jupiters" 16. Hotclose to the star 17. Jupiterlarge exoplanet 18. This almost certainly reflects a sampling bias g. the methods are more likely to sample Hot Jupiters than Cold Earths h. statistical estimates suggest smaller Earth-sized planets outnumber the larger exoplanets n. Connections to the search for life xxix. Habitable Zone (also called Goldilocks Zone) = any object in space for which liquid water could potentially be found at the surface of the object. 19. Determined by the following... i. Star characteristics + distance btwn planet: determines temperature (too cold = ice, too hot = water vapor) j. Size of planet -- determines pressure (too much pressure = ice, too little pressure = water vapor) 20. It's VERY difficult to detect actual liquid water, so Goldilocks Zone focuses just on where liquid water *might* be present 21. \~4 bya Mars was nearer the center of the Habitable Zone, and the Earth was on the edge (on the hot side) 22. Hidden assumption = life can originate only if liquid water is present k. N = 1 planet with life; that's a tiny sample size to make an inference about life everywhere in the universe l. Bryson quote: "a big part of the reason that Earth seems so miraculously accommodating is that we evolved to suit its conditions" xxx. Recent discoveries 23. Atomic emission spectra from light shining through the atmosphere of an exoplanet indicated the presence of water vapor and methane (Feb 2008) 24. Several exoplanets in the Goldilocks Zone have been found including an Earth-sized planet orbiting our nearest neighbor star (Proxima Centauri, Aug '16) 25. Using statistical methods scientists in Nov 2013 estimated up to 40 billion exoplanets in habitable zone within just the Milky Way galaxy, i.e., one for every \~10 stars xxxi. Best empirical tools moving forward... 26. Keep finding more exoplanets 27. Measure atomic emission spectra from those exoplanets (very difficult b/c planets don't give off light; scientists therefore depend on star light passing through the exoplanet's atmosphere -- assuming an atmosphere exists) 28. Visit nearby worlds, e.g., Mars, Europa, Titan, maybe Venus IV. Early formation of the solar system o. Connect story to the Big Bang and the previous class (WMAP data show Big Bang produced a universe with a clumpy distribution of matter clumps began to coalesce b/c of nebular hypoth, our solar system used to be a relatively small clump of matter that formed within the Milky Way galaxy) p. How long has our sun been burning? (Data = measure how much H remains and how much He has been produced then infer how far the Sun is in its lifespan. We infer sun is halfway through its lifespan) q. Basic storyline for the early solar system, i.e., what was going on \~4.5-5bya when the solar system was first forming? xxxii. **Rings of matter debris surrounding the Sun**: 29. When a nebula collapses it almost always spins on itself. What happens when you start spinning a ball of loose matter (like a nebula): show a few seconds starting at 1:07 of the slo-mo video of a spinning wet balloon () 30. Data: Review the current composition of the solar system; from this evidence we can reason that there must have been a large central clump of matter and a ring of debris around it; we have seen similar organization in other solar systems 31. Model: computer simulations show that motion of the matter due to gravity would result in collection of a ring of debris xxxiii. **Accretion of matter into clumps**: Based on our understanding of gravity, matter must have begun to coalesce to form the Sun and proto-planets 32. (Optional) Gee-whiz info: Mathematical patterns might exist on the distances of planets from their stars, possibly related to the "orbital resonances" of the electron shells within atoms. For example the seven TRAPPIST planets are at distances from their star with whole-number ratios, i.e., 1.51, 2.42, 4.04, 6.06, 9.1, 12.35 and ratios of 8/5, 5/3, 3/2, 3/2, 4/3. The mathematical regularity makes me think there might be a way to predict the existence of undiscovered exoplanets.. Someone even used these ratios to make planetary music, as explained in a 4min video clip: xxxiv. **Lots of collisions**: Based on the presence of craters on the moon and Mars we can infer lots of collisions, particularly as the matter first began to accumulate; what would be the effects of these kinds of collisions? 33. Collisions like these would generate enormous amounts of heat m. This heat would cause any liquid water to evaporate n. This heat would dissipate only slowly, and especially from the surfaces 34. Accumulation of matter, i.e., mass of planet would increase 35. Big collisions would change rotational speed, speed of our orbit around the Sun, and tilt; therefore our current daylength, yearlength, and seasons result from these early collisions 36. Really big collisions could cause large pieces of the proto-planets to break free, although gravity would pull most of it back down r. 3-min NatGeo youtube video: Formation of solar system and proto-Earth through the nebular hypoth: (good review and connects to Unit1) V. Formation of the Earth (**key mechanism of change = early collisions**) s. Summary so far xxxv. Btwn 4.5 and 5mya the solar system looked like Saturn 37. Central mass = Sun (protostarstar) 38. Disk of debris = Future planets and asteroids; gradual accretion of matter to form the planets xxxvi. After the Sun ignited, intense solar winds would have removed much of the smallest debris of the disk and would have blown away the early Earth's atmosphere (mostly H and He); therefore most the Earth's current atmosphere must have formed from gases that spewed out of the Earth itself, e.g., from volcanoes xxxvii. The early Earth (i.e., Hadeon eon, \~4.5-3.8bya) was dominated by collisions and meteors between the remaining material 39. Collisions likely affected all of the inner planets 40. Evidence = craters from meteors all over the moon that date to the Hadean Eon 41. Why are there so few visible craters on the Earth? (erosion) t. \~3.5min video segment from Miracle Planet I: , Start with beginning of Scene 2-Collisions (at 1:51 on youtube video), and end when narrator states that origin of life is "open to conjecture and debate"; (top of p. 24; follow video with group discussion, and then class discussion) xxxviii. What is the actual evidence that suggests a greater number of early inner planets, and what would have happened to these hypothetical planets? (evidence of craters shows the Earth must have experienced collisions, but the exact number of collisions is speculative) xxxix. What caused the Earth to increase in size? (with each collision the Earth would have gained matter) xl. As evidenced by geothermal vents and volcanoes, there is an enormous amount of heat below the Earth's crust. How did this heat originate? (mostly from the collisions, although there is also a lot of heat generated by the radiation emitted by radioisotopes) xli. How was the moon formed, and what evidence could we collect that would allow us to test this interpretation? (leading hypothesis = last major collision, followed by collection of debris from a ring that surrounded and orbited the Earth; for evidence see below) u. The nebular hypothesis model suggests that collisions would have resulted in... xlii. Earth gets larger 42. Why? b/c collisions bring together matter, and gravity glues it together 43. Significance? Eventually Earth's size is big enough that the amount of atmospheric pressure facilitates the presence of liquid water xliii. Earth's core stores up lots of geothermal heat 44. Why? b/c the objects colliding with Earth have lots of kinetic energy that can't disappear; the energy gets stored up deep inside the Earth as geothermal heat energy, which continues to dissipate today through volcanoes, deep sea ocean vents. (Caveat: about half of the Earth's heat also results from radioactive decay of radioisotopes inside the Earth) 45. Significance? The release of energy released at tectonic plate boundaries is what drives plate tectonic activity today. Smaller planets/moons also experienced collisions, which heated their cores, but b/c they were smaller the heat energy was lost and there is no longer tectonic activity on them xliv. The most recent huge collision likely resulted in the origin of the Earth's moon (as shown in the video). What is the evidence? 46. The elements on the moon are basically the same as those found on the Earth, e.g., similar composition of oxygen isotopes 47. Radiometric dating gives moon rocks a similar age to the Earth (\~4.4bya) VI. Key changes that made life possible; we assume life was not present on the early Earth (confirmed by the fact the earliest rocks in the fossil record show no evidence of life) v. Heat from the collisions escapes continually into space xlv. Eventually enough heat escapes from the surface that the **crust cools**, and the **water vapor condenses to fill the oceans** (2.5min video clip starting from 1:02: ); water originated in equal parts from two places 48. Volcanic activity: spews water vapor into the air 49. Comets from space: contain huge amounts of ice, which would have vaporized upon collision with the Earth xlvi. Heat loss means extensive **volcanic activity**; by looking at gases spewing out of modern volcanoes (and other evidence---chondrite meteors produce methane and ammonia), we can deduce **early atmosphere** of Earth w. Position, size, and motion of the Earth, which resulted from unpredictable collisions early in the Earth's history xlvii. Matching game (middle of p. 24) 50. Distance to Sun determines amt of heat from Sun (and thus whether liquid water will form) 51. Mass determines magnitude of gravity 52. Time to orbit the Sun determines yearlength 53. Time to rotate determines daylength 54. Tilt determines seasons; more extreme tilt would mean more extreme seasons xlviii. Speculate briefly on the potential effects of a different series of collisions x. Collisions gave the Earth its size, shape, the moon, daylength, yearlength, etc. (Course theme = everything from the present can be traced to the prehistoric past) VII. Tuesday (origin of life, timelines) (show up \~15min early) y. Before class xlix. Prep extra credit for E1; Adjusted scores would be up to median = 79.5% l. make sure students are submitting P-finalize, possibly email them several hours before class starts z. Pluto visits my 2:30pm section, then they talk with me about bioacoustics after class a. Bring: lecture notes, laptop, roll, graded exams, materials for timeline activity b. Materials for timeline activity li. \~22 pages blank paper per section lii. post-it notes labeled 4.5bya, 4bya, 3.5bya...1.5bya, 1bya, 900mya, 800mya, 700mya...100mya, 50mya, today c. Before class liii. Get out materials for eons and timeline activities (distribute to each group) 55. 100' measuring tape 56. Calculators 57. Rulers 58. Markers/colored pencils 59. Masking tape liv. Set up post-it notes set up around one wall of room: corner = today, 3ft = 500mya, 6ft = 1bya, 9ft = 1.5bya, 15ft = 2.5bya, 21ft = 3.5bya, 27ft = 4.5bya lv. Optional videos: 2min of famous SETI sounds from space (), then 2min SETI song: d. Announcements (see ppt) VIII. Review last class e. Collisions explain A LOT (see powerpoint slide). More review from Polleverywhere f. A scientist using the transit method announces the existence of a new exoplanet. Using her methods, you measure that the dip in light level occurs frequently -- about once every six days. What would you conclude based on your new measurement? lvi. The exoplanet has an atmospheric pressure like that of Earth (incorrect; atmospheric pressure would be the same only of the exoplanet's mass were similar to the Earth; the new data do not allow us to infer the size of the planet) lvii. The exoplanet is close to its star, i.e., a 'hot' exoplanet (yes; if an exoplanet is close to its star then it transits in front of the star frequently) lviii. The exoplanet is in the star's habitable zone (no; we have insufficient data to make that determination. Furthermore, most exoplanets close to their stars are too hot to have liquid water) lix. The exoplanet must be large, i.e., a 'Jupiter-like' exoplanet (no, the size of an exoplanet would be determined by how much light is blocked, i.e., a very large dip in the light level) g. T / F Scientists conclude that exoplanets are in the habitable zone only after confirming for the presence of water on the planet (no, habitable zone means that water, if present, would be in liquid form, because the temperature and pressure at the surface of that planet provide suitable conditions. It is rare for scientists to be able to make any conclusions about which molecules are present b/c exoplanets are dark) h. If the Earth had experienced one fewer massive collision during its formation, which of the following would describe the modern Earth? lx. Daylength would still be 24 hours (unlikely; each massive collision would have changed how long it takes for the Earth to do one rotation) lxi. Humans would weigh more (no; one fewer collision would mean less mass for the Earth, which would mean less gravity and we would all weigh less) lxii. Earth would not have any oceans (incorrect; we would still have liquid oceans, just with less water because much of the water came from the comets) lxiii. We would still experience volcanoes (yes; volcanoes happen because of all the heat below the surface of the Earth, and the heat results from the absorption of the kinetic energy brought from each of the collisions. Over billions of years the Earth's interior eventually cools completely, and plate tectonics stops. With one fewer collision there would be a little less heat, but there were still dozens of massive collisions, so we would still have plenty of heat to drive plate tectonics.) i. Which of the following statements about the early solar system is true? lxiv. Accretion of debris played a role in the formation of the Earth, but not in the formation of the moon (incorrect; accretion played a key role in the formation of both. The early solar system used to look like Saturn, and the Earth formed from accretion of debris in the Sun's 'ring.' The early Earth also used to look like Saturn, and the moon formed from accretion of debris in the Earth's 'ring.') lxv. Right after the worst collisions of the early Earth, the oceans did not exist in liquid form (correct; during the bombardment the Earth absorbed enormous amounts of heat, the surface of the Earth would have been boiling hot, and the oceans would have been gaseous water vapor forming a massive cloud that never rained until the Earth's surface finally cooled after the bombardment ceased) lxvi. The elements found on the surface of the moon are very similar to the elements found in the Earth's core (incorrect; the elements of the moon are similar to the elements of the *surface* of the Earth, but the Earth's core was mostly left intact during the bombardment, which meant the Earth has elements there that aren't found on the moon) lxvii. The early solar system had eight planets that correspond to the eight planets found in our solar system today (incorrect; the early solar system was more crowded than it is today; through accretion and massive collisions, the early 'planets' would collide with each other and fuse to form larger planets) j. What is the best evidence the Earth and other objects within the inner solar system experienced a lot of collisions? lxviii. Craters (the only good explanation for a crater is that something must have bombarded the surface, so when we measure craters everywhere on the surface of every planet/rock in our solar system we know there must have been a lot of collisions in the distant past) lxix. gravity (gravity explains the mechanism the caused collisions to happen, but it is a theoretical model, not something that was measured to prove collisions happened) lxx. nebular hypothesis (again, this is a theoretical model (featuring gravity), not something you could measure) lxxi. volcanoes (it's true that volcanoes happen because of the heat under the Earth's surface, which resulted from the kinetic energy delivered to the Earth by the collisions...but there are other possible explanations for how the Earth got so much heat under the surface. In other words, by itself volcanoes are only weak evidence for collisions) IX. (if time is short, skip directly to d: "Origin of life boils down to...") Transition to origin of life k. Story of creationist lecture I attended at CSU: title = "From Goo to you through the zoo" l. Starting with the "goo" seems a little daunting lxxii. for one thing, how do we know it was goo? lxxiii. Course theme = Truth in science must be based on observations (anything smaller than a cell can't fossilize, so we have zero record of the origin of life) m. Let's try going backwards. Take one of the carbon atoms in you right now -- where did it come from according to scientists? (draw flowchart on whiteboard) lxxiv. At some point in the past the carbon atom was part of the food you ate (plant -- part of an **organic molecule** such as a protein, a DNA molecule, etc.) lxxv. Where did the plant get that carbon atom? (CO2 in the air -- **inorganic molecule** in the nonliving environment) lxxvi. Ever since life began, the carbon atom **cycled** between organic and inorganic molecules, but if we go back far enough the record shows the same atoms, but all in inorganic form. lxxvii. To explain origin of life, our task is to explain the **inorganicorganic transition** n. Origin of life boils down to explaining the origin of nucleotides and amino acids, which are the building blocks of the most foundational organic molecules, DNA and proteins, respectively. X. Intro to the four eons of the Earth o. Introduce the names and timing of the eons on the geological timetable (p. 26) lxxviii. You will memorize most of p26 for the next exam lxxix. Today we focus on Hadean and Archean Eons p. timeline activity: groups work together on a math and 9" timeline problem: use calculators, math, and rulers; cover just the names of the eons for now (Hadean starts 4.5bya, Archean starts 3.8bya, Proterozoic starts 2.5bya, and Phanerozoic starts 542mya) q. (Save the eras and periods for later) XI. Review Formation of the Earth (Hadeon Eon) r. Collisions = major unifying principle s. After the major collisions ended, the Earth began to cool (\~4-3.8bya, but timing is uncertain) lxxx. Hadean transitioned to Archean Eon when collisions stopped, and the Earth cooled lxxxi. Oceans (and some limited land) formed; (2.5min video clip starting from 1:00: ) (listen for 'steam' Scottish accent, i.e., water in gaseous form); water originated in equal parts from two places 60. Volcanic activity: spews water vapor into the air 61. Comets from space: contain huge amounts of ice, which would have vaporized upon collision with the Earth t. Atmosphere formed as volcanoes spewed out gases lxxxii. Water vapor (clouds and rain would have happened after some cooling) lxxxiii. Carbon dioxide (CO~2~) and methane (CH~4~): life is built on carbon lxxxiv. Ammonia (NH~3~, over time became N~2~, which is \~80% of the modern atmosphere) lxxxv. Sulfur dioxide (SO~2~) (that's why major volcanic eruptions are often followed by short periods of global cooling) lxxxvi. Prominent features lacking from the atmosphere: Oxygen (O~2~) and ozone (O~3~) because no photosynthesis yet u. What would it be like for a modern human who landed on the early Earth at the end of the Hadean? lxxxvii. Very hot (because heat from collisions was still escaping) lxxxviii. Cloudy (because heat from collisions would have generated huge amounts of water vapor from the water transported to Earth via meteors/asteroids) lxxxix. Reddish tinged atmosphere (because of the methane) xc. No way to breathe (because no O~2~) xci. Skin cancer (because no O~3~) xcii. Lots of volcanic activity (because heat from collisions was still escaping) xciii. Lots of liquid water in the early oceans with only a few small pockets of land near the volcanoes (plate tectonics was just starting; most of the Earth's continental crust built up slowly through long periods of plate tectonic activity) XII. Origin of life in Archean Eon, i.e., how did nonliving matter become alive? (take home = two speculative hypoths) v. What do we really know about the origin of life? xciv. Life began in the liquid water (b/c every cell of every organism is mostly water; it is impossible for life to function today without water) xcv. Life began very simple (b/c earliest fossils were very tiny cells at 3.5bya) xcvi. It happened btwn 4 and 3.5 bya 62. Earth was not cooled sufficiently for liquid water until \~4bya (earliest hardened rocks were actually \~3.8bya based on radiometric dating) 63. fossil record shows no life until **stromatolites** (fossil proks) at 3.5bya w. What don't we know about the origin of life? xcvii. We have zero evidence of any early life smaller than a cell 64. Anything smaller than a cell would not fossilize 65. Our best hope of understanding is to find life on another planet (e.g., Mars, extrasolar planet, from a meteor) -- perhaps subcellular life xcviii. Video clips to introduce how life originated 66. 3min video clip of NdGT discussing Miller/Urey exp't (just show 13:43-16:43, end at "vital ingredients of all living things" plus newspaper): 67. 2.5min video clip of cartoon overview of the two hypotheses: (just show 0-2:18) xcix. Background -- at the molecular level what distinguishes living vs. nonliving matter 68. Scientists generally assume earliest "life" was organic molecules 69. What simple organic molecule is the most fundamental to all life o. Nucleotide = building block of all DNA (and RNA) p. Amino acid = building block of all proteins c. Review two mechanisms for how life might have begun on Earth 70. Panspermia hypothesis: q. Life originated on another planet r. organic molecules were transferred to a meteor/asteroid s. Meteor crashed into Earth, depositing organic molecules t. Simple molecules evolved to form more complex living substances 71. Primordial soup hypothesis: spontaneous generation of simple organic molecules u. postulated environmental conditions of the early Earth were adequate to spontaneously generate life when given sufficient energy and time v. Simple molecules evolved to form more complex living substances x. Evidence for Panspermia hypothesis ci. Organic materials sometimes found in meteorites cii. E.g., Murchison meteorite landed in Australia in 1969 containing 12% water and a mixture of 74 amino acids (organisms on Earth use just \~20 AAs); later meteorites were shown to have molecules that are precursors to nucleotides (nucleobases, i.e., nucleotides lacking the sugar/phosphate backbone) y. Evidence for spontaneous generation hypothesis: Miller and Urey's (1953) experiment ciii. Simple inorganic molecules (based on the gases spewing out of modern volcanoes) + water + electrical energy many types of amino acids (more than just the 20 we have) civ. Many subsequent experiments show that all major organic molecules could have formed spontaneously under certain conditions XIII. (shorten as needed to make space for art contest and handing back E1 -- we probably need 30+ min from start of art contest) Speculation connecting organic molecules to the origin of cells z. Reminder: no fossils of anything smaller than a cell a. Likely big events cv. Organic molecules that replicate cvi. Formation of a cell membrane surrounding molecules b. Origin of replicating organic molecules cvii. Problem: Which came first: DNA or proteins? 72. In all organisms today, DNA is the only replicating molecule, but it cannot replicate itself without the help of proteins 73. In all organisms today, proteins do the major work of the cell, but proteins cannot be synthesized without the help of DNA 74. I.e., DNA and proteins could not have existed without each other cviii. Possible solution: RNA preceded both DNA and proteins 75. RNA does work in the cell (like proteins), but it can also be replicated (like DNA) 76. If true, then origin of lifeRNA-dominated org'msDNA-dominated org'ms c. Origin of cells (relatively easy problem to overcome) cix. Analogy -- oil droplets in water cx. Lipids naturally form bubbles, which could have trapped organic molecules; organic molecules protected by a barrier would be favored by NS over "naked" molecules d. Students order the following (bottom of p. 24) cxi. Organic molecules that cannot replicate themselves cxii. Organic molecules that can replicate themselves cxiii. Lipid membrane surrounding clusters of organic molecules cxiv. Single-celled organisms cxv. Multicellular organisms cxvi. Millions of organisms e. Short history of life on Earth = In the beginning there were simple organic chemicals replicating organic molecules cells diversity of living organisms (currently millions of species) XIV. Timeline of all major events (p. 25) f. Our classroom is about to become a timeline (point out post-it notes on walls) cxvii. P. 25 in coursepack lists several of the most important events in the Earth's history 77. How do we get the data necessary to make this handout? (mostly from fossils) 78. How do we know these dates? (radiometric dating) cxviii. Our job is to illustrate the events on p.25 g. Activity cxix. Divide the 22 lettered events up for groups to decorate signs for each event listed on p. 25 cxx. Decorate signs; materials provided up front cxxi. Group 10pt assignment 79. 10pts for participating and positioning your events correctly, e.g., -1pt for positioning a sign at the incorrect time 80. Contest: each student votes for two favorite signs at tinyurl.com/sci1260-11 Winning group gets +2 on timeline art assignment, 2^nd^ place gets +1 h. Learning objectives, i.e., what might you be asked on an exam? cxxii. Know the order of events cxxiii. Be able to place an event at its approximate position on a timeline i. (shorten as needed) After students make the timeline, walk through the timeline as a class and tell the history of the Earth with lots of repetition cxxiv. Why couldn't life originate until after the Earth cooled? (no liquid water) cxxv. Who was the dominant life form at 4bya? 3bya? 2bya? Etc. (Emphasize that most of history belongs to single-celled organisms; the "exciting" stuff is all recent) cxxvi. Which organisms evolved photosynthesis, and what is its significance? 81. Cyanobacteria (proks, still around today) 82. Oxygen is a byproduct w. Toxic to most species back then x. Made possible the evolution of aerobic respiration, which provides \~15X as much energy as anaerobic respiration cxxvii. Where did the first multicellular organisms live? (in the ocean) cxxviii. From our perspective, why were each of the following events important? 83. Snowball Earth (750-570mya): land was covered entirely in very thick glaciers 84. High oxygen content in atmosphere (600mya): Multicellular animals like us need so much energy that we could not have survived on previous levels 85. Why did vertebrates have to be last to colonize land? (food = plants, inverts) cxxix. Dino questions 86. What taxa did not live with earliest dinos? (mammals, birds, or flowering plants) 87. On what continent did the earliest dinos live? (Pangaea) 88. Was Pangaea the earliest supercontinent? cxxx. How long have humans dominated the Earth? XV. Report on E1 j. What makes a good score distribution from an instructor's perspective? (both criteria were met) cxxxi. Some students do very well (indicates I'm teaching well enough that some students are learning the content very well) cxxxii. Variation between scores (reflects the variation in understanding that I typically observe between students) k. Score distribution (see ppt) cxxxiii. I posted your scores to moodle cxxxiv. If you failed the exam, I'd like to talk to you individually. Please drop by my office hours or set an appointment l. Attendance mattered quite a bit (explained 20% of the variation in exam scores) m. Possible reminder your score doesn't reflect who you are or your value, only how you happened to perform on one assignment in one of your many classes. Do your best to take it in stride, and to learn from it. I'm here to help anyone who needs it, and I've seen students improve remarkably from E1 to E2. I also never pass any judgment on a student based on s/he performs. n. Hand back the exams XVI. Thursday (early evolutionary innovations, Snowball Earth) o. Prep hw4 p. Before class: Set up video clips cxxxv. Origin of euks (2min): cxxxvi. Snowball Earth video: Miracle Planet II, start at \~1min with Statue of Liberty; end at \~8:20min when they show the white Earth (also found at ) cxxxvii. 3.5min video highlights mechanisms for cooling/warming Snowball Earth, esp w/ regard to GOE: q. Announcements (see powerpoint) cxxxviii. To help you memorize p.26, we will have a series of low-stakes quizzes; Quiz1 at beginning of next class 89. Four eons; know the names, order and approximate dates, events (see p.26) 90. Three eras in Phanerozoic Eon: just know names, order and approximate dates 91. Quizzes 2&3 on p.27 -- will be given in future class periods cxxxix. Today 92. Early evolutionary innovations: prok cells, photosynthesis, euk cells, multicellularity 93. Snowball Earth cxl. Show schedule of project presentations r. Review last class: first include reminders about the timeline activity cxli. Review Qs to discuss in groups (see ppt) cxlii. Where is the science in this list of events and dates? 94. How do we get the data necessary to make this handout? (mostly from fossils) 95. How do we know these dates? (radiometric dating) cxliii. Learning objectives, i.e., what might you be asked on an exam? 96. Know the order of events 97. Be able to place an event at its approximate position on a timeline, e.g., remind students on the wall where dinos went extinct (65mya = 15.6"), where the human and chimp lineages diverged (7mya = 1.7"), and where humans emerged as a species (200,000ya = 0.05" = 1/20^th^ of 1") XVII. Early evolutionary innovations after life originated in the early Archean Eon (students fill out blanks on the bottom of p28 as I teach the content) XVIII. Evolution of simple cells (prokaryotes), a major innovation of the Archean Eon s. What happened? DNA no longer "naked" -- now surrounded by a cell membrane made of lipids t. Evidence = **Stromatolites** = layers of sediments accumulated by prokaryotes; we still see stromatolites forming today, and the earliest fossils are stromatolites dating to 3.5bya u. Why would NS favor? Protection for DNA and other organic molecules XIX. Evolution of **photosynthesis** by **cyanobacteria**, a major innovation of the late Archean Eon (2.7bya) v. Context: All organisms need energy cxliv. Earliest organisms would have obtained their energy from chemicals or geothermal heat, e.g., from a deep sea vent or volcanic fissure cxlv. Largest source of energy by far on Planet Earth = solar energy (especially on land) 98....so it's not surprising organisms evolved the ability to harness light energy 99. Currently, that's what powers the vast majority of organisms on Earth, although a few primitive aquatic prokaryotes still use geothermal/chemical energy. (Theme throughout Unit 2 = Life diversifies) w. What happened? Cyanobacteria evolved the ability to convert light energy + inorganic molecules into food cxlvi. Photosynthesis equation 100. Input = CO~2~ (present from atmosphere) and H~2~O (present throughout ocean), light energy 101. Output = sugar (food), and O~2~ (waste) cxlvii. Led to Great Oxygenation Event 102. Oxygen would have been toxic and almost certainly led to a mass extinction event (though fossil record of that time period is too scant to assess either way) 103. Several hundred years later **proteobacteria** evolved aerobic respiration, which allowed these organisms to get 18X as much ATP energy from their food (Future years: make aerobic respiration into a 5^th^ 'early evolutionary innovation' and modify p28, p29, and p26. Maybe streamline all five innovations) x. Evidence for photosynthesis (2.7 bya) cxlviii. Banded iron deposits: Ocean rocks containing iron with that date start to show rust (rust occurs only if oxygen is present) cxlix. Fossils similar to modern **cyanobacteria** with that date cl. The stripes probably indicate that cyanobacteria populations fluctuated dramatically over evolutionary time, likely because the oxygen was toxic to the cyanobacteria that produced them. Rust was produced only when cyanobacteria were present to produce O2 104. In other words, the cyanobacteria were killed by their own waste product 105. Eventually random genetic mutations produced enzymes within cyanobacteria that could cope with oxygen and neutralize its toxicity. At that point oxygen began to accumulate without limit, eventually oxygenating the Earth's atmosphere y. Why would NS favor? (b/c solar energy is so massively abundant) XX. Eukaryotes evolved from proks through **endosymbiosis** (major innovation of Proterozoic, 2.1bya) z. What happened? cli. Define eukaryote 106. large cell with membrane-bound organelles + nucleus containing several long linear chromosomes 107. Examples = plants, animals, fungi, and protists 108. Originally, all euks would have been single-celled protists, until multicellularity evolved within some euk lineages clii. Eukaryotes originated just once, because all euks form a monophyletic group (see "THE tree of life" on p. 34) cliii. Key event = endosymbiosis: Big prok cell "swallows" small prok cells 109. Small prok cell \#1 = proteobacteria y. After getting swallowed, proteobacteria became the mitochondria that are now found in all euks z. Proteobacteria are special b/c they can use oxygen to produce 18X as much energy (**aerobic respiration**) 110. Small prok cell \#2 = cyanobacteria a. After getting swallowed, cyanobacteria became the chloroplasts found in plants and many protists (algae) b. Cyanobacteria are special b/c they can make their own food from highly-abundant sunlight energy a. Evidence: cliv. DNA of mitochondria and c-plast more similar to bacteria DNA clv. Double membrane around nucleus, mitochondria and c-plasts b. Why would NS favor? Benefits of division of labor (we'll see this theme again in Unit 3) clvi. The swallowed cells (mitochondria and chloroplasts) become highly specialized to focus on producing energy/food, and they no longer have to worry about protection clvii. The larger cells no longer have to worry about making energy/food, so they can focus on other tasks XXI. Multicellularity evolved multiple times, but only within euks (also Proterozoic, 1.2bya) c. What happened? clviii. Multicellular = many cells stuck together clix. Evolved multiple times 111. Animals (mechanism = collagen holds cells together) 112. Plants 113. Fungi 114. Many protists, e.g., seaweed, volvox, slime mold d. Evidence = Fossils of early multicellular organisms e. Why would NS favor? Benefits of division of labor; cells can now specialize, e.g., brain cells, liver cells, kidney cells, reproductive cells XXII. Fill in the blanks in the table at the bottom of p.28 (what happened, when (eon), what evidence, why NS favors); answer key at top of p.29 XXIII. Today's big event = Snowball Earth f. : 8min video segment from Miracle Planet: start with Statue of Liberty, and end with picture of rotating white Earth; after video student groups discuss the following (bottom of p. 29): clx. Explain the origin of the "erratic" rock in Central Park clxi. Glacial deposits were found at many geographic locations 2.2 bya. Create a timeline of the history of the Earth, and then position 2.2 bya on the timeline. clxii. How did the scientists determine that the glacial rock was located at 11 degrees latitude? g. The entire Earth is frozen for tens of millions of years at a time, followed very quickly by a greenhouse-heated HOT planet clxiii. According to reading this happened up to four times btwn 750-580 mya, i.e., the late Proterozoic Eon clxiv. 1km of ice covers oceans at the coldest clxv. Average temp = -50 degrees Celsius followed by +50 degrees Celsius just a few thousand years later; comparable to all the global warming of the last century X \~100! h. The reality of Snowball Earth is not disputed by scientists, though some parts are still controversial, e.g., exact dates, extent of the ice, existence of refugia, whether Snowball Earth caused Cambrian explosion i. Key mechanisms to understand: clxvi. Balancing (Negative) vs. reinforcing (positive) feedback 115. Initial change to a system feedback from other parts of the system system responds to the feedback c. Balancing/Negative feedback = **resists changes** so that **system returns to equilibrium** (e.g., low blood sugar triggers hunger, high blood sugar triggers satiation) d. Reinforcing/Positive feedback = **amplifies changes** so that **system gets even further out of equilibrium**, **always destabilizing** (e.g., population explosion of rabbits) 116. demonstrate with various student behaviors, e.g., temperature regulation, escalation of a conflict or of a complimenting duel clxvii. How global temperature is determined: Draw flow of heat on whiteboard: incoming solar radiation -- reflection of heat + extra heat from greenhouse effect 117. Reflection of heat depends on albedo, which depends on color e. High albedo = light colors absorbs less heat, reflects more (e.g., white glaciers) f. Low albedo = dark colors absorbs more, reflects more (e.g., blue seawater) g. What would happen if we spray-painted all the land white? 118. Greenhouse effect h. Examples of greenhouse gases: Carbon dioxide (CO2), Methane (CH4), Water vapor (H2O), and more i. Without the greenhouse effect the Earth would be below freezing all the time j. What would happen to global temperature if we increased CO2 concentrations? j. Mechanisms leading to Snowball Earth (explained well in your reading -- a good way to review mechanisms -- make sure you understand at a deep level) clxviii. The freeze 119. No one knows why cooling started; we guess that greenhouse gas levels lowered 120. With initial cooling glaciers started to buildup. 121. White glaciers reflected heat back to space---reinforcing feedback for more global cooling 122. Eventually glaciation reached a threshold where the reinforcing feedback from high albedo overwhelmed other feedback mechanisms, the glaciers grew all the way from the poles into the tropics, and the entire Earth froze over 123. Glaciers continue to reflect away heat, and the Earth is stuck in a frozen state for up to 200 my (no rain, no water vapor, no clouds) clxix. The meltdown 124. Earth's interior is still hot, and volcanoes regularly belch out CO2 (b/c of collisions during Hadean Eon and radioactive decay of the radioisotopes in the interior) k. Normally the extra CO2 is slowly leached out of the atmosphere by rain, and/or absorbed by the ocean, and/or absorbed by living organisms (photosynthesis), but on a frozen Earth with no liquid oceans and mostly devoid of life, the extra CO2 just accumulates l. CO2 probably increased \>300X present levels, i.e., to \~13% of the atmosphere (for perspective, current global warming is caused by 0.028% 0.041%) 125. Eventually the heating from the greenhouse effect overcame the cooling from high albedo, and the Earth began to melt 126. Two reinforcing feedback mechanisms made global warming accelerate m. Melting glaciers increased amt of water vapor (a GHG), which intensified the warming from the greenhouse effect n. As glaciers melted, albedo effect decreased dramatically, so Earth absorbed even more incoming solar radiation 127. Climate models suggest -50 deg C to + 50 deg C in just a few thousand years o. -50 deg C = coldest temperature ever recorded in Barrow, AK p. 50 deg C = hottest temperature ever recorded in Phoenix, AZ k. Summarize the evidence for Snowball Earth clxx. Erratic rocks dated \~800-600 mya with magnetite orientation *(inference = global glaciation, erratics indicates glacier activity, magnetite orientation indicated low latitude meaning the rocks carried by glaciers were found near the equator -- glaciers could exist at the equator only if the whole Earth was in a Snowball Earth state)* clxxi. Carbon isotope ratio very low from \~800-600mya *(inference = mostly devoid of life, extremely low biological productivity)* 128. It makes sense that Snowball Earth would have triggered a mass extinction event 129. Aquatic life preferentially absorbs C-12 over C-13, so normally the C-12-to-C-13 ratio is very low; during Snowball Earth the C-12-to-C-13 ratio was very high, so there must have been very little aquatic life clxxii. Rock layers dated a little more than 600mya contain carbonate *(inference = very high atmospheric CO~2~, evidence for the thawing mechanism we already covered)* 130. Form of carbonate within rocks = calcium carbonate and magnesium carbonate 131. carbonate comes from excessive CO2 in the atmosphere; once rain begins again the CO2 finally starts to leach out of the atmosphere where it gets into rocks l. What remains controversial about Snowball Earth? clxxiii. exact dates (there were probably at least two Snowball Earths -- one near the beginning of the Proterozoic, one near the end of the Proterozoic, possibly others) clxxiv. extent of the ice (equatorial slush?) and possible refugia (marginal habitat in which life clings to a meager existence) clxxv. relationship of Snowball Earth to Cambrian explosion m. Review/Preview video clip clxxvi. 3.5min video that highlights mechanisms for cooling and warming Snowball Earth -- especially regarding GOE: clxxvii. Explain why scientists think the Great Oxygenation Event may have triggered the first Snowball Earth episode 132. Cyanobacteria evolve photosynthesis and begin to produce oxygen (O2) 133. Oxygen interacts with methane (CH4), a highly potent GHG 134. CH4 + O2 CO2 traps just 1/20^th^ as much heat (led to global cooling) XXIV. Terms to review this week (matching game on p.28, review answers as a class) n. Amino acids = simple organic molecules, building blocks of proteins (found on Murchison meteorite, and produced in the Miller-Urey experiment) o. Banded iron deposits = proof of the origin of photosynthesis 2.7bya p. Cambrian Explosion = origin of most animal groups 540mya (data = diverse fossils of the Burgess Shale) q. Cyanobacteria = first organisms to do photosynthesis, which produces oxygen as a byproduct r. Eukaryote = complex type of cell, e.g., human cells s. Lipid = main component of cell membrane, which surrounds all types of cells t. Murchison Meteorite = contained water and \>70 types of amino acids u. Nucleotides = simple organic molecules, building blocks of RNA and DNA v. Prokaryote = simple type of cell, e.g., bacteria w. RNA = molecule that replicates like DNA and acts as a cellular machine (enzyme) like a protein x. Stromatolites = earliest fossilized bacteria, dates to 3.5bya XXV. Review class (review answers as a class) y. Draw a 4.5by timeline with eons highlighted, then position origins of prokaryotes, photosynthesis, eukaryotes, multicellularity, and Snowball Earth episodes; list evidence for each event z. Identify: albedo, carbon isotope ratio, carbonates, erratic, greenhouse effect a. How did reinforcing feedback play a role in changing the climate both before and after a Snowball Earth episode? (hints: albedo, greenhouse effect) XXVI. Tuesday (oxygen, paleogeography, fossil fuels) b. Bring: lecture notes, laptop, roll, team Eons & Eras quizzes c. Before class: clxxviii. Get blocks of styrofoam from storage clxxix. Prep lots of YouTube videos and googleform survey titled "Quick Survey" () clxxx. Show 2min Ice Age video of continental movements: d. Review answers to hw4 e. Announcements (see powerpoint) f. Eons & eras quiz taken as groups (show ppt images) (review answers afterwards) g. Groups review Snowball Earth clxxxi. Mechanisms: Propose two possible solutions to modern global warming using model of global temperature clxxxii. Match evidence to inference 135. Rock dated to 0.25mya contains an Erratic Ice Age glaciation 136. Orientation angle of magnetite within rock used to be located at a specific latitude 137. High carbonate levels in rocks dated to end of Snowball EarthCO2 levels were high at that time period 138. Altered C-isotopic signature within rocks dated to Snowball Earth periodvery low biological productivity / likely mass extinction clxxxiii. Fill in blanks for a story of reinforcing feedback: Temperature increases slightlySnowball Earth starts to [thaw]solid water becomes [water vapor] in atmosphere[Greenhouse] effect enhancedtemperature [increases] even more clxxxiv. 12:30 section only: 3.5min video that highlights mechanisms for cooling and warming Snowball Earth -- especially regarding GOE: XXVII. Transition to GOE: making the Earth habitable for humans h. What would it be like for humans if we could land during the early Archean Eon soon after the Earth had cooled? Work with your group to explain each of the following: clxxxv. Very hot (because heat from collisions was still escaping) clxxxvi. Cloudy (because heat from collisions would have generated huge amounts of water vapor from the water transported to Earth via meteors/asteroids, water vapor also came from volcanoes that occurred because heat from collisions was still escaping) clxxxvii. Reddish tinged atmosphere (because of the methane from volcanoes...because of collisions) clxxxviii. No way to breathe (because no O~2~ because no photosynthesis yet) clxxxix. Skin cancer (because no O~3~...because no O~2~...because no photosynthesis yet) cxc. Lots of volcanic activity (because heat from collisions was still escaping) cxci. Lots of liquid water in the early oceans with small pockets of land near the volcanoes (most of the Earth's continental crust built up slowly through long periods of plate tectonic activity) i. What do humans need? cxcii. breathable air cxciii. protection from harmful UV rays cxciv. energy (fossil fuel) cxcv. blue sky (not red sky from the methane) cxcvi. What facilitated all the above? (oxygen!) XXVIII. Great Oxygenation Event (\~2.4bya = beginning of Proterozoic) j. Breathable air results from atmospheric oxygen (O~2~) cxcvii. Where did the oxygen come from? (**photosynthesis**, which had recently evolved in **cyanobacteria**) (see if students remember PS equation) cxcviii. How did other organisms respond to the oxygen? (no direct fossil evidence, but we know oxygen is toxic to organisms that never live around oxygen; therefore GOE likely resulted in a mass extinction) cxcix. Today oxygen level is \~20% of the air we breathe, but right after GOE oxygen level was \~1% cc. After GOE oxygen levels fluctuated over evolutionary time, which played a key role in the evolution of life and the formation of fossil fuel (stay tuned for later in this lecture) k. Protection from UV results from ozone (O~3~), which resulted from the presence of oxygen (O~2~) cci. More ozone would protect marine organisms from harmful sunlight UV, thus favoring even more photosynthesis, thus building up even more O2, thus building up more ozone (what kind of feedback loop is this? ***Reinforcing feedback loop***) l. Energy reserves results from the evolution of aerobic respiration ccii. All cells need ATP energy, which can be synthesized anaerobically (without O~2~) or aerobically (with O~2~). cciii. The major advantage of aerobic over anaerobic respiration is that aerobic results in 18X as much ATP energy per molecule of glucose cciv. Prior to GOE all organisms would have had to be anaerobic; for these organisms the GOE was all bad (probable mass extinction event) ccv. For the organisms in which aerobic respiration evolved (bacteria ancestors of our mitochondria), the oxygen in the air suddenly became a great boon (18X as much ATP!), and these organisms became wildly successful ccvi. Over evolutionary time the amount of biomass that could be supported has always depended on how much atmospheric oxygen was present 139. For \>1by oxygen levels remained low from our perspective (\~1% of atmosphere) 140. Big spike right after the most recent Snowball Earth (coincides with Cambrian Explosion) 141. Big spike in late Paleozoic (coincides with giant amphibians and Carboniferous forests) 142. Big spike in Mesozoic (coincides with large reptiles, e.g,. dinosaurs, pterosaurs) m. Blue sky results from the loss of methane (CH~4~) ccvii. Mechanism: CH~4~ reacts in the presence of O~2~ to form CO~2~ ccviii. CH~4~ and CO~2~ are both greenhouse gases, but CO~2~ is only 1/20^th^ as potent a GHG. 143. Therefore the loss of methane from the atmosphere would have also resulted in Greenhouse gases trapping much less heatmassive global cooling. 144. Because GOE dates to immediately before Snowball Earth I, we think loss of methane also triggered the first global glaciation ccix. Review why scientists think the Great Oxygenation Event likely triggered the first Snowball Earth episode 145. Cyanobacteria evolve photosynthesis and begin to produce oxygen (O2) 146. Oxygen interacts with methane (CH4), a highly potent GHG 147. CH4 + O2 CO2 traps just 1/20^th^ as much heat (led to global cooling) n. Diagram for students to review o. Qs for students to review ccx. The buildup of ozone resulted in which of the following? 148. Global cooling 149. Large body size 150. More ATP for cells 151. UV protection ccxi. Which of the following is NOT a component of the explanation for large reptiles during the Mesozoic Era? 152. Methane reacted with oxygen to form CO~2~ 153. Oxygen levels spike during Jurassic Period 154. Origin of aerobic respiration 155. Photosynthesis generates O~2~ as waste product XXIX. Transition: Rest of Unit 2 focuses mostly on Phanerozoic Eon p. Geological history (today) ccxii. Paleogeography: key mechanism = plate tectonics ccxiii. Formation of key natural resources: key mechanisms = role of oxygen and latitude q. Biological history (next 3wks) ccxiv. Intro to biodiversity and THE tree of life (integrate with timeline and geologic time scale) ccxv. Overview of Phanerozoic: biodiversity increases with periodic mass extinctions ccxvi. Paleozoic Era 156. Cambrian explosion -- origin of animals 157. Habitat transitions: waterland, landair, landwater ccxvii. Mesozoic Era: Age of reptiles -- dinosaur diversity ccxviii. Early Cenozoic Era? XXX. Overview of Plate Tectonics (Ch. 12 in Bryson) r. Background principles and mechanisms ccxix. Crust = relatively thin outer layer of the Earth, divided into several **tectonic plates**, each of which moves in a different direction and at a different speed (\~1-25cm/year -- similar to speed of fingernail growth) ccxx. Oceanic crust = thin and dense; continental crust = thick and less dense; (Styrofoam and phone demo) what would happen if oceanic and continental crust collided? 158. Which plate is more likely to sink and why? (oceanic b/c it's denser; plate sinking is called **subduction)** 159. What will happen to the temperature of a plate as it subducts, and why? (increases temperature b/c of all the geothermal heat stored up within the Earth -- due to those collisions. The subducting plate melts, which generates **magma**) 160. During subduction, what would happen to the edge of the continental plate and why? (continental gets pushed up b/c it's less dense, i.e., **mountains** that are also **volcanic** b/c of the magma) ccxxi. Students fill out top half of p. 31: convergent boundary diagram 161. Students should label oceanic plate, continental plate, subduction, and mountain formation, volcano formation 162. Oceanic plate is always denser than continental plate, so oceanic subducts and continental pushes up 163. 15s web demo of O/C convergent boundary at 164. C/C convergent boundary: mountain formation without subduction (and therefore no volcanoes either) s. Plate movements explain mountain ranges: Look at a map of the world's mountain ranges ccxxii. What kind of boundary is at the Himalayas, and how do you know? ccxxiii. What kind of boundary is at the Andes, and how do you know? t. Today we measure plate movements in real time with precision GPS equipment, but these data don't help us to reconstruct hundreds of millions of years of history u. How do we reconstruct paleogeography? What evidence do we use? ccxxiv. **What was connected?** Fossils/rock formations and related organisms often match up across oceans, which allows us to infer what landmasses used to be connected (e.g., Wegener's data) 165. E.g., crust near the outer banks best matches crust in NW Africa (near Morocco) 166. E.g., marsupials found primarily in Australia, and sometimes other southern continents ccxxv. **When connected?** Radiometric dating of the appropriate fossils tells us when these landmasses were connected to each other ccxxvi. **Where?** We can then infer the latitude at which these connected landmasses were located by collecting the following data: 167. paleomagnetic record (remember Snowball Earth video) 168. type of fossils (e.g., tropical plants differ from plants growing in polar region) XXXI. Example of using evidence to infer paleogeography: formation of Appalachians v. *What was connected?* Common rock formations of the Appalachians are also found in the Scottish Highlands, Norwegian fjords, and Little Atlas mountains of Morocco (therefore we infer these landmasses were connected) w. *When was it connected?* Radiometric dating of rocks reveals that the Appalachians are much older (\~400mya) ccxxvii. For hundreds of millions of years since their formation, the Appalachians have been eroding away because of water and wind; that's why Appalachians are so much smaller than Himalayas/Andes/Alps ccxxviii. \~400mya predates formation of Pangaea; Western Carolina used to be at the edge of the continent next to an oceanic plate that collided and subducted beneath the continent x. *Where?* Evidence from fossils and paleomagnetism puts us around the equator XXXII. Animations of paleogeography (lots of speculation prior to Pangaea) y. NatGeo: ; just show 1:09 through 3min, then ask the following questions (p. 31) ccxxix. T / F The Earth has experienced only one supercontinent. ccxxx. What was the name of the most recent supercontinent? ccxxxi. When the most recent supercontinent broke up, did it split north and south, or east and west? z. Answer last question on p. 31 (ordering paleogeographic events) using 4.5min video clip: (3.3by history); emphasize following stories: ccxxxii. Earth began with almost no land, but land built up over time (b/c of plate tectonics, which started right after the collisions ended near the end of the Hadean Eon ccxxxiii. Series of supercontinents throughout the Archean and Proterozoic Eons, e.g., Rodinia, Pannotia ccxxxiv. End of Snowball Earth was still long before Pangaea ccxxxv. Where were the Appalachians when they started to form during the Devonian Period (Paleozoic Era, Phanerozoic Eon)? (southern hemisphere near equator) 169. show geographic context 170. point out that verts were first walking on land around the same time ccxxxvi. Pangaea split into northern Laurasia and southern Gondwana 171. which of the two stayed together longer? 172. Dinos started to dominate during Pangaea, and they continued to dominate until the continents appeared quite similar to today ccxxxvii. Australia has been isolated since the Cretaceous Period (late Mesozoic Era) (long-term geographic isolation resulted in Australia having a lot of unique species) ccxxxviii. Himalayas and Alps did not start forming until the Paleogene Period (early Cenozoic Era) a. Possibly review paleogeographic movements of the entire Phanerozoic Eon in 15s: XXXIII. Transition to fossil fuels b. Industrial Revolution is one of the biggest historical forces that shaped the modern world ccxxxix. Focused on replacing human labor with machine labor, e.g., cotton gin instead of slaves, transportation vehicles instead of walking ccxl. What fueled the Industrial Revolution? Fossil fuels (coal, oil, and natural gas) c. Modern society still depends heavily on affordable and convenient access to energy. Quick survey: which three energy sources do we rely on the most NOW? (tinyurl.com/sci1260-1) ccxli. Lots of new energy technology, but we're still 86% fossil fuel ccxlii. Some of the biggest global conflicts take place over fossil fuel, e.g., natural gas from Russia, oil in Middle East d. We want to answer the question, "Why do some geographic regions have so much more fossil fuel than other regions?" XXXIV. How to explain the geographic distribution of fossil fuel e. What is fossil fuel? ccxliii. pressurized remains of organisms that died millions of years ago ccxliv. Geographic regions with the most fossil fuel today will therefore be the locations that used the have the most biomass f. Amt of biomass depends on water availability, which depends primarily on latitude ccxlv. Green portions of satellite map of Earth show that rainfall is concentrated in tropical regions, and to a lesser extent in upper temperate regions like Alaska/Siberia (also show rainfall map) ccxlvi. Because tectonic plates have been constantly moving for hundreds of millions of years, the regions with lots of water have it because they are fortunate enough to be at the right latitude right now 173. E.g., the region that we now call the Sahara Desert used to be a tropical forest during most of the Mesozoic, because Africa was farther south back then 174. Caveat: although latitude is the most important factor, other regional factors matter, e.g., ocean currents, topography g. Which group produces more biomass---plants or animals---and why? ccxlvii. Plants because they are the base of the food chain ccxlviii. Therefore fossil fuels are made mostly of plants and algae, and only trace amts of animals such as dinosaurs ccxlix. Coal () 175. Produced mostly from land plants (basis of terrestrial food chain) 176. produced mainly during the first spike of oxygen; hence the name 'Carboniferous Period' ccl. Oil/gas () 177. produced mostly from aquatic organisms at the basis of the marine food chain, such as algae and plankton 178. produced during both oxygen spikes h. Amt of fossil fuel that builds up depends primarily on how much biomass is produced, which depends on... ccli. How much rainfall (tropical regions get the most) cclii. How much oxygen (b/c more oxygenmore aerobic respirationmore energy for making biomass) ccliii. Two spikes in atmospheric oxygen 179. 1^st^ spike in oxygen: Carboniferous and Permian periods (\~359-251mya, especially Carboniferous Period) q. Giant insects, e.g., dragonfly with 2m wingspan, Also some giant amphibians r. What was at the equator during this time period? (Appalachiagiant Carboniferous forestscoal) 180. 2^nd^ spike in oxygen: Jurassic and Cretaceous (\~200 - 65mya) s. Giant dinosaurs, e.g., Apatosaurus, T rex t. What was at the equator during this time period? (Middle East was a shallow sealots of algae/planktonoil and gas) i. Piecing together the modern story ccliv. Trace the flow of energy 181. Original source of energy in fossil fuel = sun shines tens of millions of years ago 182. Photosynthesis converts sunlight energy into biomass: land plants (coal) and algae/plankton (oil/gas) 183. Biomass pressurized over time 184. Nonrenewablefossil fuels take tens of millions of years to form cclv. Where do we normally find coal? (on land in US, Russia, China, Australia, which was lucky to be near the equator during the Carboniferous Period; show Carboniferous Appalachia) cclvi. Where do we normally find oil/gas? 185. offshore in Middle East, which was lucky to be shallow and near the equator during much of the Paleozoic and Mesozoic Eras (show Mesozoic Middle East) 186. Why is oil sometimes found on land as well? (b/c plate tectonics moves crust up---this also explains why marine fossils are found on land) j. (probably skip) Purity of the fossil fuel depends on how long ago it formed, i.e., vertical position in the fossil record for coal. Older reserves have had more time and more pressure for the impurities to be pushed out of the sample. XXXV. Review class (groups discuss) k. **Oxygen**: Explain the role of oxygen during our evolutionary history using the following terms: *photosynthesis, GOE, 1^st^ Snowball Earth, ozone, reinforcing feedback, aerobic respiration, ATP, dinosaurs, fossil fuel* l. **Paleogeography**: Explain the data that led scientists to conclude the Appalachians were connected to the Scottish Highlands at the equator \~350mya m. **Fossil fuel**: Explain why there is so much coal in Appalachia using the following terms: *Carboniferous Period, equator, rainfall, land plants, photosynthesis, pressure* XXXVI. Tuesday (intro to biodiversity) n. Prep hw5 o. Bring: lecture notes, laptop, roll, graded stuff p. Prepare on computer before class starts cclvii. Powerpoint cclviii. YouTube (\~15 of them) cclix. Coursepack cclx. Googledoc for biodiversity group contest: tinyurl.com/sci1260-12 q. Before class: hand back graded stuff, e.g., Quiz1 r. Announcements cclxi. We've learned names/order of eons and eras -- it's time to learn periods as well. cclxii. Quiz 2 and Quiz 3 on p.26: Fill out p.27 (in groups for Quiz2, by yourself for Quiz3) s. Practice question to discuss in groups: Each term on the left caused one of the effects on the right. Match the pairs, explain the mechanisms, and identify in one word the common theme that unites everything. cclxiii. Loss of methaneFirst Snowball Earth (OXYGEN combines with methane to form CO2, a much less potent greenhouse gas. The atmosphere therefore traps much less heat, and global cooling leads to the first Snowball Earth) cclxiv. OzoneUV protection (OXYGEN in the atmosphere converts to O3, also called ozone, which provides protection against harmful UV rays of the sun) cclxv. Aerobic respirationlarge body size (OXYGEN in the atmosphere allows organisms that can do aerobic respiration to accumulate 18X as much ATP energy, which allows these organisms to evolve much larger body size. Increased oxygen levels explains 1) Cambrian explosion (origin of most animal groups -- generally larger in body size than the earlier protists), 2) giant amphibians during the Carboniferous and Permian Periods, and 3) giant reptiles during the Jurassic and Cretaceous Periods) cclxvi. PhotosynthesisGreat Oxygenation Event (OXYGEN is a byproduct of photosynthesis. When cyanobacteria evolved photosynthesis they forever changed the Earth, thus making it more habitable from a human perspective) cclxvii. Tropical Appalachia during Carboniferous Period coal formation (high OXYGEN levels during the Carboniferous Period meant lots of biological productivity, especially in the tropical countries, which always have the most rainfall and which, at the time, included Appalachia. All that biomass would accumulate and eventually form coal) XXXVII. Context for where we are in our Journey Through Time -- show p26 - What is left to learn? t. Names and order of periods (hence Quizzes 2&3 in our next two class periods) u. Biological events of the Phanerozoic Eon and when each event happened cclxviii. Intro to biodiversity, phylogeny of life (prerequisite to everything else) cclxix. Origin of various groups, e.g., flowering plants, trilobites, dinosaurs cclxx. Habitat transitions, e.g., waterland, landair cclxxi. Mass extinctions XXXVIII. Intro to biodiversity (group contest) v. 1-min video trailer for *Life*: w. Group contest (tinyurl.com/sci1260-12) cclxxii. Shared googledoc with 7 student groups, with each group on a different page of the googledoc: each group will claim one page of googledoc by writing their names at the top of the page (pick a scribe) cclxxiii. Each team writes on their page of the googledoc as many species as they can think of in 30s; team with the most diversity wins the prize (choosing which videos we watch) x. Analyze what they wrote cclxxiv. Point out that many species listed are similar to each other. Which species on the list could you lump together, and why? cclxxv. Keep lumping species to settle eventually on the list of 11 taxonomic groups shown on p.32 cclxxvi. See which group has maximum diversity (they get to choose the first four videos) y. Watch 1^st^ video clip z. Overview of taxonomic groups (diagram) cclxxvii. Three domains: Bacteria, Archaea, and Eukaryotes cclxxviii. Within Eukaryotes: three large multicellular taxa = animals, plants, and fungi; all other euks are called 'protists' cclxxix. Within animals: two main groups = invertebrates, vertebrates cclxxx. Within vertebrates: five groups = fish, amphibians (1^st^ tetrapods), reptiles, mammals, birds cclxxxi. How many species in each taxa? 187. As humans we are biased towards thinking about large vertebrates like ourselves, but verts form only a tiny slice of the \# of described species -- most verts are fish 188. Most described species are insects (subset of invertebrates) 189. Most of the remaining described species are either plants or other invertebrates, e.g., mollusks, worms 190. Fungi, bacteria, Archaea, and protists are all dramatically undercounted; we are mostly clueless about the species found in these taxa cclxxxii. Play "Where's Waldo?" In the large collage showing dozens of species, find at least one example from each of the 11 taxonomic groups (use powerpoint color pen) a. Overview of what to know about biodiversity for *Journey Through Time* cclxxxiii. Basic timeline for when various taxa originated? (check p. 25 and 26) cclxxxiv. How are taxa related to each other? (p. 33 -- THE tree of life) cclxxxv. Similarities and differences between taxa (table on p. 32, we will map traits onto phylogeny) cclxxxvi. Warning: Details can get daunting, so we will intersperse videos as needed to break things up. The concepts aren't that complicated -- just lots of stuff to remember b. Big theme = Life diversifies (share examples) cclxxxvii. Means we need to understand the unity and diversity of life cclxxxviii. Illustrate the basic taxonomy using color diagrams c. Video clip \#2 XXXIX. Fill out table on the unity and diversity of life (p.32) Taxonomic group Type of cell \#cells Energy Moves? Backb Body covering ----------------- --------------- ------------ -------- -------- ------- --------------- -------- ------------------------- Bacteria Prok Single Varies varies no n/a Archaea Prok Single Varies varies no n/a Protists Euk Varies Varies varies no n/a Plants Euk Multi Photo no no n/a Fungi Euk Multi decom no no n/a Animals Invertebrates Euk Multi Eats yes no varies Vertebrates Fish Euk Multi Eats yes yes scales (fish scales) Amphibians Euk Multi Eats yes yes slimy skin Mammals Euk Multi Eats yes yes hair Reptiles Euk Multi Eats yes yes scales (reptile scales) Birds Euk Multi Eats yes yes feathers d. Prok (since 3.5bya) vs. euk (since 2.1bya) -- reminder of difs cclxxxix. Both have cell membrane, watery goop (cytoplasm) and DNA ccxc. Differ with regard to... 191. Size: proks small (fist), euks big (whole body) 192. membrane-bound organelles (only in euks, e.g., mitochondria, chloroplasts) 193. organization of genome (single, short, circular c-some in proks; multiple, long, linear c-somes w/in nucleus in euks) e. Single-celled vs. multicellular ccxci. Single: includes all proks and some euks, originated in 3.5bya ccxcii. Multicellular: includes plants, fungi, animals, and some other euks, originated in 1.2bya f. Three strategies to get energy ccxciii. Photosynthesis---from the sun using leaves, e.g., plants ccxciv. Decomposers---absorb dead organisms through root-like appendages, e.g., fungi ccxcv. Eaters---ingest other organisms through the mouth, e.g., animals ccxcvi. (plus other strategies) g. Moves? h. Backbone? i. Types of body coverings for animals ccxcvii. Inverts -- varies, e.g., exoskeleton, slimy skin ccxcviii. Fish -- scales ccxcix. Amphibs -- slimy skin (breathe through skin) ccc. Reptiles -- scales (not homologous with fish, example of convergent evolution) ccci. Mammals -- hair (evolved from reptilian scales) cccii. Birds -- feathers (evolved from reptilian scales---more obvious than for hair) j. Video clip \#3 XL. Phylogeny for THE tree of life (students should memorize p. 33 and we'll do a variety of activities to help you learn it); Organisms on the tree: Bacteria, Archaea, Protists, Plants, Fungi, Invertebrates, Fish, Amphibians, Reptiles, Mammals, Birds) k. Explain the root of the tree ccciii. Bacteria often swap DNA between species, which makes it impossible to determine the phylogenetic relationships at the root of the tree of life between the early prokaryotes ccciv. We know that three domains of life emerged 194. Bacteria (all single-celled prokaryotes) 195. Archaea (also single-celled proks) u. Discovered only in the last few decades v. Consistent chemical difs from bacteria (e.g., presence/absence of peptidoglycan), but we will ignore difs; just know they differ 196. Eukaryotes (single-celled and multicellular euks) w. Includes every organism you can see with your eyes (i.e., multicellular) x. Also includes some microscopic protists (e.g., amoeba, paramecium) l. Data used to build this tree cccv. Comparing anatomical similarities and differences btwn taxa, e.g., mammals, birds, reptiles, amphibians and fish all have a vertebral column so all belong in a single vertebrate lineage (p. 32 helps to summarize similarities and differences) cccvi. Also lots of comparison of DNA sequences m. Reminder for how to determine relationships on a phylogeny n. Explore relationships on THE tree of life cccvii. Who is most closely to a fish---a bird or an invertebrate living in the ocean? cccviii. Who is most closely related to a mushroom---a human or a plant? cccix. Who is most closely related to an amoeba protist---a lizard or a bacteria? o. Using the table, help the students add ticks to THE tree of life on p.33 cccx. don't look at answers on p. 34 until you have attempted ticks on your own using p. 33 cccxi. Traits: Eukaryotes, Vertebral column, Walk on land, Feathers, Flight, Hair p. Real-life examples cccxii. 8spp: ant, cat, cyanobacteria, crocodile, diatom (type of protist), frog, human, trout (do this one as a class) cccxiii. Video clip \#4 cccxiv. 10spp: blue jay, dog, grass, lizard, moss, mushroom, robin, salmon, snail, tuberculosis (type of bacteria) (students work on this one, either individually or in groups, then class reviews answer) cccxv. Optional group assignment: bread mold (type of fungus), butterfly, chicken, pine tree, proteobacteria, salamander, tulip, yeast (type of fungus) XLI. Review Qs XLII. Video clips of some of the major taxonomic groups (links on ppt slide) q. try to notice similarities and differences r. Last video: Play the first 4min through the evolution of hominids: "History of entire world, I guess" ; end at music "That's a human person" XLIII. Thursday (fossil record of Phanerozoic) s. Prep hw5 t. Before I leave office cccxvi. Set up fossil record activity on moodle cccxvii. Check fossil record supplies in cabinet (fossils, butcher paper) u. Bring: lecture notes, laptop, roll, team quiz2 (1 copy/group needed for quiz) v. Right after I arrive in classroom: cccxviii. Set up fossil record activity (scatter fossils, and get butcher paper ready) cccxix. Set up polleverywhere, coursepack, hw5, youtube video w. Review answers to hw5 x. Announcements cccxx. Review the instructions for P-list of references (due next class) 197. emphasize numbering each ref, using a professional citation format, and writing at least a sentence next to each reference 198. Big picture: you should have been finding and learning from a variety of refs cccxxi. Individual quiz on eons/eras/periods next class (same quiz as today, but for individuals) cccxxii. Oral/video/podcast presentations start next class period (Ally S) 199. class etiquette during presentations 200. non-presenting students should listen and provide feedback, but exams will not cover any presentation content unless the content was also covered by me or in the readings y. Quiz2 -- groups; (after you finish, discuss in groups the Qs on p.35 of coursepack, which will help you to review Unit 2 so far) XLIV. Review Unit 2 so far (show p. 35) z. Scientific certainty -- It's useful to distinguish what is well-supported vs. what is plausible vs. what is incorrect a. Group discussions of scientific certainty: For each statement below, describe our **level of certainty**, describe the **data** relevant to the statement, and describe what **inferences** derive from the data cccxxiii. Which two statements are incorrect? 201. Humans have existed ever since the origin of the Earth (incorrect; the fossil record clearly shows that humans are a recent addition) 202. Prokaryotes and eukaryotes originated at approximately the same time period (incorrect; proks originated 3.5bya, euks originated 2.1bya) cccxxiv. Which four statements are very well-supported? 203. Earliest life was simple, not complex (very well

Unit 2 Lecture Notes - History of the Earth PDF

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