Lecture XIII: Rocks, Fossils, and Fossilization 2/20/15Lecture XIV: The Burgess Shale and the Nature of History 2/23/15Lecture XV: Paleoecology 2/25/15Lecture XVI: Evolutionary Fauna 2/27/15Lecture XVIII: Oceanic Circulation 3/4/15Lecture XIX: Paleozoic Fauna 3/6/15Lecture XX: Phylogeny: Inferring the Pattern of Evolution 3/9/15Lecture XXI: Phylogeny cont. 3/11/15Lecture XXI: Phylogeny cont. 3/11/15Ees 1040 1st EditionExam # 2 Study GuideI. Schrag and HoffmanA. “Cap Carbonates”1. “Ice house” to GreenhouseB. C isotopes1. If no life and CaCO2 from seawater would have original ratio of 12C/13C2. If abundant life, burying organic C (preferentially 12C)a. LESS 12C available for CaCO3, so 13C is elevated3. ONSET OF GLACIATIONa. Major depletion of 13C all way down to near original source levelsII. PrecambrianA. 542MA start of common fossil record1. first evidence of complex animal life2. GlaciationsB. 1.0BADominated by prokaryotes start i. to diversify (eurkaryotes)C. 1.6BA1. Paleoproterozoic2. 1.8a. Start of buildup of atmospheric oxygenD. 2.5BA1. Archaean Eon2. 3.2 first Stramatolites3. 3.5 first fossils4. 3.8 First evidence of lifeE. 3.96BA1. Hadean Eonno preserved recordIII. First life looks lifeA. ~580Ma1. Complex animals suddenly appear (only last 20-30 million years of “Precambrian”)2. “Ediacara Fauna” Ediacara hills of South Australia3. Soft-bodied animals preserved as imprints in sediment4. Weirda. Debate overi. Belong to extent Phyla- Vs.ii. Basically a separate KingdomIV. Precambrian-Cambrian A. Cambrian1. Large Cambrian Cambrian Explosioni. Radiation2. Middle Cambrian Cambrian Explosioni. Radiation of complex large animals- “all” known phyla developedb. Sudden appearance of armored fossils3. Lower Cambriana. Sudden appearance of armored fossilsb. Trilobite tracks (but no trilobites (so no hard parts developed yet on the trilobites))c. Small, simple skeletal fossil “SSF” (small shelly fossils)B. 542MA latest Precambrian1. First hard parts2. First animal tracksC. ~570MA1. Ediacaran FaunaV. When did complex animal life start?A. “the molecular clock”1. We can measure the genetic difference or “distance” between different animals2. By estimating the rate of genetic change over time, we can calculate how long ago two different animals split from a common ancestorLecture XIII: Rocks, Fossils, and Fossilization 2/20/15I. Fossils and the Fossil RecordA. Fossil1. Tangible remains or signs of ancient organismsB. How Does a Fossil get preserved?1. Igneous rocka. Formed through cooling of molten material (magma)2. Sedimentary rocka. Formed from material deposited on Earth’s surface3. Metamorphic rocka. Formed through alteration of rock by heat or pressureII. To FormA. Need to live in an environment likely to be captured in the sedimentary rock recordB. Need to have readily preservable hard parts – mineralized parts that don’t easily rot away1. Usually, all that’s reserved are the hard parts2. Animals that lack hard parts (e.g., worms, jellyfish) are extremely rare as fossilsIII. What are the Major Biases of the Fossil Record?A. By Environment1. We really only have a record of certain kinds of environmentsB. By Time1. Eustasy:a. The rise and fall of global sea-levelb. The rise and fall of global sea-leveli. Times of high sea level: rocks preservedii. Time of low sea level: rocks eroded away2. There are chunks of time we know about, and chunks of time we really don’t know aboutC. By Kind of Animal1. In modern oceans, depending on the environment, the number of animals with hardparts can be <<50% of the total numbers of animals2. Odds are really stacked againsta. Scavengersb. Mechanical transportc. Metamorphismd. Erosione. Not exposed3. The fossil record is more like a series of snapshots than a movieIV. What are Animal Hard Parts made of?A. Calcium Phosphate (mineral called apatite)a. Our own bones and vertebratesb. Shells of many marine animalsB. Calcium Carbonate (Calcite and Aragonite)1. The material that makes limestone a. Mollusks (snails, clams, octopuses, and relatives)C. Silica1. Some spongesV. What are the Main Types of Preservation?A. Unaltered Hard parts1. Fossil is preserved exactly as it was, with internal structures and fabrics still visibleB. Recrystallization1. Original fossil composition is altered, but remains formed of same substance2. Surface detail usually preserved, but internal structure are removedC. Replacement1. Original fossil material is totally replaced by a different substanceD. Premineralization1. Open pore spaces fill with outside minerals, often greatly improving preservation potentialE. Molds1. Original fossil dissolves totally away, but the space in the rock remainsa. Can often make a cast and get replica of original fossilF. Impressions1. “Squashed molds”2. Soft/semi-hard organisms (insects, plants) get squished flat and leaves impression behindG. Trace Fossil1. Not the animal themselves, but the marks in sediment they left behinda. Burrows, tracks and trails, resting impressionsLecture XIV: The Burgess Shale and the Nature of History2/23/15I. LagerstaettenA. Extraordinary preservationB. The Burgess Shale1. Middle Cambrian, Yoho National Park, British Columbia, Western Canada2. Charles Walcott 1910-19213. Harry Whittington 19664. Des Collins 1980s C. Limestone deposit1. Cathedral Formation2. Stephen FormationD. Biota1. No bioturbation of scavenging2. 98% soft-bodied 3. Most animals were alive at start4. Most were killed really quicklya. Died before defenses could be raised or before they knew what was happening5. Preserved iron aluminum silicates and pyriteE. Species of fauna Species usually preservedMarginal reefLandBS FaunaFailure of platform edge“adbration: deposit“Stagnation fossil-lagerstaette”1. 13 species of Sponges 0 species (no information)2. 6 species of Brachiopods 6 species3. 1 monoplacopharan mollusk 14. 1 hyolithid 05. 5 priapalids 06. 5 polychaetis 07. 2 onychopharans 08. 2 cnidarians 09. 1 chordate 010. 3 echinoderms 211. 29 arthropod 1112. By numbers, only 2% normally preservable F. Controversy1. Stephan Jay Goulda. “Cone of Increasing Diversity”b. OR “Diversification and Decimation”2. Anomalocarisa. 1978 Conway Morris prepares Laggania, exposes a Peytoia fossilb. 1982 Conway Morris publishes paper of Peytoia, considers it “peculiar: medusoidc. Whittington finds Anomalocaris attached or on top of Lagganiad. Also finds Peytoia on top of Anomalocaris with e. Peytoia =