UMD GEOL 104 - Paleontologists and their achievements

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Paleontologists and their achievements:- R Owens: named Dinosauria- O.C. Marsh and E.D. Cope: rivalry over fossils- J. Ostrom: Dinosaur Renaissance- Buckland and Mantel: Megalosaurus, Iguanodon & Hylaeosaurus- Steno, Hutton and Smith: Developed principles of stratigraphyMajor changes in our understanding of dinosaurs since the early 19th Century: originally thought dinosaurs were only big, going back and forth between if they were cold or warm blooded, we now know they aren’t extinct Dinosaurs: the concestor of Iguanodon and Megalosaurus and all of its descendants, “fearfully great lizards”Rocks:- Metamorphico Formed by recrystallization of previous existing rocks due to intense head and/or pressureo Rocks are “baked” and/or “squashed”, but not melted (or they would become igneous…)- Igneouso Formed by the cooling of molten materialo Cooled on the surface (volcanic) or while still underground (plutonic)- Sedimentaryo Formed by accumulation of bits of previously existing rock and/or organic matter  Bits of previous rock and/or organic matter are called sedimento Naturally creates horizontal beds called strataSedimentary rocks:- Biogenic sedimentary rocks: sediment made of solid bits of organic material o Coal: buried remains of plant lifeo Many types of limestone are made primarily of the shells of once-living thingso Made of calcium carbonateo Typically form in salty water (and thus marine or brackish lakes)- Chemical sedimentary rocks: sediment is in the form of dissolved bits (ions) that precipitate out of water- Detrital sedimentary rocks: sediment is grains of various sizes weathered from previously existing rock, cemented together by minerals in the ground and watero By far the most common in which dinosaur fossils are foundo Major types: Breccia: poorly sorted, angular and rounded = close to source Conglomerate: very well sorted and round = far from source Sandstone: formed by relatively well-sorted, well-rounded particles; deposited in many environments (deserts, beaches, river beds, nearshore marine, etc.)o Detrital sedimentary cycle: Uplift to erosion to transport to deposition to lithification (typically cementation): Uplift, pushing up once-buried rocks and exposing them to the surface elements This source rock experiences erosion: weathered away and broken up by wind, rain, water, plant roots, gravity, etc. The broken fragments (sediment) are transported by water, wind, glacial ice, etc. Sediment is deposited at some location (stream bed, banks of a river, desert, delta, lake Energy of the environment (how fast the water or wind was moving) = different sized particles of sediment Sedimentary structures: traces left in the sediment by various processes before lithification- Mud Crack: indicate that mud was wet and then dried and then buried- Ripple Marks: indicate wind- Crossbeds: ripple marks in cross-section, formed by currents (wind or water)- Trough Crossbeds: shifting winds produced lots of sand (beaches and dessart) - Raindrop marks: indicates wet surface- Coal Beds: indicates abundant plant life that was buried faster than it could decay2 major types of fossils:- Body Fossils: the physical remains of an organism preserved in rock- Trace Fossils: the record of organisms' behavior preserved in rockTaphonomy: The study of burial and fossilizationModes of Preservation:- Unaltered bone: simple burial, some weathering- Permineralized: most common mode of preservation of dinosaur body fossils- Replacement: grades from permineralization- Carbonization: organic material is "distilled" under pressure, Many material is lost, but carbon film left behind- Impressions of dinosaur skin can form if the body was pressed into the mud Different organisms have different potential for fossilization:- Hard parts vs. no hard parts- Lived in erosive environments (e.g., mountains) vs. depositional environments- Lived in accessible vs. inaccessible environments2 aspects of time to consider:- Relative Time: sequence of events without consideration of amount of time- Numerical Time: dates or durations of events in terms of seconds, years, millions of years, etc.Good Index fossil: VERY common, hard parts, geographic range, different environments, distinctive features, short time duration (a few million years at most)Dating techniques:- Radiometric dating: Radioactive materials decay at predictable rate, known as the half-life; only for igneous rocks- Magnetostratigraphy: a magnet's north pole points towards geographic North, and sometimes toward geographic SouthThe 3 eras:- The Paleozoic Era ("ancient life era") - The Mesozoic Era ("middle life era"): the Age of Dinosaurs- The Cenozoic Era ("recent life era"): the Age of Mammals. We are still in the Cenozoic Era.The oldest (furthest from us in time) is the Triassic Period - crurotarsan (crocodile ancestors) rulingThe middle one is the Jurassic Period - dinosaursThe youngest (closest to us in time) is the Cretaceous Period - dinosaursConvergent Boundaries: when plates come together Mountain Ranges are erosional; water is depositionalEXAM 2Carolus Linnaeus- System of classification codified by Carolus Linnaeus (18th Century Swedish botanist) Father of Taxonomy- Many of his principles, such as Latin names for organisms, and the use of genus and species still used todayNatural Selection- Does NOT happen to individuals, only to populations (lineages)- Analogous to "artificial selection" (domestication), but operates:o On all traits rather than a few (humans can keep alive crops, farm animals, or pets that might otherwise die in the wild; obviously, wild plants and animals don't have that help!)o Over vast amounts of geologic time, rather than just a few generations- Does NOT require simple things evolving into complex: sometimes a simplified mutationof a structure might be advantageous than the ancestral complex one (hence, vestigial organs)- Cannot evolve towards something with a goal in mind; only favors variations that are advantageous at the time of selectionDarwin & Wallace’s observations:- Variability: There is variation in all populations; no two members of a population are totally identical.- Heritability: Some (but not all) variation is inherited.- Mutations are new variations in heritable traits, caused by miscopied DNA - Superfecundity: Organisms produced far more offspring than can possibly surviveWilli Hennig: considered the founder of phylogenetic systematics, also known as

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