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Oceanography Chapter 1 Scientific Method • Quiz Friday on science • Link on scientific method • http://teacher.nsrl.rochester.edu/phy_labs/Ap pendixE/AppendixE.html • Link on Nature of Science • http://www.project2061.org/publications/sfaa /online/chap1.htm?txtRef=&txtURIOld=/tools /sfaaol/chap1.htm Scientific Method • Quiz Thursday • Link on scientific method • Link to Big Bang Video Nebular Hypothesis • Earth and the rest of the solar system formed from a cloud of space dust called a nebula. • Most of the matter condensed to form the sun, small eddies condensed to form protoplanets Animation Nebular Hypothesis Link http://atropos.as.arizona.edu/aiz/teachi ng/nats102/mario/solar_system.html Sun • Eventually material concentrated so much that a process called fusion was triggered. • Fusion: Hydrogen atoms combine to release tremendous amounts of energy Formation of Earth • Link to formation of Earth http://atropos.as.arizona.edu/aiz/teaching/nats102 /mario/solar_system.html • Link to video • Link to video • Link to video Sources of Heat on Earth 1. from the remnants of heat from impacts (meteors, asteroids, comets) 2. a remnant of an early Earth event known as the Iron Catastrophe – migration of materials cause friction. 3. from compression due to gravity. 4. from the decay of radioactive elements Density Stratification •As Earth condensed its internal heat became so intense that it became molten. •Denser elements migrated towards the core, lighter towards the surface causing density stratificationmaking layers of the Earth’s internal structure according the density. Density = Mass/Volume •These layers can be characterized by either their chemical or physical composition. •Interior of Earth Lab. Chemical Composition • Chemically the Earth can be divided into 3 layers. 1.Crust – a thin 20 mi. layer composed of lowdensity rocks made of silica minerals-two types: oceanic and continental crust 2.Mantle -1800 mi. thick made of high density iron and magnesium silicate rock 3.Core- 1800 mi. made of higher density metal ( Ni and Fe) Crust Mantle Most volume cMc Core Physical Properties-5 layers 1. Lithosphere – cool, brittle outermost layer 62 mi. Plates of the lithosphere move on the Earth. 2. Asthenosphere- 62-430 mi forming the upper mantle. It is hot enough to melt portions of rock making them plastic (flowing with gradual force) – with high viscosity (resistant to flow). 3. Mesosphere- to 1800 mi., making the middle to lower mantle. It is rigid. 4. Outer core- liquid and capable of flowing 5. Inner core- rigid and does not flow LAMOI Lithosphere Asthenosphere Mesosphere Outer Core Inner Core Structure of Earth Link http://atropos.as.arizona.edu/aiz/teaching/nats10 2/mario/solar_system.html Lithosphere includes the crust plus the upper mantle and acts as a single unit Oceanic Crust under the oceans is composed of high density basalt is about 5 mi thick Continental Crust is composed of low density, lighter colored granite. Ave 22 mi thick. What would happen if this guy stepped off the boat? Mr. Wizard Video A glacier or mountain would be analogous to the containers, the lithosphere or crust would be analogous to the ship, the mantle or aesthenosphere would be analogous to the water First Atmosphere Composition - Probably H2, He • These gases are relatively rare on Earth compared to other places in the universe and were probably lost to space early in Earth's history because – Earth's gravity is not strong enough to hold lighter gases – Earth still did not have a differentiated core (solid inner/liquid outer core) which creates Earth's magnetic field (magnetosphere = Van Allen Belt) which deflects solar winds. • Once the core differentiated the heavier gases could be retained Second Atmosphere • Produced by volcanic out gassing. Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 (ammonia) and CH4 (methane) • No free O2 at this time (not found in volcanic gases). • Ocean Formation - As the Earth cooled, H2O produced by out gassing could exist as liquid in the Early Archean, allowing oceans to form. – Evidence - pillow basalts, deep marine sediments in greenstone belts. – Link to Goldilocks principle activity Oparin and Haldane • Proposed that from the simple inorganic molecules on Earth’s early atmosphere life could form. • The first step would be to form organic molecules to build the first cell. Figure Miller-Urey Experiment Miller and Urey tests out17-8 Oparin and Haldane’s hypothesis Section 17-2 Mixture of gases simulating atmospheres of early Earth Spark simulating lightning storms Condensation chamber Water vapor Cold water cools chamber, causing droplets to form Liquid containing amino acids and other organic compounds Methane Miller and Urey simulated Earth’s early atmosphere electricity simulated lightning Why did they use uV light? Ammonia Hydrogen Experiments have produce all 20 amino acids, sugars, lipids, purines, pyrimidines What is the importance of amino acids? What is the importance of nucleic acids? Polymerization led to proteins and nucleic acids such as RNA Lightning and uV light provided energy for polymerization Chemical Evolution Abiogenesis Proposed by Oparin and Haldane The abiotic synthesis of monomers Polymerization of monomers Aggregation of molecules into protobionts Origin of heredity 6. Natural section could refine protobionts containing hereditary information Once primitive RNA genes and their polypeptide products were packaged within a membrane, the protobionts could have evolved as units. Molecular cooperation could be refined because favorable components were concentrated together, rather than spread throughout the surroundings. Fig. 26.13 Liposomes behave dynamically, growing by engulfing smaller liposomes or “giving birth” to smaller liposomes. Fig. 26.12a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Protobiont Examples Coacervate (Oparin) made of polypeptides nucleic acids and polysaccharides Proteinoid Micorspheres (Fox) Liposomes (from previous slide) All protobionts: Selectively Permeable membrane Have simple means of storing and releasing energy Split like they’re reproducing Why Pre-cells with a membrane have an evolutionary advantage • Membranes help to separate the internal and external environments • There can be some control over what gets in and out • They help to concentrate substances in an area • Can form spontaneously when polypeptides and phospholipids are heated together Selective advantage for those that could metabolize • As cells or pre-cells multiplied there would eventually be a shortage of material • Those that could metabolize their own molecules had an advantage. RNA probably the first genetic molecule RNA could not only replicate itself, but it could also act as a catalyst eg. Making proteins RNA with the best autocatalytic activity would predominate Characteristic of First Cell • All had DNA • All use the same genetic code. • Most similar organisms to first cell is eubacteria. • First cells were heterotrophic First photosynthesis probably used hydrogen sulphide and hydrogen gas for electrons instead of water 3.6 bya Cyanobacteria= Blue Green Algae 3 bya produced oxygen for respiration and ozone layer How we got an Oxidizing Atmosphere • Today, the atmosphere is ~21% free oxygen. How did oxygen reach these levels in the atmosphere? Revisit the oxygen cycle: Oxygen Production – Photochemical dissociation - breakup of water molecules by ultraviolet light • Produced O2 levels approx. 1-2% current levels • At these levels O3 (Ozone) can form to shield Earth surface from UV – Photosynthesis - CO2 + H2O + sunlight = organic compounds + O2 - produced by cyanobacteria, and eventually higher plants - supplied the rest of O2 to atmosphere. Thus plant populations produced O2. • Oxygen Consumers (reduces oxygen) – Chemical Weathering - through oxidation of surface materials – Animal Respiration (much later) – Burning of Fossil Fuels (much, much later) Concept Map Section 17-2 Evolution of Life Early Earth was hot; atmosphere contained poisonous gases. Earth cooled and oceans condensed. Simple organic molecules may have formed in the oceans.. Small sequences of RNA may have formed and replicated. First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. Later prokaryotes were photosynthetic and produced oxygen. An oxygenated atmosphere capped by the ozone layer protected Earth. First eukaryotes may have been communities of prokaryotes. Multicellular eukaryotes evolved. Sexual reproduction increased genetic variability, hastening evolution. How Old is the Earth? • The generally accepted age for the Earth and the rest of the solar system is about 4.55 billion years (plus or minus about 1%). This value is derived from several different lines of evidence. • Unfortunately, the age cannot be computed directly from material that is solely from the Earth. There is evidence that energy from the Earth's accumulation caused the surface to be molten. Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface. • The oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by several radiometric dating methods). Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare, however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia. Radiometric dating measures the decay of radioactive isotopes in terms of half-life Half-life is the amount of time it takes for ½ the amount of a radioactive isotope to decay The half-life of Carbon 14 is 5,600 years If you had 1 gram of carbon 14, how much would be left after 6 half lives? 0.015 g How many years would that take? 33,600 yrs Why would be measuring a million year old fossil using C14 not be possible? How do you date a million year old fossil? Meteor video