GEO 102 Exam 3 Study Guide Lectures 22 30 Lecture 22 October 22 Time Scale to Memorize Eons Hadean Archaen Proterozoic Phanerozoic Eras of the Phanerozoic Paleozoic Mesozoic Cenozoic Periods of the Paleozoic and Mesozoic Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic and Cretaceous Origin of the Universe 13 75 billion years give or take 0 11 o Initially inferred from expansion Doppler shif o Radiation remains cosmic background radiation o First true atoms formed 379 000 years afer Big Bang Origin of the Sun and Earth Matter from prior stars condensed gravity Planets accreted from rotating disk of matter Less volatile matter near sun stony planets less dense accreted farther gaseous planets Moon formed from early impact The Atmosphere Originated through outgassing 1st one mostly H was lost to solar wind Core differentiation magnetism protect 2nd Lecture 23 October 24 Core Differentiation Early Earth was homogenized Over time as short as 30 million years dense matter Ni and Fe sank to form core Acted as an electro magnet and protected 2nd atmosphere from solar wind o 1st atmosphere is lost Water Came from comets but Earth used to be so hot that it could not exist in liquid form First all vapor Light could not penetrate Cooled to condensation point Rain filled basins Oxygen Came much later Mostly from photosynthesis and chemosynthesis First oxygen from photochemical dissociation o Very small amount 2 of today Larger quantities came from photosynthesis o Seen in BIF s o Red beds o Initially from Prokaryotes Prokaryotes life before seeds Single cell organisms without a nucleus Tectonics Weathering Atmosphere and Climate Extensive continents by 3 6 Ga Initial uplif led to weathering Beginning of CO2 cycle o Weathering o CaSiO3 CO2 CaCO3 SiO2 o Melting of marine critters at subductions o CaCO3 SiO2 CaSiO3 CO2 CO2 Weathering Thermostat Feedback is critical Increased tectonic activity leads to new land and uplif This leads to increased weathering Increased weathering traps CO2 in resultant sedimentary rocks Rocks are subducted and cycle resumes Feedback Hot periods increase rains and water vapor heating the Earth more Rains increase weathering Ne sedimentary rocks trap CO2 Cools the Earth and lessens precipitation and weathering Sedimentary rocks subducted and it cycles Lecture 24 October 27 What is Life How do we know something is alive o How is a rock different from a tree o Reproduction o Metabolism a sequence of chemical reactions What is a Virus o Not alive o It has DNA o It reproduces o But it can t reproduce by itself It has to hijack a cell in some other body o It doesn t metabolize by itself either o Outside another body it simply exists o Viruses evolve Between life and not life Viruses are in a grey area They DO NOT represent the first proto life Microspheres might better resemble the first life o They are organic carbon based but arise by themselves o They grow and divide like cells but more randomly What are living things made of Amino acids life s building blocks o You may have heard of them from your food o Can originate from non living things How did they originally form o Miller Urey experiment o Chemosynthesis o Geobiology Did life come from rocks or clay or undersea volcanoes Many think so How do they make amino acids You need o Carbon nitrogen hydrogen and oxygen o These are in the early atmosphere CO2 H2O N2 CH4 and NH4 o An external energy source is needed to start the reaction o Lightning o Chemical energy Experiments Miller Urey showed it could be done but used the wrong atmosphere More recent work has done this in a wide variety of circumstances Several possible cradles of early life have been identified This is but the first step though Proteins Amino acids are part of proteins Our bodies synthesize proteins How did they begin o Simple proteinoids have been formed in the lab o Experiments suggest that it may not have happened in water afer all Group of protenoids cluster and form cell like structures protected by membranes Is this how it happened There is still a lot to be learned and it is developing story RNA and DNA o Reproduction o Space The geological record s earliest evidence of life is in indirect o Stable carbon isotopes at 3 8 bya The first undisputed fossils show up about 3 5 bya o Prokaryotic o Anoxic can not live without oxygen What did these organisms eat The earliest life is derived energy from breaking down components in their environment o Would not have lasted long Later life would ferment materials o Molecules such as sugars are split releasing carbon dioxide alcohol and energy About 3 5 bya photosynthesis began to be widespread Take home tip how oxygen became popular One way didn t require life Phot and chemosynthesis Life is from building blocks that can self assemble Still looking for how to tell if things are life life in extreme environments and making synthetic life Lecture 25 October 29 Introduction to free oxygen two processes introduced free oxygen into the atmosphere o Hadean Archean 1 Photochemical dissociation involves ultraviolet radiation in the upper atmosphere a The radiation disrupts water molecules and releases their oxygen and hydrogen b This could account for 2 of present day oxygen c But with 2 oxygen ozone forms creating a barrier against ultraviolet radiation 2 More important were the activities of organisms that practiced photosynthesis Life and atmosphere The first process making ozone helped to make later life o UV light destroys key building blocks of life The second process could only occur because of life o Irony is that oxygen is deadly to the organisms that produced the oxygen What were these organisms Single cell true bacteria Not many organelles simple cells Photosynthetic and chemosynthetic That produced oxygen as a metabolic product First fossils Photomicrographs from western Australia s 3 3 to 3 5 billion year old warrawoona group Stromatolites Present day stromatolites grow as sediment is trapped on sticky mats of blue green algae cyanobacteria o Now restricted to environments where snails cannot live The oldest know undisputed stromatolites are found in rocks in South Africa o 3 0 billion years old o Probable ones from the Warrowoona Group in Australia o 3 3 to 3 5 billion years old Lecture 26 November 3 Why do geologists divide time up the way we do o Mostly due to fossils Appearance and extinction o Rarely rock type o Sequence Sea level o Age dates o Geochemistry Big