Earth Sci exam review final.pdf

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Western University
Earth Sciences
Earth Sciences 1083F/G
Cam Tsujita

EARTH SCIENCE 1083 EXAM REVIEW LECTURE 18Fossilization and Information Loss fossilization is rare for dead remains to survive into fossil requires exceptional conditions scavenging after and organism dies its tissues are destroyed due to various factorsmacroscopic level large scavengers take their soft tissue small scavengers take their share microbial decay microbes break down organic matter further at molecular level often decay from inside out in animalsgut bac can jump start processPhysical and Chemical Weathering physical weathering mechanically breaks down hard mineralized tissues eg shells bone teeth mineralized tissues also tend to dissolvevia chemical weathering and erode if exposed at the surface physical physical interaction chemical chemical interactionsHard parts are preserved more often since they are more robust more stable chemically and are more resist to destruction almost never preserved intact soft tissue decay removes connective tissue keeping hardparts together gentle physical disturbance can lead toDisarticulation dissociation of hard partsFragmentation Breakage and dissociation of fragments thus formed Dissolution breakdown of hardparts via dissolutions of minerals in hardparts Abrasion Erosion of hard tissues due to sandblasting effects of suspended sediments particles note these processes affect each other ie decay of organic matter can weaken hardparts making them more prone to fragmentation and abrasion factors that promote the preservation of remainsiabsence of oxygenslows down decomposition discourages scavengingii rapid entombment discourages scavenging prevents scattering of piecesiii precipitation of stable minerals inon remains after burial Common mineral Compositions of Hard PartsCalcium Carbonate aragoniteunstable calcitestableSilicastableCalcium Phosphate stable MODES OF FOSSILIZATION GET FROM THE TUTORIALSpetrificationpermineralization filling with pores of additional minerals replacement silicification ie fossil sponge brachiopod pyritization ie pyritized brachiopod phosphatization ie shark vertebrae Molds and Casts Internal mold ie gastropod Cast ie tree trunkexternal mold ie bivalvessoft tissue preservation mineral plating soft tissue impressions Carbonization ie fern leaves and coal Refrigeration ie mammoth tar impregnation ie pickeld beetle phosphatization ie embryo of arthropod in egg amber entombment ie insects POST BURIAL PROCESSES recrystallization over time crystals of a given mineral tend to increase in size to achieve greater stability increase size of crystalsloss of detailcompaction compacted fossil shape becomes distorted trace fossil fossil of a trace of an animal walking ploughing resting footprints can show behaviour patterns stromatolites trace fossil formation by sediment accretion sediment trapping my bacterial slime mats coprolites fossil excrement he gave us a piece of dino poop LECTURE 19 Origin of Life three domains archae eukarya bacteria kingdoms eubacteria archae bacteria protista plantae fungi animalia Evolution of the Earths Atmosphere initially like jupiter rich in helium derived from solar nebula burned off by solar windescaped gravitational fieldssecond atmosphere like venus dominated by carbon dioxide from Earths interior the big burpthird and present atmosphere rich in oxygen modified from second atmosphere due to rise of anaerobic photosynthesizing organisms
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