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Proterozoic Eon lecture notes.doc

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University of Ottawa
Jon Houseman

Proterozoic Eon Slide 2Proterozoic Eonoxygen atmosphere makes appearance at the end of the Archean eon anaerobic bacteria go to places where there is no oxygen ie depths of the ocean since the world has started to become filled with oxygen aerobic bacteria make their appearanceappearance of singlecelled eukaryotesno progression beyond singlecelled eukaryote organisms during the Proterozoic eon world contains aerobic bacteria anaerobic bacteria and singlecelled eukaryote organismsperfection in singlecelled organismsno jump to multicellularitySlide 3prokaryotes are divided into archea and bacteriasinglecelled eukaryotes stem from the archea archea are closely related to eukarya and distantly related to bacteriaSlide 4 refer to table 211Cell Wallimportant for maintaining cellular integritymay have evolved once and every organism has inherited this type of cell wall analogous and convergent evolution for cell wallsdoesnt tell us about the evolution of these groups Plasma Membraneunbranched zigzag pattern for fatty acid chains in eubacteria and eukarya branched nonzigzag pattern for the plasma membrane in archea convergent evolution for fatty acidssimple chains arose firstOccams razor simple to complexeukaryotes and bacteria arose at the same time with the unique membrane system which diverged off to create the archea this theory is inverted compared to the generally accepted theoryFlagellaarchea and bacteria flagella spin with a motor eukarya motor beats independently evolved event and is not helpful Translationif there has been a modification it would have been shared by all descendents eubacteria appear to be most primitive based on this Histone Proteinsmechanism for wrapping DNA and protection in bacteria DNA folds on itself to create the structure that protects and stabilizes the DNA no proteins involvedeukarya and archea are using the same type of proteins to package and stabilize DNA within the cell the archea are very similar to the eukaryawhen we look at the evolution of these 3 groups the bacteria diverge very early on with the RNA polymerase and DNA folding and these are unifying traits for eukarya and archea when the first singlecelled organism arose it resembled bacteria and over time it specialized improved RNA polymerase DNA protection etc the phylogeny shows that bacteria are primitive compared to the archea which share advanced traits with eukarya the difference is that eukarya will put their genetic material in a membraneSlide 5 Nuclear Envelopefor a cell lifes processes occur on surfacesif there is a lot of activity in the cell you need to increase the amount of surface area in order to supply the cell invaginationinvaginating membrane allows for increased surface area and this ends up surrounding nuclear material the origins of the nucleus2 plasma membranes surrounding the nucleus nuclear envelope inside the nucleus there is biochemical optimization for DNA replication and delivery we have separated the nuclear environment from the cytoplasmic environment in the nucleus DNA and RNA is createdin the cytoplasm translation can occur compartmentalizing processes allows for efficiencynuclear pores allows for communication between the nucleus and the cytoplasm the same infolding creates the endoplasmic reticulum Slide 6Endosymbiosis of Bacterial Cellsorigins of the mitochondriapartitioning of energy systemat some point in time a large bacterial cell engulfed a bacterium that had the electron transport chain in it and when it engulfed it normal way of feeding it kept some plasma
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