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23 Cards in this Set
- Front
- Back
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4.5 Billion Years Ago
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how old is the earth?
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Fossils & Light Stable Isotopes
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how do we know when life started?
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Stromatolites
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structures formed by filamentous microbes and deposits formed by phototrophic bacteria; Initially anoxygenic then oxygenic
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How Life Began
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Conditions on Earth: High temperature, reduced inorganic chemicals (e.g., H2, CH4, S=, S0, NH4+,Fe2+), and high intensity radiation; chemical formation of simple organic molecules
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Primitive Life
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-only anoxic mechanisms of energy
-Early lineages of hyperthermophilic Bacteria and Archaea perform such metabolism |
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Consequences of Oxygenation of Earth
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-evolution of aerobic organisms
-more efficient energy -formation of ozone layer; life could come out from hiding -evolution of eukaryotic cell |
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Phylogeny
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-the evolutionary history of organisms
-all organisms related by decent -most commonly used gene is the 16s rRNA gene |
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Evolutionary Analysis
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The change in nucleotide sequence between the same gene in two organisms reflects the evolutionary distance between them
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Evolutionary Analysis
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3 step process:
1. Obtain SSU RNA - Role of PCR 2. Sequence the PCR product 3. Similarity by comparison to sequences in databases |
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Taxonomy
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the classification of microorganisms
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Phenotypic
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organism’s properties; Characterization (morphology, nutrition, habitat)
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Genotypic
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comparative genomics
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Phylogenetic
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evolutionary perspective
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Elements of Taxonomy
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-identification (phenotypic and genotypic)
-nomenclature |
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Phenotypic Characteristics Used in Taxonomy (Phenotypic Analysis)
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-morphology
-motility -metabolism -physiology -chemistry -other |
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Genotypic Analysis
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-DNA-DNA hybridization
-DNA profiling -MLSR (multilocus sequencing type) -GC ratio |
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Evidence of O2
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banded iron formation in sedimentary rocks; alternating iron silicates and iron oxide deposits
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DNA DNA Hybridization
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-provides a fine differentiation between microbes that are very similar to each other
-the more similar the organisms, the more similar their genomes -when DNA is denatured and allowed to anneal, the more similar the primary sequence the faster it will anneal |
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The Biological Species Concept
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a species is defined by reproduction boundaries
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What is a Microbial Species?
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> 70% DNA-DNA hybridization and > 97%16S rRNA gene
sequence identity |
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Classification
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organization of organisms into progressively more inclusive groups
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Nomenclature
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A set of formal rules which govern the naming of organisms; a binomial system:
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Type Strain
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the newly characterized species must be deposited in culture collections
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