Lecture 3 Microbial Evolution

Lecture 3 Microbial Evolution - Microbial evolution...

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Click to edit Master subtitle style Microbial evolution Evolution is the emergence of new species as a consequence of natural selecton
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Charles Darwin On the Origin of Species by Means of Natural Selection Darwin Days on campus Xxx Darwin proposed that evolution proceeds by natural selection, which, by acting on naturally occurring variation within populations , favors advantageous characteristics. QuickTime™ and a  decompressor are needed to see this picture.
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Fossil records Evoultinary history of plants and animals Presence of fossil records in geological strata and data by radioisotopic decay Time-lapse photography Fungal associations with root tissues of early plants visible in fossils Spores preserved Fossils limited to the time of Camrian period, 500 million years ago What about the 3.5 billion years preceeding that period? QuickTime™ and a  decompressor are needed to see this picture.
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The Solution to microbial classification challenges: Molecular Phylogeny The classification of organisms based upon their evolutionary relationships, their descendence from a common ancestor determined by comparing the sequences of common molecules Microbes are simple, but they have complexity in protein, DNA and RNA sequences.
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The information in the sequences of macromolecules Once the central dogma was deciphered DNA-RNA-protein Sequence of monomers in an organism’s macromolecules holds information about evolutionary history Identity and position of each monomer, base or aa If changes in sequence are neutral and random, they consitute a molecular clock. The number of differnces between homologous macromolecules in two organisms should be a measure of time since they shared a common ancestor. The rate of the clock could be estimated by comparing the probable appearance of certain microbes with geological history, e.g. appearance of oxygen and associated microbes.
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phylogeny marker The gene must be present in all organisms of interest. The gene cannot be subject to transfer between species. The gene must display an appropriate level of sequence conservation for the divergences of interest. The gene must be sufficiently large to
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Lecture 3 Microbial Evolution - Microbial evolution...

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