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Development_of_Life - Development of Life Stephen...

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Development of Life Stephen Eikenberry 02 September 2010 AST 2037 1
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Evolution This time with a capital “E” Reproduction occurs via DNA Any change in the DNA from one generation to the next creates “mutation” Causes of mutation: Radiation (all those rock decays; cosmic rays) Chemical contamination “Transcription errors” Random mutation produces wide range of changes 2
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DNA Mutation Examples 3
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Natural Selection Some mutations will be competitively “helpful”, some neutral, some disadvantageous Natural selection: those with competitive “edge” more likely to succeed in reproducing; those without are less likely 4
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Natural Selection: Examples We have seen this in action on even short timescales: Cockroaches and insecticide TB bacteria and antibiotics Light/dark pepper moths in England: Prior to 1800, mostly light-colored with occasional dark ones (collector items) After Industrial Revolution, trees darkened by soot, dark ones camouflaged, light ones easy to see Light ones disappear (eaten by birds!) Population now dominated by dark moths 5
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Back to Early Life Old fossils – like cyanobacteria Then … Stromatolites Lots and lots of stromatolites! 6
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Stromatolites Large agglomerations of single-celled organisms First they form “microbial mats” (i.e. “pond scum” layer) These layers live, die, get covered by silt Next mat forms, etc.
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