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Lecture 10

Lecture 10 Evolution of Eukaryotes.docx

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Biology 1002B
Tom Haffie

Lecture 10: Evolution of Eukaryotes Friday, February 15, 2013 5:41 PM  Archaea don't show very much morphological complexity, not as much as eucarya  Bacteria can perform interesting biochemical functions, but this doesn't reflect intense complexity  The paradox  All morphologically complex life is eukaryotic  All eukaryotes share common complex traits  Nucleus, trafficking, cytoskeleton, sex, phagocytosis, organelles  Prokaryotes show no tendency at all to develop these types of morphological/cellular complexity  Why don't they if evolution is stepwise and gradual  What happened early on in the bifurcation in the tree of life that lead to only one domain being where all the complexity happens?  What drove the evolution of eukaryotes?  Oxygen is the key, the ability to use oxygen was the drive  Earliest bacteria were anaerobic  Uses glycolysis and fermentation to make ATP (this does not make very much ATP, so they didn't have enough ATP for major functions…)  2.2 bya cyanobacteria developed and they were able to use oxygenic photosynthesis to split water into oxygen and protons  Produced oxygen and evolved oxygen and released it into the atmosphere  This eventually increased the concentration of oxygen in the atmosphere  Bacteria that undergoes aerobic respiration  Oxphos  Lots more ATP was produced and this allowed for more functions on the part of the cell  Oxphos in bacteria  Archaea and bacteria are 1000s of times smaller than eukarya  The ETC and oxphos occur on the plasma mm'n (only on the plasma mm'n)  As the bacteria grows bigger, the surface area to cell volume ratio becomes greater  Not enough ATP can be produced per surface pn for the volume of the cell  This limits the size of the bacterium and thereby limits the number and complexity of functions that the bacterium can perform  Eukaryotic cells - more energy  Eukaryotes are much bigger so they have a low plasma mm'n surface area/volume ratio  But the plasma mm'n is not the site of oxphos for eukarya, they have mitochondria each with many oxphos centers  The internal mm'n structure is much larger than in bacteria  Lots of energy is produced  This allows the cell to support a larger genome and thereby lots of other functions that are dictated by the genome  DNA replication = 2% cell energy, protein synthesis = 75% cell energy (prokarya don't have enough ATP to synthesize novel pns  Bacteria = 13000 ribosomes, Eukarya = 13000 x 10000 ribosomes  Greater diversity of genome size as well  Endosymbiosis  Ancestral bacterium  Develops the endomembrane system derived from the infolding of the plasma mm'n
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