lecture_notes_12_03_07 - Lecture Notes December 3, 2007 Two...

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Lecture Notes December 3, 2007 Two Prokaryotic groups: Bacteria and Archaea Total biomass may be greater than that of all plant life Found everywhere: collectively, prokaryotes in and on the human body outnumber all of the cells in the body For example, one estimate is that the skin has 10 12 bacteria, that there are 10 10 in the mouth, and 10 14 in the gastrointestinal tract (It has been estimated that there are more bacteria in your digestive tract than humans on earth) Nutrition refers to how organisms obtain: Energy to power life processes Carbon to build the organic molecules of cells Prokaryotes exhibit great nutritional diversity, and include anaerobic and aerobic forms 4 modes of nutrition (source of energy, and of Carbon) Photoautotroph Chemoautotroph Photoheterotrophs Chemoheterotrophs All are present in prokaryotes; two (chemoautotroph, photoheterotroph) seem to be unique to prokaryotes Photosynthetic prokaryotes are responsible for our O 2 atmosphere The production of O 2 was a major environmental change Early in the earth’s history, there was only at best a trace of O 2 in the atmosphere Instead, atmospheric gases probably included: CO, CO 2 , N 2 , H 2 O, CH 4
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The first organisms were probably anaerobic heterotrophs and producers Cellular respiration, by which all organisms get their energy for maintenance was in the form of fermentation (producing alcohol or lactic acid) About 2.5 to 3 bya, aerobic, photosynthetic organisms, the cyanobacteria (bluegreen algae) arose (recall that photosynthesis produces O 2 as a byproduct) O 2 is corrosive and increasing levels in the oceans and atmosphere probably caused many anaerobic prokaryotes to go extinct Higher 0 2 levels allowed for the production of ozone (O 3 ), protecting the land from harmful UV radiation Higher 0 2 levels allowed for the evolution of aerobic cellular respiration--yielding
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This note was uploaded on 04/29/2008 for the course BIOCORE 301 taught by Professor Howell during the Fall '07 term at Wisconsin.

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lecture_notes_12_03_07 - Lecture Notes December 3, 2007 Two...

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