Lecture 4- origins of life

Lecture 4- origins of life - Lecture 4: Origins of Life...

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Lecture 4: Origins of Life 2/15/08 Tree of life: o Life may have evolved multiple times, but all of the life on the planet may have a single origin o Certain hypotheses can be disproved, but we will never know for certain how life came about The genetic code: universal in almost every organism on earth o Gives us hints about the base of the tree of life in a single origin Spontaneous generation: o Life from non-living material taught that it doesn’t occur o People used to think dead meat turned into maggots…they did an experiment where the covered the container of meat and so maggots couldn’t enter…no maggots on meat…proved that they didn’t form from dead meat o BUT when earth first formed there were no living organisms on the planet at all, which means spontaneous generation must occasionally take place…where nonliving things must somehow be able to turn into living things…if this was not true, we wouldn’t exist o Definitely doesn’t happen commonly (such as exp with maggots) The Miller-Urey experiment: o Idea about how spontaneous generation can happen… o Took simple inorganic chemicals (NH3, CH4) that they thought were present in the prebiotic earth before living organisms…subjected them in conditions that they thought might have been present at that time (with electricity, warmer temperatures, etc)…he took samples of the solution and he found that some of the simple inorganic chemicals could form organic molecules. o He didn’t actually make living things, but he showed that under the right conditions, inorganic chemicals can go through chemical reactions and form simple organic molecules o Did another experiment: took same inorganic chemicals and instead of warming up/electrocuting…he freezes them at -78 degrees celcius. He left them frozen for different amounts of time (up to 25 yrs). Afterwards, he takes container out of freezer and analyzes what was in it…in these inhospitable conditions: organic compounds such as adenine, guanine and
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Lecture 4- origins of life - Lecture 4: Origins of Life...

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