02.Growth Curve

Ok on monday ok on tuesday ok on wednesday ok on

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OK on Monday, OK on Tuesday, OK on Wednesday, OK on Thursday, but suddenly Sour on Friday. This is also why the Onset of the Symptoms of Food Poisoning is usually so Sudden. If you plot Exponential Growth over Time on Arithmetic Graph Paper, you’ll get a highly characteristic J-Shaped Curve (Figure 2-1a). Such a Curve may be esthetically pleasing but it’s not very Useful for our Purposes. If instead of plotting the Numbers (16, 32, 64 ...) you plot the Log of these Numbers (1.204, 1.505, 1.806 ...) over Time on Arithmetic Graph Paper, the Result will be a highly characteristic -- and eminently Useful -- Straight Line (Figure 2-1b), which Microbiologists sometimes confusingly call a “Straight Curve”.

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Lab 2 Page 17 By the End of Today’s Lab you’ll have 5, or possibly 6 Numbers. As mentioned previously there are two Ways you could plot these Data. One Method would be to plot the Actual Numbers on Arithmetic Graph Paper. Another Method would be to determine the Log of each of these Numbers. This Second Method would ultimately be far more Useful. You could plot these Logs on Arithmetic Graph Paper. It wouldn’t be too difficult. You would plot the Logs of your Numbers using the Vertical Axis Scale on the Graph Paper and the Timepoints using the Horizontal Axis Scale on the Graph Paper. Note that each Page in your Lab Notebook is Arithmetic Graph Paper. Your Niece’s Hello Kitty™ Calculator has a Log Function, but you probably still wouldn’t want to figure out the Log of each Number to make this Graph. So there’s a Third Method. We have some nifty Graph Paper that automatically plots your Arithmetic Numbers as Log Equivalents. Our Graph Paper plots the Numbers on the Vertical Axis for the E. coli as the Log for each Number, but keeps the Numbers on the Horizontal Axis for Time Arithmetic. This Special Graph Paper is called Semi-Log Graph Paper. Figure 2-1 . Panel (a) shows Bacterial Growth as plotted on Linear Graph Paper. Panel (b) shows Bacterial Growth as plotted on Semi-Log Graph Paper. _________________________ “I am wondering, why are you here?” I'm looking for someone.’ Looking? Found someone, you have, I would say, hmmm?” Right...’ Help you I can. Yes, mmmm.” I don't think so. I'm looking for a great warrior.’ Ohhh. Great warrior. Wars not make one great.” © 1980 LucasFilm Ltd. 12 10 8 6 4 2 0 0 10 20 30 40 50 60 cell density time 12 10 8 6 4 2 0 .1 1 10 100 time cell density a) b)
Lab 2 Page 18 What the Heck is Semi-Log Graph Paper? Semi-Log Graph Paper is a Type of Graph Paper designed for plotting Data from Exponential Growth (or Exponential Decay) Experiments. Any given Distance on the Vertical Axis will always represent the same Multiplication Factor. On our Semi-Log Graph Paper there is an Inch and a Half between “1” and “2”. There’s also an Inch and a Half between “2” and “4”, “3” and “6”, “4” and “8”, and “5” and “10”. An Inch and a Half represents a Multiplication Factor of 2 anywhere on the Vertical Axis. An Inch and a Half up from any Number is twice that Number; an Inch and a Half down from any Number is half of that Number.

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