Case #2; Growth within Limits


Experiment #3a; The Effect of Carrying Capacity Investigate the effect of placing limits on population growth and the resulting growth curve.

  1. Use the "(b) Sigmoidal growth" section of the simulation.
  2. Set the initial population size to 1 bacterium, set the growth rate to 0.5, and the time to 10 intervals. These are the same numbers you used to start the previous set of growth curves.
  3. Now set a high "Carrying Capacity", 1000 and run the simulation.
  4. Write down your results and plot the growth curve exactly as before.
  5. Compare this curve with the one you obtain from the "Exponential growth" simulation. (If you don't have these curves, return to the previous simulation, set the values, and get the data again).
  6. At first glance, the two curves look almost the same; they are both "J-shaped" and appear to be exponential, unrestrained growth, but look closely at the 10 unit time interval point. In the original (exponential) simulation at the 10 unit time point the simulation gave 148 bacteria, whereas in the restrained simulation the 10 unit time interval point only gives 129 bacteria. Even here, the restrictions are being to have an effect.
  7. Reset the carrying capacity in the simulation to 500 while keeping all the other values the same. Generate another growth curve.
  8. Once again the effect is subtle, but the numbers of bacteria present at higher time values seems less.
  9. Now set the carrying capacity to 100.
  10. In 10 time points the effect is now quite marked.
  11. Reset the time interval to 20 units and re-run the simulation with the carrying capacity still at 100.
  12. Plot a growth curve with these new numbers.

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