Infectious Disease: Evolving Challenges to Human Health
RAPID EVOLUTION

Exponential Growth

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Exponential Growth

Under ideal conditions, a population of bacteria doubles with every generation. Generation times can be less than 30 minutes for E. coli, which is found in the human gut, to 20 hours for the bacteria that cause tuberculosis. Even under normal conditions many infectious bacteria, viruses, and parasites can produce populations of billions or trillions within 24 hours.

If a bacterium divides every half hour, how many bacteria are there...

  • At two hours (4 generations)?
  • At four hours (8 generations)?
  • At eight hours (16 generations)?
  • What if they continued reproducing for 24 hours (48 generations)?
Photo of Rapid Evolution Exhibit at the Koshland Museum

Rapid Evolution

Visit the Koshland Science Museum to see the impact of rapid evolution.

The Answers

  • 2 hrs = 16 bacteria
  • 4 hrs = 256 bacteria
  • 8 hrs = 65,536 bacteria
  • 24 hrs = 281, 474, 976,710, 656 bacteria

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