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Calculating Bacteria

Biology: AQA GCSE Higher, topic 1.1.30

Population of Bacteria

Bacteria multiply through simple cell division (binary fission), in which one cell divides to produce two cells. The average time for how often the bacteria divide is called the mean division time of that population.

Estimation

Estimation

  • A future population of bacteria can be estimated by multiplying the current population by two for every mean division time (time it takes for the bacteria to divide) that passes.
  • Divisions can happen as fast as every 20 minutes when the conditions are ideal.
Equation

Equation

  • To calculate the future population of bacteria, we multiply the current population by 2 to the power of (time passed ÷ mean division time).

  • As an equation, that's current population x (2 ^ time passedmean division time{\frac{time \ passed}{mean \ division \ time}}).

Test yourself on Calculating Bacteria

  • A strain of bacteria has a mean division time of 30 minutes. A group of 4 bacterial cells is left to grow. How many cells will there be at the end of 4 hours?

  • A strain of bacteria has a mean division time of 40 minutes. A group of 2 bacterial cells is left to grow. How many cells will there be at the end of 8 hours?

  • Colony A and Colony B start with the same number of bacterial cells. Colony A has a mean division time of 20 minutes and Colony B has a mean division time of 40 minutes. Which colony will have more cells after 2 hours?

  • Which of the following are true of the mean division time of a population of bacteria?

  • In the equation for future bacterial population, what is the current population multiplied by?

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