Math Connection: Growing a Billion Bacteria (lesson 2) Overview: In this activity, you will calculate and graph the exponential growth of bacteria.

Materials (per individual student) · graph paper · pencil · colored pencils

Connections You can use your understanding of bacterial growth as supporting evidence to explain why only one or a very few antibiotic-resistant bacterial cells can still result in a big problem.

Procedure Follow these steps to complete the activity:

For each time interval on the Growing a Billion Bacteria data sheet, calculate the number of bacteria that will have grown in the bacterial population.

Assume:

a. All the bacteria survive to reproduce.

b. The population of bacteria in Strain 1 doubles in number every hour.

c. The population of bacteria in Strain 2 (E. coli) doubles every 20 minutes.

Once you have completed the data table, graph your results on graph paper (or draw your own graph)

a. Label each axis.

b. Give your graph a title.

c. Use a different color for each bacteria strain.

Copy this form on a lined paper, numbering from 1-32, and fill it out

(can be done in groups, but to get credit, each person must upload their own):

Analysis and Conclusions Reflect on the following questions:

1. How many hours did it take each strain of bacteria to grow to a million cells?

2. How many hours did it take each strain of bacteria to grow to a billion cells?

3. How many hours did it take each strain of bacteria to grow to 2 billion cells?

4. How many times bigger is a billion than a million?

5. Did you see a pattern developing as you calculated?

Try writing a simple formula for calculating the number of bacteria in Strain 1.

6. Considering that during a treatment with an antibiotic, very few cells may survive because they are resistant, how would you

explain to others why the survival of such a few cells can still result in a big problem?