Students investigate an example of new traits arising in populations by watching a video that shows the growth of bacteria on increasingly high concentrations of antibiotics as the bacterial genome accumulates mutations that confer antibiotic resistance. Students wonder how these mutations can develop so quickly. Students create a mathematical representation of bacterial reproduction to model the speed at which these populations grow to figure out that while mutation rates make it seem like mutations are very rare, they are instead quite common due to the rate at which bacterial populations reproduce. They extend this to the rock pocket mouse model and see that in a case where organisms do not reproduce as quickly, the sheer size of an organism’s genome and the number of offspring produced in a generation still guarantees mutations will accumulate over time. Finally, students return to their consensus models and use them to make predictions about what would happen in the case of specific mutations in different environments. Then they test their predictions using a computer simulation and consider the affordances of one type of model over another.

This is Lesson 5 of the High Altitude Living Unit.

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Student Materials

Per Student

• Science News: 5.1 Transcript for Watch antibiotic resistance evolve
• 5.2 Student Handout Bacterial Growth and mutation rates

HHMI BioInteractive:

• 5.4 Using our natural selection model to make predictions
• 5.5 Exit Ticket - Why do some populations have a higher frequency of alleles that are linked to high arterial oxygen saturation?
• Access to internet connected device to use for the PhET simulation
• PhET: Natural Selection

Teacher Materials

• Lesson 5 Slide Deck
• YouTube: Bacteria Growth
• Science News: Watch antibiotic resistance evolve
• HHMI BioInteractive: Natural Selection and the Rock Pocket Mouse