This lesson begins with a brief video setting the stage for the topic and open-ended discussion questions designed to elicit student ideas. Working in pairs, students then model what happens to the gut microbiome when exposed to multiple rounds of antibiotic treatment. They answer a series of questions that guides them toward the understanding that the rise of antibiotic resistant bacteria within the population is an example of evolution by natural selection. Students extend their understanding by predicting and then modeling a variation of the original scenario.

Learning Objectives

At the completion of this activity, the students will be able to do the following:

  1. Describe how antibiotic resistance in bacterial populations demonstrates natural selection.
  2. Explain why standing trait variation, heritability, and a link to reproductive success are necessary for evolution by natural selection within a population.
  3. Distinguish between evolution and natural selection.

Science Standards

This lesson addresses Next Generation Science Standards (NGSS; 2013):
  • HS-LS4-3 Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.
  • HS-LS4-4 Construct an explanation based on evidence for how natural selection leads to adaptation of populations.