Grade Level

High School




Mary Brunson, Claire Meaders

Lesson Summary

This lesson is meant to be used early in the evolution unit. Students explore bacterial evolution occurring in a stable environment, which counters the intuitive misconception that environmental change is a necessary component to natural selection. A landmark study provides the backdrop against which students can challenge their thinking about what it means for a population to evolve. Upon completion of this lesson, students will be able to:

  • predict the fate of different mutations depending on the type of mutation and the context in which the mutation arises;
  • explain that mutations and natural selection happen, even in a constant, stable environment; and
  • differentiate between types of mutations and be able to explain why the appearance of a mutation does not always guarantee its longevity.



Science and Engineering Practices:

SP4, SP6

MA Science and Technology/Engineering (2016):

HS-LS4-2, HS-LS4-5

NGSS (2013):

HS-LS4-2, HS-LS4-4

Common Core Math/Language Arts Standards:



adaptation, allele, allele frequency, evolution, fitness, fixation, mutation, natural selection

Educator SoundBites

"Teaching today is not just focusing on 'teaching.' There are many other expectations placed on educators that take time away from preparing for classroom instruction. This activity took some of the burden off of my shoulders and allowed me to act as an educator in the classroom, guiding my students toward deeper understanding of an otherwise difficult and culturally misrepresented phenomenon."
Angela Kowaleski, Shawano Community High School, Shawano, WI

The material provided just enough challenge to be memorable and is a lesson that I have been able to refer back to when discussing other topics in natural selection, fitness, and allele frequency.
Bonnie Nieves, High School Teacher, Massachusetts

Lesson Documents


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