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

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