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Lesson summary for:
Evolution and E. coli: Natural selection in a constant environment

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Overview:
In this reading-, writing-, and discussion-based activity, 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.

Author/Source:
BiteScis

Grade level:
9-12

Time:
two to three 50-minute class periods

Teaching tips:
This lesson is meant to be used early in the evolution unit.

Concepts:
Correspondence to the Next Generation Science Standards is indicated in parentheses after each relevant concept. See our conceptual framework for details.

  • Evolution results from selection acting upon genetic variation within a population. (LS4.B)

  • Traits that confer an advantage may persist in the population and are called adaptations. (LS4.B, LS4.C)

  • Inherited characteristics affect the likelihood of an organism's survival and reproduction. (LS4.B, LS4.C)

  • Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.

  • Natural selection acts on the variation that exists in a population. (LS4.B, LS4.C)

  • Over time, the proportion of individuals with advantageous characteristics may increase (and the proportion with disadvantageous characteristics may decrease) due to their likelihood of surviving and reproducing. (LS4.B, LS4.C)

  • Scientists use experimental evidence to study evolutionary processes.

  • There is variation within a population. (LS3.B)

  • The number of offspring that survive to reproduce successfully is limited by environmental factors. (LS4.B, LS4.C)

  • Natural selection is dependent on environmental conditions.

  • Environmental changes may provide opportunities that can influence natural selection. (LS4.B, LS4.C)

  • Fitness is reproductive success - the number of viable offspring produced by an individual in comparison to other individuals in a population/species.

  • Evolution occurs through multiple mechanisms.

Teacher background:

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