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Lesson summary for:
A Step in Speciation


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Students compare different subspecies of a California salamander on a grid map of California to focus on patterns of their distribution, their likely evolutionary relationships, and probable sequence of formation from the ancestral salamander.


Grade level:

Two 50-minute periods

Teaching tips:
Much of the "busy" work can be streamlined to make this an effective activity at the undergraduate student level.

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

  • Evolution is often defined as a change in allele frequencies within a population.

  • Natural selection and genetic drift act on the variation that exists in a population.

  • Speciation is the splitting of one ancestral lineage into two or more descendent lineages.

  • Speciation is often the result of geographic isolation.

  • Occupying new environments can provide new selection pressures and new opportunities, leading to speciation.

  • A hallmark of science is exposing ideas to testing.

  • Scientists can test ideas about events and processes long past, very distant, and not directly observable.

Teacher background:

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