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Lesson summary for:
Variations in the clam species Clamys sweetus


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This series of hands-on activities complements the HHMI DVD Evolution: Constant Change and Common Threads and has been designed to engage students in thinking about the mechanism of natural selection by encouraging them to formulate questions that can be answered through scientific investigation, data collection, and pattern recognition.

Howard Hughes Medical Institute

Grade level:

three 45-minute sessions

Teaching tips:
This activity is worthwhile, but note that it does require teacher prep that could be tedious. Also, note that executing this activity successfully depends on students exercising self control and attending quite specifically to instructions.

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)

  • 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)

Teacher background:

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