Overall goals for the measurement lessons:

Students will be able to make accurate measurements.

• Use the metric system, cm & mm
• Decide on appropriate untis of measurement
• Recognize sources of error in measurement
  
• Identify and agree on methods for measuring the caterpillar
  • Students need to discuss and agree on how to measure the larvae. This was done using line drawings to decide on which structures to include, and by settling on methods for measuring curved or moving larvae. Two students measured the same larva, and then tried to reconcile the differences in the values they obtained. Sometimes they said these differences were due to using rulers that weren't the same (attributing the difference to the tool, not the methods used). In these cases, they often used an intermediate value as the "real" value, because they could not decide which one of them was "correct." Sometimes they dismissed others' values, sometimes they averaged the two values to include everyone's data.
    
• Measure wing area or expansion (in wing expansion activity)
  • We only handled adult butterflies to tag and release them. However, students studied butterfly wing expansion using a set of images taken at intervals in the 15 minutes following butterfly emergence from the chrysalis. When students measured wing area on images of the adult butterfly, they often measured length and width of the wing as non-perpendicular lines, and were not consistent on these measures (across or within groups). This meant that their calculations for wing area (length x width) were based on inconsistent methods and differed substantially even when groups were working with the same image.