This investigation starts with a guided procedure where students gather data on the heart rate of daphnia when the organism is exposed to 1% ethanol.  Daphnia are tiny crustaceans that are visible with the naked eye, though a microscope or stereoscope will be needed to see their heart rate.  

Daphnia are very interesting to observe because they are transparent, with the organs easily visible.  Unfortunately, they are not the easiest to care for long term, recommended you buy a culture from biological supply companies. You can also order daphnia eggs from amazon, but those have mixed reviews.

Part 2 of the investigation asks students to design and conduct an experiment that will test another variable.  Instructors can provide other chemicals to test, such as sugar, or saccharin, or students can design a test for temperature.   Part 2 is inquiry based (open-ended) and requires students to gather data, formulate conclusions and turn in a short lab report.

Grade Level: 9-12  | Time Required: 45-60 minutes

HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

NGSS – 8 Practices of Science – Planning and carrying out investigations