How Salt Water Serial Dilutions Impact Daphnia

There are many math connections in this activity for middle school students! Besides learning how to make serial dilutions, students will see how small changes in the concentration of salt i... See More

There are many math connections in this activity for middle school students! Besides learning how to make serial dilutions, students will see how small changes in the concentration of salt in water can negatively impact a living organism. Some mathematically savvy students will be able to determine molarities, while other students will be able to create ratios and calculate percent concentrations. Everyone will have practice measuring volume and mass. Students will see firsthand how even minute amounts of salt can have devastating effects on living things. Water fleas (Daphnia spp.) are excellent specimens to use for this activity because they are sensitive to slight changes in salinity. Their demise leaves a lasting impact on the students and helps them to internalize how toxic substances can kill - even in very tiny concentrations. Since some of the Daphnia die, the teacher will need to determine ahead of time whether this will have too great an impact on students in the class. There are two data tables for teachers. One shows representative results using the various serial dilutions of salt water. The other is a worksheet that students can use as they conduct the inquiry. Students have the opportunity to become real scientists to show the detrimental effects of pollution on living things.

Using Daphnia to Teach Math

This is an excellent example of how Common Core Mathematics Standards can be embedded into an inquiry activity. The practice of creating serial dilutions, calculating percentages, and graphi... See More

This is an excellent example of how Common Core Mathematics Standards can be embedded into an inquiry activity. The practice of creating serial dilutions, calculating percentages, and graphing are skills that students will need in future science classes. Although this inquiry activity is a verification activity, it is sure to be high interest since students are using living organisms. Caution: some students may have difficulty following the large number of written directions, while others may be upset by the Daphnia deaths caused by “polluted” environments.