Angela Cruise
Product Development

January 2017

Predicting and explaining patterns of interaction that organisms have with each other and with their environment is a key component of the middle school Next Generation Science Standards* (MS-LS2-2). In this investigation, students determine millipedes' preference for a bright or a dark environment by giving the organisms a choice between a clear chamber and a black chamber. Prior to testing, students formulate a hypothesis based on their knowledge of millipedes' natural habitat and behavior. Students then conduct a true behavioral choice experiment, analyze their results graphically, and explain the concepts behind these results.

Materials

• Large Choice Chamber Apparatus (with central tunnel, gates, 1 clear chamber, and 1 black chamber)
• Millipedes
• Large Holding Habitat
• Small Container
• Stopwatch or Timer

Procedure

1. Using what you know about millipede habitat and behavior, write down a hypothesis that predicts whether millipedes will choose the bright (clear) or the dark (black) choice chamber habitat.
2. Use your small container to collect 3 millipedes from the large holding habitat.
3. Make sure all the gates of the choice chamber are in the closed position. Gently place the millipedes in the tunnel, the center portion of the apparatus.
4. When you are ready to begin testing, start the timer and remove the gates blocking the millipedes' access to the clear and black chambers.
   Caution: Do not remove the gates that don't have chambers attached.
5. Every minute for 10 minutes, count the number of millipedes in each chamber, and record the results in the Two-Way Choice Data Table. To simplify the data collection process, if a millipede has most of its body in a chamber, it should be counted as in that chamber.
6. After 10 minutes of data collection, remove the choice chamber lids, collect the millipedes in your small container, and return them to the large holding habitat.
7. Graph your results in the Data Graph using a stacked bar graph format. What do your results tell you? Is your hypothesis supported? How do your findings make sense when you consider the natural habitat and behavior of millipedes?

*Next Generation Science Standards® (NGSS) is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.