||Designing your very own science experiment (for fun and enlightenment)
Author: Mark Stefanski
Overview: In this lesson, students will review the process of science and then design and carry out an experiment using pill bugs (isopods). Other organisms could be used in place of the pill bugs. Students are asked to address a specific question, test hypotheses, identify and describe variables, and make use of a control group. Students are asked to provide a written report that includes methods used, data collected, a summary and interpretation of the data, and a list of resulting questions. Students reflect on the process used by charting their pathway on the Science Flowchart.
- Science deals with the natural world and natural explanations.
- The process of science involves testing ideas about the natural world.
- The process of science is non-linear and iterative.
- The process of science involves observation, exploration, discovery, testing, communication, and application.
- In science, answering one question often leads to many more questions and additional research.
Grade span: 9–12
- A terrarium containing a population of pill bugs and/or sow bugs
- Containers of pill bugs and/or sow bugs for each pair of students plastic Petri dishes work well
- A copy of the Student Worksheet (www.understandingscience.org/lessons/pdfs/student_worksheet.pdf) for each student
- A copy of the Student Expectations (www.understandingscience.org/lessons/pdfs/student_expectations.pdf) for each student
- Variety of equipment that students may need to conduct their experiments
- A copy of the complex Science Flowchart (www.understandingscience.org/lessons/pdfs/complex_flow_handout.pdf) for each student
Advance preparation: Collect and maintain a pill bug population within the classroom.
Time: 2–4 class periods
Grouping: Pairs and whole group discussion
Teacher background: Both pill bugs and sow bugs (also known as woodlice) are terrestrial crustaceans and belong to the order Isopoda. They have a clearly segmented exoskeleton and paired jointed limbs. Woodlice need moisture because they breathe through gills, pseudo trachea, and are usually found in damp, dark places, such as under rocks and logs or under leaf litter. They feed mostly on dead plant matter. Woodlice can be kept in the classroom as long as you provide a few inches of natural soil (or potting soil) covered by leaf litter and a few pieces of bark (preferably oak). Although woodlice need moisture, be careful not to give them too much water. Simply spray the container often to keep things moist, but not wet. Add bits of carrot or apple for additional nutrition. For additional information see Teacher Resources below.
Teacher resources: For information on isopods:
Isopod, Pillbug, Sow Bug Information (http://insected.arizona.edu/isoinfo.htm)
Sow bugs and Pill bugs (http://crawford.tardigrade.net/bugs/BugofMonth17.html)
- Review the process of science introduced in a previous lesson such as Introducing the Understanding Science flowchart (www.understandingscience.org/lessons/introducing_flow_hs.html). Ask students to describe what they recall about the process of science. Key descriptors might include multifaceted, complex, non-linear, and even messy!
- Let students know that they will now have the opportunity to design and carry out their own experiments using an animal that they are probably very familiar with, but have not yet examined closely pill bugs. (Note: you may have a mixture of pill bugs and sow bugs, so explain accordingly.) But first, it will be necessary for them to make some initial observations before deciding what they want to investigate.
- Provide a container of pill bugs to each pair of students. Ask students to observe the animals and to make simple changes in their environments to see how they respond. Remind them that they are not to make any changes that might harm the animals. Have students record what they discover.
- After about 20 minutes of observations, provide each student with a copy of the Student Worksheet. Review the information with the students.
- Provide a copy of the Student Expectations for each student. Review the information.
- During the rest of the class period, students should discuss with their partners what question they would like to answer about the pill bugs and how they could design an experiment to answer that question. They should develop a working hypothesis and consider independent and dependent variables and the use of a control group. Let them know that they will be able to conduct their investigations during the next class period.
Note: You may or may not want to review their ideas prior to implementation.
- Use the next class period to conduct the student investigations. Students are asked to write a report as described in Student Expectations. Not all students will complete their investigations. You may want to provide additional class time to do so, or you can allow discussion based upon what the students have learned thus far.
- Have students present their methods and findings to the rest of the class.
- Provide an opportunity for students to reflect on their process see step 6 of Student Expectations.
- Share the process pathways developed from the student reflections.
Extension: This lesson provides a foundation on which students can develop a long-term investigation.