Nanobes - Are they alive?

Lab Summary This case-based guided inquiry lab challenges students’ conceptions of what it means to be alive. Prior to lab students are confronted with a brief case study involving disagreements among scientists about whether nanobes should be classified as alive.  At the start of lab students are asked to determine whether a number of common “things” (potatoes, bean seeds, bare twigs recently cut from a bush etc…) are alive.  Disagreements that emerge among lab teams are addressed by asking students to develop a protocol to test their "life" hypotheses, by looking for signs of metabolism (CO2 uptake or release). The lab explores/challenges student’s conceptions of life, and gets them to consider how a scientist might determine whether or not something is alive by introducing students to aspects of experimental design (forming a hypothesis and experimental prediction, measurements of biological processes, negative controls, use of descriptive statistics, graphing).  The lab also exposes students to the hardware and software which will be used in future labs as they explore aspects of metabolism.

• To develop a deeper understanding of the properties of life.

• understanding the conceptual relations between a biological process and a quantitative measure of that process.
• developing and justifying an experimental hypothesis and prediction.
• designing an experiment with appropriate positive and/or negative controls
• recording, organizing, summarizing (descriptive statistics and graphing) data in a MS Excel spreadsheet.

Learning Theory & Pedagogy

This lab challenges students' understandings about the nature of life (What is life?), and how we might determine whether or not something is alive.  Why challenge students' conceptions?  Learning theory suggests that students hold tightly to their understanding (often misunderstanding) of the world.  To meaningfully change a student’s conceptions, they must be put in a situation that challenges his or her current conceptions and creates cognitive dissonance.  This simply means that students come to realize that a new understanding is needed to explain that which simply does not fit their current understanding.   What is most important is that this dissonance is fostered in a way that is not threatening to individual student, and which evokes a renewed sense of wonder. 

Although the question of whether something is alive or not is seemingly obvious, students typically disagree about whether or not common things they have had direct experiences with (a potato or apple seed) are alive.  Moreover students also discover that scientists themselves often disagree about whether or not things we find in nature are alive (i.e. viruses and nanobes).   The cognitive dissonance created in the early stages of this lab combined with students' intrinsic interest in question related to the nature of life (Does life exist on other planets? How can life exist in seemingly inhospitable places such as around hot springs, undersea hydro-thermal vents, and miles below the earth’s surface?).  Fortunately we don’t need to go to these extreme places to challenge students thinking about what defines life.  There are many things around us in our daily lives which generate some uncertainty among students as to whether or not they are alive. 

This lab is also meant to directly confront the following common misconceptions that students have about basic tenets of science
•    Experiments “prove” (rather than provide support) a hypothesis.
•    Only professional scientists are capable of doing science, or making good decisions about science related issues.
•    Science is a collection of facts and ideas that must be memorized.
•    Scientific knowledge never changes...it yields unchangeable truths about the world.
•    If variable A increases with variable B, then this alone is evidence of causation…A causes B to increase.  (Ignoring the importance of experimental controls.)

Instructional Resources

• An instructor guide which provide lab instructors with pre-lab preparation instructions, suggested materials, learning theory and pedagogical suggestions.
• Instructor PowerPoint presentation which challenges students' ideas about the nature of life and prompts further discovery.

• Vernier data logger and gas sensors (O₂ and/or CO₂)
• Team computer with access to MS Excel