Lab Summary This lab begins with a relevant, real-world case study adapted from the a case published by the National Center for Case Studies Based Teaching in Science (https://sciencecases.lib.buffalo.edu/cs/). This case on hyponatremia engages students in this lab by providing an interesting, student-centered context for learning about osmosis and diffusion and its connections to body function.  This initial stage of the lab sets the stage for this inquiry by allowing students to explore their initial conceptions about how altering solute concentrations in the fluids surrounding cells would influence the movement of water across cell membranes.  After the initial “test-run” experiment the class decides on an independent variable to test its effect on the movement of solute/solvent over time.  Using resources provided in the lab manual individual teams and the whole class work together to pose a class question and develop the appropriate experimental design.  Individual teams gather class data and then analyze these data and draw conclusions.

Conceptual Learning Objectives - Upon completion of this lab, students should be able to

• explain how solute concentration, particle size, membrane permeability influence osmosis and diffusion.
• explain why maintaining homeostasis with regard to osmotic balance is crucial to organisms.
• understand how conductance sensor can be used to measure ion concentration in a solution.
• develop and justify a biologically relevant hypotheses for why a particular treatment would affect the progress of hyponatremia.

Scientific Skills - In the context of this lab students will practice and receive feedback on

• understanding the conceptual relations between a biological process and a quantitative measure of that process.
• developing and justifying an experimental hypothesis and prediction.
• identifying dependent and independent variables in an experiment
• designing an experiment with appropriate positive and/or negative controls
• recording, organizing, summarizing (descriptive statistics and graphing) data in a MS Excel spreadsheet.
• developing statistical null and alternative hypotheses.
• using inferential statistics (a t-test) to analyze data and draw conclusions regarding an experimental hypothesis.
• exploring the importance of  replication and repeatability in scientific experiments.

Learning Theory & Pedagogy

The more traditional highly guided & context-independent science lab model typically uses scientific methods but these kinds of labs usually prompt students to follow (often mindlessly) a set of science instructions, which guide students through a process of finding out about something, for which “an answer” or outcome is preplanned and already known.  Moreover, the lack of initial student-centered context for the lab exploration sets up an unengaged lab experience that is more akin to blindly following a cookbook recipe, and like a recipe, is often thought to have failed if the expected results don’t materialize.  This more “cookbook” approach to science labs does little to help students develop literate conceptions of the nature of scientific knowledge (validity, tentativeness, limitations, importance of experimental design features, applications...).  Students are likely to be more invested in a science lab if there is an initial lab context that is centered around student interests and experiences and they are allowed to make critical decisions about the design and execution of the experiment.  So the focus of this "practicing inquiry" lab is to build on students understanding of how science is done, by guiding them through some aspects of doing science, but leaving many of the decisions (hypothesis formation, aspects of experimental design and predictions) up to the students.  This elicits student ownership of the experiment, generating intrinsic interest in the outcome, while also giving them practice applying important biological concepts and practicing designing and interpreting experiments.

Instructional Resources

• An instructor guide which provide lab instructors with pre-lab preparation instructions, suggested materials, learning theory and pedagogical suggestions.
• Lab manual appendices that teach students about experimental design, descriptive statistics, graphing and inferential statistics using MS Excel.
• An engaging pre-lab case study on hyponatremia adapted from the National Center for Case Studies Based Teaching in Science (https://sciencecases.lib.buffalo.edu/cs/).

Required Materials

• Vernier Data Logger and Conductivity Sensor
• Students team computers with access to MS Excel.