Invent Circulatory Systems

By Steven Vogel, Duke University

Type of Resource Laboratory activity
Topic Circulation/respiration
Taxa Widely applicable
Organizational Level Systems
Estimated time to do activity 1 hour 
Background required/level any 
Role of activity in your course I used an early version for many years in the laboratory for an introductory biology course. That particular laboratory make especially great use of physical models--using them (as any kind of model can by used) as devices for abstraction and generalization, for seeing common functional features beneath the dazzle of biological diversity.  
What students might learn from this course or activity Concepts: the role of the various common mechanical elements in circulatory systems.  
Special tools, equipment or software needed The text describes the elements; the only unusual ones are the one way valves ("check valves"), which can be obtained from many scientific supply companies. Check under "connectors"--they should be small, in-line plastic pieces that look a bit like quick-disconnects.  
Safety precautions, possible permissions necessary Water tends to get on benchtops and floors, so lots of sponges and a mop or two ought to be on hand.  
Miscellaneous advice - pitfalls to avoid Much of the value of the exercise comes post-hoc, when students have to do some kind of written summing up. So don't fail to base some sort of written assignment on these otherwise casual explorations--some incentive to work and think systematically is generally needed.  
Frequently asked questions by students In the beginning course, we had some problems simply selling the pedagogical utility of physical models. Student come into biology courses expecting to fondle or disassemble organisms.  
Evaluation Results on examinations suggested that students had a better sense of circulatory systems as functional plumbing rather than as just a lot of names and places. We could count on proper answers to such questions as why no neural control of heart valves was necessary.  
Description Using simple components--flexible and glass tubing, T-tubes, squeeze bulbs, capillary or catheter tubing, one-way valves, and balloons, students self-discover the role of the various elements needed to make a pumped circulation. They can explore the operation of single- and dual-pump closed systems as well as open systems, and they inevitably (and valuably) encounter arrangements that don't work at all well.  
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