How stiff is a French fry? Teaching biomechanics to biology students

Mechanical investigations of biological materials are becoming increasingly important in the study of organismic and evolutionary ecology. Such studie s help to explain how and why organisms evolve and exist today, and address some questions of scale (e.g., how big can a tree or mammal grow?). These ideas and questions often intrigue biology students, but rarely are they ex posed to the measurements and principles underlying the mechanics of biolog ical structures. We present a simple technique to measure an important biom echanical feature of tissues, namely tissue stiffness or elastic modulus, t hat is used to determine the strength and durability of biological structur es. Using this technique on tubers of Russet Burbank potatoes (Solanum tube rosum), the elastic (or Young's) modulus (E) ranged from 1.08 to 14.15 MPa. This was well within the range reported for this plant material. We sugges t several experimental manipulations and provide results for one of these w hich can be easily conducted in an A-level or early university 3-hour teach ing practical (or laboratory).