Improving dichotomous keys for undergraduate teaching

Abstract

University of Guelph undergraduate students have been struggling to independently identify macroinvertebrates using dichotomous keys in the Biology of Polluted Waters course (BIOL*4350). The course currently uses dichotomous keys that lack definitions of complex anatomical terms and illustrations that place features in the context of the whole organism. This results in taxonomic bias, whereby some macroinvertebrate families are ignored in subsampling, especially for Ephemeroptera (mayflies). This is of particular concern to biotic assessment of stream quality that uses Ephemeroptera as biological indicators. An updated dichotomous key for Ephemeroptera with illustrations and definitions of anatomical terms integrated within the text of the key was developed at the University of Guelph in Winter 2012. The generation of the key utilized a local macroinvertebrate collection, published literature and existing keys. The effectiveness of the updated key was tested against the BIOL*4350 key by comparing the number of correct identifications produced by undergraduate student volunteers using both keys. Additionally, the number of correct identifications by student volunteers who had previously taken BIOL*4350 (n=18) and those who had not taken the course (n=40) were compared. It was predicted that students who had previously taken BIOL*4350 would produce more correct identifications than students who had not. The new key had a significantly higher proportion of correct identifications than the old key (p<0.01). No significant difference in identification ability existed between students who had or had not taken BIOL*4350 (p= 0.53 and p=0.38). These results suggest the key developed through this investigation is a good starting point to develop similar keys and improve dichotomous identification in BIOL*4350 as well as other courses. Keywords: dichotomous key; undergraduate teaching; macroinvertebrate, Ephemeroptera