Natural variation, including the continual selective pressures that lead to speciation, is one of the more dynamic aspects of biology. However, traditional instruction on the topic is often passive in nature, leaving little opportunity for scientific inquiry. In this laboratory exercise, we use a statistics-based, guided-inquiry approach to engage students in natural variation. Students are introduced to speciation and classification by using a dichotomous key to identify various common local trees on the basis of leaf characteristics. Once the students have learned characteristics useful for identification, they are given two leaf samples, a sugar maple and an "unknown." They are asked to choose characteristics and collect quantitative data in order to determine whether the unknown is a sugar maple. Before data collection, students form hypotheses related to the identity of their unknown, followed by statistical comparison of means to support or refute their original hypotheses. In this way, students gain an appreciation for the activities undertaken by taxonomists that are related to natural variation and classification.
Key Words: Variation; inquiry; taxonomy; systematics; student engagement.
The general intent of the introductory biology laboratory is to reinforce basic biological concepts while teaching skills that are necessary for conducting science. Traditional laboratory exercises have been expository or "cookbook" in nature rather than inquiry-based. The diversity of life and its classification, including the continual selective pressures that lead to speciation, has been no exception. Although the topic is one of the more dynamic aspects of biology, laboratory exercises have tended to be "show-and-tell," presenting students with lists of characteristics that distinguish earthworms from planarians, green algae from conifers, and bacteria from archaea. During lab activities designed to coincide with lecture presentations, students are typically shown representative examples of taxa, often preserved specimens, with the occasional dissection or live specimen. Seldom is the scientific method used, and so there is very little opportunity for scientific inquiry.
While there is evidence that inquiry-based labs result in increased understanding (e.g., Lord & Orkwiszewski, 2006; Rissing & Cogan, 2009), it can be difficult to implement them (e.g., Sundberg & Armstrong, 1993; Brainard, 2007). The activity presented here is an intermediate approach, called a "guided inquiry" by D'Avanzo (1996) and Grant and Vatnick (1998), in which students are given a research question and resources, but they design and conduct an open-ended investigation. This method not only gives the students some ownership and experience with the scientific method, it also provides guidance and is somewhat easier to manage logistically. We use a statistics-based, inquiry approach to engage our students in natural variation and classification, in this case by learning to classify species of common local trees on the basis of leaf characteristics. Once the students have identified characteristics useful for classification, they are given two leaf samples, a sugar maple and an "unknown" sample. They are then instructed to use the scientific method to address the following question: Is the unknown a sugar maple? Before they collect data, the students form hypotheses related to the identity of their unknown. They then choose characteristics for comparison, collect quantitative data, and conduct statistical comparison of means to support or refute their original hypotheses.
This lab is designed to be completed during one 3-hour session of our introductory biology course for majors. It addresses many of the central themes of biology outlined in BIO2010 as critical for understanding the unity and diversity of life, specifically those concerning heritable genetic variation and speciation (National Research Council [NRC], 2003). …