Classification: Putting Everything in Its Place

Classification lies at the very heart of science. Even a multitude of data cannot advance the discipline until appropriately organized and analyzed. Geologists developed the geologic time scale to divide Earth's 4.6-billion-year history; chemists use a periodic table to consolidate the properties of elements; and paleontologists and biologists employ taxonomy and cladistics to identify and determine relationships among extinct and living organisms. Classification depends upon pattern recognition, one of the crosscutting concepts of the Next Generation Science Standards (NGSS Lead States 2013), based on A Framework for K-12 Science Education (NRC 2012). Our natural world tends toward disorder, so recognizing a pattern can be "the first step to organizing phenomena and asking scientific questions about why and how the patterns occur" (NRC 2012, p. 85). Classification systems can evolve as the scale of observation changes and more scientific information and detail are uncovered. This evolution reflects the nature of science (NOS), since the NOS Matrix includes "Scientific Knowledge Is Open to Revision in Light of New Evidence" and "Science is a Human Endeavor" (NRC 2012). Historical case studies illustrate these characteristics of the nature of science and also fascinate our students (Clary, Wandersee, and Carpinelli 2008; Clary and Wandersee 2011). Accordingly, we approach patterns by first telling the story of the Linnaean classification system, before students undertake activities to find patterns and develop--and justify--their own classification systems. Linnaeus: Observation and classification Carl Linnaeus (1707-1778; portrait, p. 31), known as the father of taxonomy and a founder of ecology, is credited with devising the formal system for naming species. He introduced the binomen, or "Latin name" system, identifying an organism with a genus name and, within the genus, a species name. Species, the most exclusive category of classification, are those organisms with similar morphologies that can interbreed and produce fertile offspring. For example, Panthera tigris is the binomen for the tiger: Panthera identifies the cat genus, which also includes the leopard and the lion, and tigris the particular species of cat. Linnaeus first applied this system of nomenclature to plants, thereby revolutionizing botany and founding plant taxonomy. Later, he applied it to animals as well. We researched this pioneering scientist through historiographic methods (Howell and Prevenier 2001), including visits to Linnaeus's university, garden, home, and farm in Sweden, and by studying his work through historical documents and artifacts. Introducing students to Linnaeus and the history of classification piques students' interest in the nature of science and the way science progresses (Matthews 1994). Observational beginnings. Carl Linnaeus, nicknamed the Little Botanist at school, acquired his passion for plants from his father, Nils, a minister and amateur gardener. Nils decorated his son's crib with flowering plants, and when the baby seemed unhappy, gave him a flower to play with. At age four, Carl was reportedly impressed by his father's remarks about the uses of neighborhood plants in their community of Rashult in southern Sweden. His father taught him plant names but, after young Carl forgot some of the names, warned he would stop teaching him if this continued. So Carl redoubled his efforts to learn about plants, beginning his habit of careful observation and attention to detail. Ultimately, Linnaeus would name about 12,000 of the world's plants over his lifetime. Integrated investigations Linnaeus became a professor at Uppsala University in the Swedish town of Uppsala. He was popular with students, largely due to his great enthusiasm and novel ways of teaching. He didn't confine his research to a university laboratory. At his home (Figure 1), located next to a large teaching and research garden, the ground floor served as family living quarters, while the upstairs was devoted to a scientific center with lecture room, library, study, and rooms for botanical collections. …