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Keywords:

  • evolutionary diagrams;
  • tree thinking;
  • cladogenesis;
  • anagenesis;
  • evolution education;
  • diagrammatic reasoning

Abstract

The authors argue that some diagrams in biology textbooks and the popular press presented as depicting evolutionary relationships suggest an inappropriate (anagenic) conception of evolutionary history. The goal of this research was to provide baseline data that begin to document how college students conceptualize the evolutionary relationships depicted in such noncladogenic diagrams and how they think about the underlying evolutionary processes. Study 1 investigated how students (n = 50) interpreted the evolutionary relationships depicted in four such evolutionary diagrams. In Study 2, new students (n = 62) were asked to interpret what the students in Study 1 meant when they used the terms evolved into/from and ancestor/descendant of. The results show the interpretations fell broadly into two categories: (a) evolution as an anagenic rather than cladogenic process, and (b) evolution as a teleological (purpose-driven) process. These results imply that noncladogenic diagrams are inappropriate for use in evolution education because they lead to the misinterpretation of many evolutionary processes. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47:861–882, 2010