Figure 3

Sample student trees. The students’ work is shown in black and white. The individual animals in completed surveys were highlighted by the investigators to facilitate scoring as follows: vertebrates are blue (mammals) and green (non-mammal vertebrates); invertebrates are yellow (arthropods) and pink (non-arthropod invertebrates). Individual surveys are discussed in the text. Each of the drawings in this figure exemplifies several important features from our rubric. Key features are highlighted below; see text for details. (A) This drawing shows a branching structure and a single level of hierarchy; it also shows a single common ancestor. (B) This drawing is not a single tree and extant taxa are sometimes at internal nodes; furthermore, it appears to show hybridization among groups. (C) This is a correctly structured tree. (D) This drawing includes a loop or network where there are multiple paths from one organism to another. (E) This drawing has essentially none of the important features of a phylogenetic tree.