The most represented principles in students' answers were those of phenotypic variation [V], connecting the scales of organisms and populations, and of differential fitness [F], connecting organisms to their environment (Fig. 5, pretest).
If the student drew a network, a distinction could not be made between invertebrates and vertebrates because there are multiple pathways connecting organisms and the survey was not included in this part of the analysis (Figure 3A,B,D,E).
Almost all the students (95%) used branching morphology in their post-surveys and about 90% of students connected all organisms in one cohesive tree.
From this point of view, phylogenetic reconstruction, especially of reticulation events that connect divergent organisms, is often considered appealing.
These results indicate that when using sets of genes that are known to be less frequently transferred, as may be case for ribosomal proteins, a supermatrix approach is preferable, whereas for datasets where cryptic highways of gene sharing may connect divergent organisms, supertree approaches such as quartet decomposition may be more accurate.
Two methods are generally used to measure the adhesive strength of invertebrate larvae: direct measurement with a force transducer connected to the organisms and indirect measurement with a water flow used to dislodge the organisms.
All organisms connected: Because all life descended from a single common ancestor, a correct tree should show connections between all organisms.
Student trees were scored as having all organisms connected (Figure 3A,C,D) or not (Figure 3B,E).
Specifically, we observed significant improvement over the semester in students drawing a tree with all organisms connected, placing extant species at the tips of branches, including a single common ancestor and using branching morphology.
