Table 4. Definition and explanation of each type of reasoning with trees listed in Figure 1.
ReasoningDefinitionExplanation
CladisticsCladistics is an approach commonly used in biology to make assumptions about the evolutionary history of organisms. In detail, cladistics uses patterns of synapomorphies (i.e., traits of a common ancestor that were inherited and are shared by a group of taxa) (Novick et al., 2010) to infer the order of lineage divergence of organisms in evolutionary history. The principle of parsimony is typically adopted when biologists use cladistics (Goldsmith, 2003; Henning, 1966). For teaching in K-14 classroom, cladistics, as a type of reasoning with trees, is simply defined as an approach used to classify organisms based on whether the organisms share common characteristics inherited from their most recent common ancestor.If an evolutionary tree is constructed by using synapomorphies to show the lineage divergences of organisms, it means cladistics was used to construct that evolutionary tree. An evolutionary tree which was constructed without using synapomorphies to show the lineage divergences of its entities on the tree is recognized as not based on cladistic reasons.
HomologyIn biology, homology refers to any of a group of organisms’ traits that were derived from a similar trait in an ancestor they shared (Hall, 2012). These traits are called synapomorphies, which can be morphological, molecular, or behavioral characteristics shared by a group of taxa as a result of their inheritance from a common ancestor (Novick et al., 2010). Homology involves reasoning that is focused on the historical nature of homologs to understand biological phenomena (Ereshefsky, 2012).All the trees showed homology because the organisms that shared similar traits derived from a common ancestor were clustered together on a branch of the tree.
HomoplasyIn biology, homoplasy refers to the presence of any similar traits that are shared by different organisms but that were not derived from the similar trait in a common ancestor.When two entities on an evolutionary tree show similar traits that came from different lineages, the tree reveals homoplasy. Convergent evolution explains why homoplasy occurs.
ChronologyChronology refers to the science of ordering events by occurrence in time.Rooted trees show chronology because the roots represent the most distant ancestor in time. Unrooted trees do not show complete chronology, or the chronology is unclear because the most distant ancestor in time has not been indicated (Kong et al., 2016).