Phylogeny is the study of evolutionary relationships between organisms. It is best represented through diagrams called phylogenetic trees, which evidence relatedness between species and the presence of common ancestors. Teaching phylogeny can be often challenging, since concepts such as geological time and geographical changes on Earth are usually hard to comprehend. Unsurprisingly, there are several misconceptions around evolution, caused both by intuitive thinking and widespread misleading representations of evolutionary processes. Ballen & Greene (2017) argue that teaching about biodiversity using the traditional Linnaean rank-based approach (dividing organisms into Kingdom, Phyla, Class and so on) can potentially disseminate some of these misconceptions, since it omits evolutionary innovations and inaccurately portrays history. Instead, the authors defend the use of the clade-based approach, which teaches about biodiversity using phylogenetic trees.
But what are the most prevalent misconceptions in phylogeny and how to address them? Meir et al (2007) point out four major misinterpretations of phylogenetic trees, as follows: Firstly, students tend to not understand the spatial representation of the flow of time, mistaking species/groups on the left of the tree to be ‘older’ than the ones to the right. Secondly, students often think that tip proximity indicates relationship between species regardless of which clade they belong. Learners also tend to think that the number of nodes on a tree indicates how closely related they are. Finally, the absence of nodes represented by a straight line tends to be understood as a sign that species on the tip of that line did not suffer any evolutionary changes, being more similar to the common ancestor. Thanukos & MacDonald (n.d.) add to that list, claiming that students often understand evolution as progress, where some species are ‘more evolved’ than others. All these misconceptions must be addressed for the effective teaching of phylogeny. Diagnostic assessments can provide insightful information on what students think about the subject, and should be applied to identify the presence of misconceptions. Teaching can be most efficient when acknowledging and drawing from students’ prior knowledge, and several strategies for doing so have been compiled by Victoria’s Department of Education and Training (2017). Thanukos & MacDonald (n.d.) thoroughly describe each of the most common misconceptions and debunk them. The Understanding Evolution website (https://evolution.berkeley.edu) also offers some background information on phylogeny and valuable teaching resources.
Perhaps as important as efficiently addressing misconceptions is to provide students with the necessary context for their learning. Context-based science teaching might help students engage with contemporary topics, providing the link between school and their lives (Bransford et al., 1999 in Lenz & Willox, 2012, p. 551). Luckily or not, media coverage on evolution made the topic well known to the public, but also inspired several misconceptions about the theory. Zimmer (2010) points out that the widespread access to the internet added to the complexity of the situation, with an increasing number of websites advocating against science, and more specifically against evolution (e.g. “All about science”, a website that conceals from its readers its religious motifs. See http://www.allaboutscience.org). In this context, it becomes essential that science teachers are well informed and address external sources that influence students’ understanding of science. This may also contribute to forming scientifically literate citizens, a demand of the modern global community (Lenz & Willcox, 2012, p. 551). It is important to note that the Victorian Curriculum and Assessment Authority (VCAA) acknowledges the importance of tackling contemporary issues in the Biology curriculum, advising teachers on how to address these (VCAA, 2017).
With all these aspects of teaching Biology considered, the following learning sequence uses contemporary research in evolution to provide a context for teaching phylogenetic trees. Based on the evolution of medicinal plants, the resources provided here aim to facilitate understanding of evolutionary processes and some of the evidence of evolution. Students will build and interpret a phylogenetic tree and understand how it can be used to benefit modern society. Concepts of ethnobotany, the study of local plants and their practical uses based on indigenous knowledge, are also introduced, adding opportunities to teach Aboriginal perspectives and link this learning sequence to the topic of human evolution.
This learning sequence is outlined in two sections:
Section 1: Biogeography. This section is divided into two modules:
Module 1: How do geological changes on Earth affect living communities?
Module 2: What is biogeography?
Section 2: Phylogenetic trees. This section is divided into two modules:
Module 1: What evidence can we use to show relatedness between species?
Module 2: How to represent relatedness between species?
Links to the Victorian Curriculum
This phylogeny learning sequence is linked to the Victorian Certificate of Education (VCE) Biology Study Design (2017-2021). The resource focuses on Area of Study 1, Outcome 1 within Unit 4 (How does life change and respond to challenges over time?).
In Area of Study 1: How are species related? The key knowledge descriptors addressed within the unit are as follows:
Changes in biodiversity over time
Significant changes in life forms in Earth’s geological history including the rise of multicellular organisms, animals on land, the first flowering plants and mammals
Evidence of biological change over time including from palaeontology (the fossil record, the relative and absolute dating of fossils, types of fossils and steps in fossilisation), biogeography, developmental biology and structural morphology
Patterns of biological change over geological time including divergent evolution, convergent evolution and mass extinctions
Determining relatedness between species
Molecular homology as evidence of relatedness between species including DNA and amino acid sequences, mtDNA (the molecular clock) and the DNA hybridisation technique.
The use of phylogenetic trees to show relatedness between species.
Matthew Symonds and Uday Sundara tells us their stories and about their research in evolution and phylogeny.
Harley EH. 2009. Evolutionary and molecular taxonomy. In: Contrafatto G & A Minelli (eds). Biological science fundamentals and systematics, pp. 116-138. Encyclopedia of Life Support Systems, UNESCO, Paris.
Hillis, DM 1987, 'Molecular Versus Morphological Approaches to Systematics', Annual Review of Ecology and Systematics, vol. 18, no. 1, pp. 23-42.
Hubber, PJ 2014, Representation construction: A directed inquiry pedagogy for science education, in Inquiry-Based Learning for Faculty and Institutional Development, Emerald Group Publishing, Bingley, UK, pp.201-221.
Lenz, L & Willcox, MK 2012, Issue-Oriented Science: Using Socioscientific Issues to Engage Biology Students, American Biology Teacher, vol. 74, no. 8, pp. 551-556.
Meir, E, Perry, J, Herron, JC & Kingsolver, J 2007, College students' misconceptions about evolutionary trees. The American Biology Teacher, vol. 69, no. 7, pp. 71-76.
Saslis-Lagoudakis, CH et al. 2015, Evolutionary Approaches to Ethnobiology. In U. P. Albuquerque, P. M. De Medeiros and A. Casas (Eds.), Evolutionary Ethnobiology, Cham, Springer International Publishing, pp. 59-72.
Thanks to the following for contributing to the development of these sequences:
I am an evolutionary ecologist who is interested in trying to explain, from an evolutionary perspective, what has generated differences in behaviour, ecology, morphology (body shape) and physiology between closely related species. I use evolutionary trees to answer questions about why particular traits have evolved. Using this approach, I have investigated the evolution of traits as diverse as insect sex pheromones, reptile colour patterns, mammal metabolic rates, bird beak sizes and plant medicinal capacity. I have been a lecturer at Deakin University for 7 years, teaching evolution and statistics. I am also the editor-in-chief of the journal Evolutionary Ecology. Full profile
I am a PhD student at Centre for Integrative Ecology at Deakin University. My research interest is in understanding the evolutionary relationships of plant taxa. The current PhD research I am conducting is about using phylogeny to predict medicinal utility of Magnoliids, which is an Australasian spice clade. In this research I am trying to use chemical similarity between closely related taxa as an indicator to predict medicinal properties of Magnoliids. The fact that evolutionary related species exhibit similar characteristics fascinates me. Therefore, in my research work I try to explain medicinal properties of plants in the light of evolutionary biology.