Simple Cladograms

Hey all,
I am designing some cladograms and phylogenetic trees for my Grade 9 and 10 biology students. I’m teaching them about derived characteristics and such. I’ve already got the basic cladograms (animal phyla, chordata zoology, major plant categories, etc.) and am looking for more interesting cladograms with simple derived characteristics.

-The cladograms don’t have to look pretty-- I can redesign them
-I’m looking for derived characteristics that students could understand. E.g., “bird-shaped hips” could work, but not “promaxillary fenestra”
-Anything more niche (like, dinosaur cladograms! Or major bird family cladograms) would be great.

For instance: https://www.geol.umd.edu/~tholtz/G104/figures/104Thyreophora.png looks cool, but would be hard to make understandable for Grade 10. I’m looking for slightly more basic ones.

Thanks in advance for posting any phylogenetic resources like this.

Harrison

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Not sure if this qualifies as simple enough but it could be easily simplified for any level I think or you might be able to find similar pictures online:


(https://www.researchgate.net/figure/olvox-and-volvocine-algae-Simplified-cladogram-of-selected-volvocine-species-from_fig1_342610030)

It could be used to talk about two concepts: The progression from single cells to multicellularity within one example group (volvocine algae), and the progression from isogamy (all gametes look alike) through anisogamy to oogamy (egg + sperm). One of the neat things in this line is that the number of cells in the colonies doubles, going from 4 to 8 to 16 etc.

It could be combined with a lab/microscopy activity if your class is set up for that. I’m not sure where you’re located, but here in the US there are companies that sell prepared slides for these and even live algae. Volvox is really cool to look at, and Chlamydomonas can be used for demos/experiments, e.g. put them in a tube exposed to half light, half dark, and watch them all swim towards the light. If you get live Volvox, be aware that they often get shaken up and damaged during shipping, so you want to plan on having maybe two weeks or so to let them sit under a growth light and recover and regrow. Otherwise your students will only be able to observe broken bits and pieces rather than the mature balls of cells.

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Here’s another cool example from the plant world that could be spiced up with a hands-on class activity/demo if you have plants available (e.g. feeding Venus fly traps - always fun to do with kids).


(https://www.sciencedirect.com/science/article/pii/S0960982220305674#fig4)

I imagine this would probably have to be redrawn as a more simplified version though, cutting out maybe all but the key events towards carnivory unless you want to get into discussing whole genome duplications (WGD) and gene loss as the genetic factors driving plant evolution.

Are you familiar with Camincules? These were developed to teach about cladograms: https://online.ucpress.edu/abt/article/62/8/570/17670/The-Classification-amp-Evolution-of-Caminalcules
It can be a bit frustrating for some of the students that want “THE answer” but I have found the activity generates great class discussions.

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Check here: SimpleClade (guilfordgeo.com)

Be sure–please, please, please–to arrange the tree such that it doesn’t give the false appearance that evolution is a march from simple to complex (as this diagram does). One could put Pandorina morum on the far right and rotate the branches accordingly. When students see diagrams like this, they don’t consider that all the species in the tree are alive today (both simple and complex)–they think that the ones on the left are the ancestors to the ones on the right. They don’t consider that only some ancestral species produced descendants that are more complex. Many if not most of them produced descendants that remained simple and some complex species produced descendants that were actually simpler. When rearranged, that illusion goes away.

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Here’s one that I use as an example in my university class. For HS, I’d recommend replacing amphibians with snakes, and the synapomorphy could be loss of limbs. If pseudogene isn’t in their vocabulary, you can just say “broken” or “non-functional”. Mammals have within their genome a remnant of the gene that produces the major yolk protein.

This illustrates how a character (yolk) can be lost due to the earlier acquisition of another character (milk) that renders it (yolk) unnecessary. The origin of milk production meant that the yolk was no longer needed and when the yolk gene acquired a mutation, the mutant allele wasn’t removed by purifying selection and we retain that broken gene within our genome as evidence of our ancestry.

Note also that there isn’t an illusion of a march toward progress in this tree.

When having students examine these cladograms, I think the most important thing for them to understand is that they allow us to understand why groups of organisms share some traits but not all. The diagrams tell a story–and once the students understand that, the diagrams become more interesting. Birds have feathers but mammals don’t because feathers evolved after the divergence of birds and mammals. Birds and mammals share vertebrae because vertebrae evolved prior to the divergence of birds and mammals. But sometimes characters are lost. Mammals don’t have yolk, not because yolk evolved after the divergence of mammals, but rather because it was lost in the ancestor of living mammals (except Monotremes–sort of). Full story here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267822/

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Here’s an okay simplified cladogram I just sketched up of most major insect groups, based on the tree in this article.

The most familiar groups I left out were earwigs, stick insects, and lice. I can tell you where they would go too if you want.

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You may find useful an in-browser app I have made, darwintree.app (desktop only at the moment). The trees you can build with it only display images and taxon names, but you may be able to screenshot and add annotations as necessary. It uses the iNaturalist API so is unfortunately limited to the taxa represented on iNaturalist.

Here is an example tree (screenshot below): Common Florida Birds

It is very interactive and you can add and remove taxa, and the tree will maintain its integrity, automatically adding nodes where needed.

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That’s a really good point and one that always seems to come up in botany because all the plant cladograms pretty much look this way, too. Here’s the example from Wikipedia:

The misconception is reinforced by verbiage such as “lower plants” for bryophytes and “higher plants” for the seed plants. I think most botany texts nowadays try to get away from that, but the cladograms are pretty much all similar to the one above, no matter which book you open up. It results in questions such as: “If seed plants evolved from seedless plants, why do we still have seedless plants?” (The botany equivalent to: “If humans evolved from monkeys, why are there still monkeys around?”) Every biology teacher should have an answer ready for that one, but it may be prudent to address this misconception with the students whether someone pops the question or not. Maybe even give it to the students as a thought exercise and discuss.

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I wonder why people are compelled to draw trees like this? This tree only tells one story, the story of how flowering plants acquired their characters. In order for this tree to tell the story of plant evolution, it would need to have shared-derived characters on all of the branches! This is a flowering-plant-centric diagram.

One oversimplification (IMO) in this tree is that charophytes are not a single, monophyletic lineage (they’re like “fish” or “protists”).

Here’s an interesting article about the use of different phylogenetic visualizations

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I think it’s the human desire for simple explanations and a neat, straight-forward story. And yes, there are multiple issues with that cladogram in particular. I’m not sure it is resolved yet which group of algae within the charophytes is sister to all land plants, and I don’t think the bryophytes are fully sorted out yet either - the diagram uses one hypothesis of several. It’s also cherry-picking one example per branch for the seedless plants and missing a lot of plant groups, both extant (e.g. spike mosses and quillworts, horsetails and wisk ferns) and all the extinct groups that have come and gone. So basically it is taking a more complex tree and pruning out side branches until only a simple, linear narrative is left. Some of the characters popped up in several places (e.g. extinct seed ferns, some gymnosperms do double fertilization as well) but you wouldn’t know that from looking at this diagram. People like a simple story, I guess, but nature is more messy than this.

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This is great. I would perhaps not mix genetic and morphological characters along the branches. On the tree tips, one can add summary of the features present in each living species (e.g. thumbnails of feathers, vertebrae etc if this is to be improved graphically) so it is clear how different sets of features were gained, lost, or retained during the evolution of each lineage from the common ancestor (the root of the tree). The annotation of tree tips might be good place to introduce also a thumbnail for a “broken” gene.

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Not related to evolution but, if you aim at working with cladograms, what about doing a vegetation study using the Braun-Blanquet method and then analyzing data using an easy-to-use statistics sofware? For me it worked with grade 10 students.

PS: It is very complex but, at the same time, it is visually captivating and helpful to get an idea of the complexity of plant diversity in the world. It could make a good impression in a classroom:
https://www.researchgate.net/figure/Overview-of-The-phylogeny-of-angiosperms-poster-Full-download-available-from_fig1_322554838

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Yes, thanks for the reminder. I use the analogy of a mobile, like this art installation. A phylogenetic tree is like this, it can be rearranged. Imagine it’s blowing in the wind! It’s not as nice and neat as “simple to complex”-- it is simply a neat tool we can use to organize life!

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Thanks so much for taking the time to sketch this! Very helpful!

Amazing poster! Thank you

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What a cool website! I’ve been looking for something like this for a while! I love how it’s connected to iNaturalist. Thanks for making this and linking it

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That’s some amazing work! You should start a dedicated forum thread to introduce your website to the community.