Tree of Life- any major errors?

Hey all,
I’ve been working on a Tree of Life that covers the major clades in Zoology all in one cladogram. This is for my high school level Biology class, so it’s not intended to be as detailed and nuanced as maybe a college-level curriculum. I’ve told my students that every cladogram has exceptions (e.g., not all fish lay eggs, etc.). I know so many of you are experts! Could you give me any feedback-- do you see any glaring errors or problems with this tree of life? Or perhaps, certain traits that I missed that would be beneficial to add?

You can view the Tree of Life PDF here

Here is an image preview:

Thanks so much for your feedback! As you can see from the watermark, this is a preview, and in the future I will probably be selling this kind of thing on TeachersPayTeachers, so I appreciate you not downloading it and re-uploading it somewhere else. Thanks!

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Looks great! The only major thing I can see is to do with paraphyletic groups, especially groups that used to be considered monophyletic (if you don’t understand those terms, don’t worry).

So see how you’ve got reptiles leading to birds, because birds are actually a type of reptile? It’s the same with crustaceans and protists. Animals, plants, and fungi all essentially came from within protists, and having them split off early like that doesn’t make much sense. For example, looking at the two protist examples you’ve got there, they’re not actually closely-related at all - malaria is actually next to the plants, and Amoeba splits off just before fungi but after plants.

It’s the same with crustaceans - insects have come from within crustaceans, and so they’re actually a type of crustacean. In both of these cases I’d recommend just to do something similar to what you’ve done with reptiles and birds, and that would solve it!

Other than that I can’t see any errors in the structure of the branches, although the three-way split of placental mammals is a little ambiguous and potentially confusing. Better to change it into two sets of double splits, in which case carnivorans (Cheetah, Wolf, and Seal) are closely-related to ungulates (Cow, Pig, Deer, and Whale), and the Euarchontoglires (Human, Ape, and Chipmunk) would split off from them first.

Two further things that aren’t essential for accuracy, but are good to know and include:

Firstly, be careful of presenting a tree of life as a sort of ‘hierarchy’ like this, as it can give the impression that organisms lower down are ‘less evolved’, and that somehow we humans are ‘more evolved’. I’m sure that wasn’t your intention, but when impressionable students see this, they may get the impression that organisms at the top of the tree are more advanced, or that evolution was ‘aiming’ to create something like humans. An easy way to combat this would simply be to flip it upside-down! Or alternatively you could add other organisms in if you wanted, which could be valuable if you want to talk in more detail about certain animal groups.

And secondly, a key thing is to aim for consistency in your choice of names and labels. Looking at all of your labels here, there’s nothing incorrect that I can see, but why do some of them have a rank label and others not (e.g. why “Class Boned Fish” but just “Jawless Fish”), and why are some scientific names and others common names (e.g. why the scientific name “Eukarya” rather than the common name “Eukaryotes” but the common name “Plants” rather than the scientific name “Plantae”)?

Those are my two cents at least, but overall it looks great! I wish I had learnt this stuff when I was in high school

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I agree with all of Matthew’s points and have nothing more to add.

I am curious, though, did you create the diagrams yourself? I say this because if you want to sell it you need to be careful about the kind of licenses the diagrams are under if they were made by others.

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I also agree with @matthew_connors but want to put a bit more emphasis on the visual aspect of these depictions. In this paper (unfortunately paywalled) - Redrafting the Tree of Life on JSTOR - and in many of his books, Stephen Jay Gould stresses that as primates, humans are very visual creatures, and hierarchical depictions convey information that is perhaps not intended. For example, the two images are the same size, but one only includes vertebrates. Without meaning to, this conveys the sense that vertebrates are somehow equal to all the rest of non-vertebrate life. In spite of non-vertebrates being more numerous and equally complex to vertebrate life. I’m not sure how Gould suggested the visual ‘tree’ should be changed, but it might be worth while taking a look at some of his work.
EDIT You may also want to give the two Kingdoms Plants and Fungi a bit more attention than a single branch off the main stalk.

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And note that although insects probably evolved from crustaceans, this is not true for arachnids, so you should maintain arachnids as a distinct branch.

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You can access a non-paywalled version of the paper at https://sci-hubtw.hkvisa.net/10.2307/987248.

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Thank you very much! I had begun to look through some of the collections of essays he has written, but had not stumbled upon it.

Agree with what @matthew_connors has said, but there is one more paraphyletic group that he didn’t specify, namely Class Boned Fish. I think this one could be fixed more easily by just changing the name to Class Ray-Finned Fish instead of changing the structure of the tree, since Ray-Finned Fish are monophyletic, and comprise >99.99% of Bony Fish.

I would also add that because gills were present in the ancestors of terrestrial insects and arachnids but lost during the transition to land, the character “Gills” should be placed on the branch leading to Phylum Arthropods instead of on the branch leading to Crustaceans (although since gills have been independently acquired in many phyla, maybe best to just leave them off).

Another character state that is in the incorrect position is “Lungs”; the character should be placed on the branch leading to the Boned Fish-Tetrapod split, not the Tetrapod branch. Lungs already existed in the ancestor of Ray-Finned Fish, but were secondarily modified to function as buoyancy organs (swim bladders) in most Ray-Finned Fish. I think there is a common misconception that the lung is derived from the swim bladder (in fact, this is what Darwin believed, and seems the more “logical” progression), but it is actually the other way around; many of the primitive freshwater non-Teleost fish alive today still have dual-functionality in their lungs/swim bladders, and some of them rely entirely on gulping air for respiration. If you moved the position of the “Lungs” character, you could also add “Lungs modified into swim bladder” as a character for Ray-Finned Fish.

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Why no Kingdom Chromista?

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I see you have an Aardvark at the base of the tree for placental mammals. This is probably appropriate although maybe a shrew or hedgehog along side them would illustrate the point that insectivores are probably the ancestors of all placental mammals

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Thank you so much. I struggle with balancing a phylogenetic tree and a taxonomic one. Sometimes the phylogenetic aspects cause students to really get confused with their mental schema and categories. I’m trying to show the evolutionary relationships, BUT… I’m also using the cladogram as a concept map to show which different traits describe different taxa. Because every cladogram is a hypothesis, and in 50 years our tree of life will probably be different in some ways, I am comfortable to some degree to let some nuances slip by for the high school level if it means that they can get the bigger picture better.

From what I’ve understood, it seems that I could say “insects came from crustaceans” but not that “Insects are a type of crustacean” (correct me if I am wrong). I will edit the arthropod tree to make it more accurate. I’ve also change the mammals accordingly.

Yes, I actually go over before this a lesson on how to properly read cladograms. In it, I show them a tree of life with a beetle at the top, and with humans to the side. I show them the tree is flexible and isn’t trying to place humans at the very top.

Thanks, yes I was trying to be consistent and the Eukarya slipped my notice.

I appreciate your thorough feedback a lot!

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Thanks for your concern. Every diagram I use is either drawn by myself or is a public domain image I have downloaded from Wikimedia or Flickr. All the public domain images I’ve downloaded were drawn before 1920 and are usually scans from old books in the 1800s. From my understanding of Public Domain, we can use them freely, even for commercial purposes (please correct me if I am wrong).

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Thank you. I’ve changed the name to Ray Finned Fishes.

Regarding the gills and lungs-- yes, this is hard to explain this nuance at a high school level. I didn’t know about the swim bladder/lung explanation there, so thank you.

Yes, the gills is a hard trait for me to figure out how to present. I thought gills would be a good trait that helped define crustaceans and show their uniqueness. Is there another trait that is a better unique descriptor of Crustaceans? And one that isn’t too hard to explain to high schoolers?

Thanks so much for your insight!

Hmmm… it was my understanding that the Aardvark and the elephant shrew were Afrotherians closer to the base of the placental mammal tree, and that hedgehog and shrew belonged to Eulipotyphla farther up the tree, closer to bats and ungulates. Am I missing something?

Yes, this is a good point. I know chromista is now considered a major kingdom (even though I was not taught it in high school…). In the tree, I generally put “protists” as a side branch and avoided calling them a kingdom like the plants, fungi and animals. I know protists are spread everywhere in between the fungi and plants phylogenetically, but for the sake of an initial simplicity, I just want my students to know that protists are the category of thing that aren’t in the animal, plant, and fungi kingdom. I understand that malaria would belong to Kingdom Chromista, and Amoeba to Kingdom Protozoa. This is more of a “thought tree” than a “100% up-to-date phylogenetic tree.”

It is somewhat based on this grouping: https://darwintree.app/b/My_Tree-3kec-PRo-we4-hTv-ws4-11zW-1-1uwH-cg6-cgO-B0u-1iZI-1XN1-hw1-y8I with the Chromista and protozoa combined.

I guess if I wanted to offer this as a resource to other teachers, I might have to make that more accurate. If you think this is a gross error and that 9th graders should learn the difference between Chromista and Protozoa, then please let me know!

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Would this be a correct and nuanced description of gills?

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This is too similar to the “great chain of being”, giving the illusion that there has been a march of progress from certain “lower” groups to “higher” groups (ultimately humans). Please DO NOT give this to teachers to use because this way of thinking about evolution is false. Taxa which are extant (alive today) all need to be at the top in order to prevent the tree from giving students this illusion of progress. If you insist of a tree shaped like this, please at least put birds at the top and the mammals as a branch off to the side (swap birds with mammals). And swap vertebrates with arthropods in the 2nd tree. And move bacteria up a bit so they’re not totally at the very bottom. Better yet, consider using landscape format and place bacteria and archeae on the left and eukarya occupying the right 3/4 of the page (with vertebrates positioned closest to archeae), and arthropods occupying the prominent top/central position. Same idea for the vertebrate tree. You’ll see that it gives an entirely different perspective even though both are correct representations of relationships.

I also recommend being consistent with your placement of taxa names (such as classes)–you have some at base of lineages and some at tips of lineages. Put birds, T. rex, and lizards/snakes on three branches and place Class Reptiles at the base of that lineage. Frogs and salamanders on two branches with Class Amphibians at base of that lineage. Same goes for all the other lineages.

Viruses should not be on a branch of the tree at all (not even a dotted branch)–they most likely don’t have the relationship with other species that your tree depicts.

Five fingers evolved in early vertebrates (it’s an ancestral condition of vertebrates, not a shared-derived character of primates). The endoskeleton of vertebrates and echinoderms are not derived from the same ancestor (I don’t think), so it’s misleading to have the one endoskeleton character basal to those two groups. If it’s important to keep it, I’d suggest placing it basal to both groups separately.

Did animals evolve from an ancestor that had a cell wall? I don’t think so. I think the ancestor of fungi evolved a chitin cell wall independently of the cellulose cell wall of the ancestor of plants…and fungi, plants, and animals all evolved from an ancestor that lacked a cell wall. So I’d remove “loss of cell wall”.

Your tick marks are showing two different kinds of things–and that’s confusing. Most of them are shared-derived characters that evolved along the lineage where the tick marks are except for things like “heterotrophic only”. That’s not a shared-derived character of the opisthokonts–it’s an ancestral character. Heterotrophy is the ancestral condition of all living organisms. Because of the complexity, I might omit those aspects from the tree. One tree can’t show everything.

Everything alive today needs to be at the tip of a branch, not along a branch leading to other things. Either omit the aardvark and chipmunk entirely, or include a little branch leading to them. Actually, since it’s very mammal-centric, omit aardvark and chimpmunk and flesh out the other lineages (i.e. sharks and rays on two separate branches) and have ungulates and whales on two branches with carnivores basal to them and primates basal to carnivores).

“DNA in chromosomes” basal to eukaryotes is misleading because bacteria have DNA organized into chromosomes also. Archaea are noted for species which are extremophiles–but not all of them can. And other groups include extremopiles also. It’s not really a shared-derived character.

Regarding “reptiles”, that’s a tricky one. I’m not sure how settled biologists are in using the taxonomic categories Class Reptilia and Class Aves. Our major college freshman biology textbook has stopped using Linnaean ranks altogether–but you probably need to go with what’s in the major high school textbooks.

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Yes, great.

I’d avoid basing your tree on the one linked to there. It has a few problems.

Students do need to know what “protists” refers to–a historical group which was created due to a lack of understanding about their true relationships–since they’ll likely encounter the term at some point. But it’s challenging to know how best to handle it in 9th-grade learning material beyond that. In a tree for students at this level, perhaps it would be best to place three or four “protist” lineages at various points throughout the tree. That way they can see that it’s not a true evolutionary group based on a shared common ancestry. For example, amoeba (“protist”) could go basal to fungi/animals. Volvox (“protist”) could be a lineage branching off of the plant lineage. Malaria would then be a lineage branching off basal to the split of Volvox and plants. Giardia (“protist”) or Euglena (“protist”) could go on the branch where amoeba and malaria currently reside. Here’s a relatively reasonable phylogeny upon which these recommendations are based.

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The ancestor of placentals may have fed on insects, but there is no longer a taxonomic group called insectivores.

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