\ Visualizing Evolution: Venn Diagrams as Cladograms

Tuesday, August 19, 2008

Venn Diagrams as Cladograms

For whatever reason, this morning I was remembering back to 10th grade Biology class, and the frustration I felt when trying to correct a classmate who said "well, bees aren't animals, right? They're insects!" I tried in vain to explain how different groups fit within the group called "animals," but I believe the moment I gave up was when she said that "well, not all mammals are animals, because humans are mammals but we're not animals." *sigh*

Perhaps I should have whipped out some paper and sketched an evolutionary tree. But trees are confusing to people who are new to the idea of cladistics. However, there is another option, and that is the Venn Diagram.

Now, Venn Diagrams are usually reserved for data sets that intersect. With cladistics there are no intersections (unless you get into hybridization, which I'm not going to do), but rather, data sets embedded within other data sets. They're also not the most efficient way to show clades, especially if you want to include a lot of groupings, but they can be excellent in introducing the idea of grouping.

Case in point, here's one by Ray Troll explaining why we are fish:
This view is also rather humbling, to see our group "Hominids" so tiny and so deeply embedded within so many stacking groups. Primates to mammals to amniotes to tetrapods to lobe finned fish to bony fish to vertebrates to chordates. We are all those things because we are grouped within them.

So how does a Venn clade compare to a normal branching one? Here's an example found here, at the website for the Universidad Autonoma de Madrid:
And here another example from an entry on Clades from the blog Evolving Thoughts comparing a branching clade to a Venn diagram.

These two illustrations also demonstrate a couple of important ideas in cladistics. The first is the idea of a paraphyletic group, represented here by both "Invertebrata" and "Reptilia." The other is a polyphyletic group, represented by "Homothermia" and "Crossopterygii."

And since 1. I'm already on the topic of Venn diagrams, and 2. I don't make fun of intelligent design nearly enough on this blog, and 3. I've been on a roll lately making trouble with people, I leave you with this!:

14 comments:

Kumah said...

That's not true because if it was then how come people don't randomly give birth to fishes? :o

Anonymous said...

I remember picking Heid up when she was about eighteen months, holding her toward the ceiling and saying you cute little tetrapod you. Now I see from the cladistic diagram that I was accurate.
Dad

Heidi Richter said...

^^^

Did you really do that?

Well, I guess I was paying attention! : )

Anonymous said...

I think your retarded. We are not freaking fish.

Heidi Richter said...

Oooh, finally! I've always wanted a flaming comment from an "anonymous" reader! Maybe if you really stood behind what you say, you'd have the courage to use your real name!

Anyway, I think you're uneducated. It's 'you're,' not 'your.'

And yes we are fish.

Maybe you should pay more attention in biology class (and English class).

Anonymous said...

Thank you! I was trying to figure out how to put a cladogram together for biology, your post helped a ton!

canvas art prints said...

Everybody loves a diagram, especially a ven diagram!

grogmarsh said...

there is some proof we come from fish but only solid evidence is that we come from basic bacterium so dont go making a solid statement of "yes, we are fishes"
so unless you can put a fish in a specific set up conditions and get it to evolve as a human being or even resmeble one then we realy do not know we come from fishes.

Alexander M. said...

Well, grogmarsh does have a good point(Even if she/he has a few grammatical errors in her/his comment here and there).

Alexander M. said...

P.s., please don't comment on another's use of the apostrophe if you're not going to use it correctly either. It's not "'you're,'" as you have said, if you were going to use the apostrophes, the comma and you're in that situation, the apostrophe after you're would precede the comma. For all I know, I probably have many errors in this comment.

Anonymous said...

By the way, she/he(Anonymous flamer up there) probably can not be referred to as "uneducated", if he/she were he probably would not have been able to understand anything that you have said. Sure, there is a bit of misunderstanding involved with both of what you think you know about the subject of human classification, but it's okay-it happens; to most humans. If anything, you both are uneducated,but then again, so am I. Who isn't? Who is? I think it's a matter of perspective really.

Alexander M. said...

Oh, and that was my comment up there by Anonymous, I forgot to input my name. My goodness, I've wasted my time, but I felt like saying something so that's that!





Alexander M. said...

Oh and I meant undereducated, geez.

Shalin Siriwaradhana said...

If there's more than 3 sets, is it called as Euler diagram or is there a difference?

Regards,

Shalin @ creately