Tunicates & Taxonomy

Next month, I will be teaching a class about animal groups, families, & taxonomy. Taxonomy shows us how animals (or other objects) are related to one another in a hierarchical structure. There are 7 major groups which we regularly classify animals into, but there are also a wide variety of sub- or super- categories. The major groups of biological classifications are listed below with two examples written out:


American Crow
American Crow
  American Crow North American Giant Octopus
Kingdom Animalia Animalia
Phylum Chordata Mollusca
Class Aves Cephalodpoda
Order Passeriformes Octopoda
Family Corvidae Octopodidae
Genus Corvus Enteroctopus
Species C. brachyrhynchos E. dofleini

Depending on whom you ask, you may find there are 30-38 phyla, the major categories of animals based on their general body plan and developmental or internal organizations. These phyla can vary from containing only one species (Placazoa) to well over a million (Arthropoda).

Coming from a Zoology background, I found that I really like taxonomy and seeing the order and relationships between animals helps me to make sense of how a rock hyrax and an elephant could possibly be close cousins. They are connected in a group called Afrotheria, a superorder of Eutheria (placental mammals) whose relationships have been shown through molecular & DNA anylases.

Here are their classifications:


Rock Hyrax
Rock Hyrax
  Asian Elephant Rock Hyrax
Kingdom Animalia Animalia
Phylum Chordata Chordata
Class Mammalia Mammalia
Infraclass Eutheria Eutheria
Superorder Afrotheria Afrotheria
Order Proboscidea Hyracoidea
Family Elephantidae Procaviidae
Genus Elephas Procavia
Species E. maximus P. capensis

An article came my way about very unusual sea animals found in Antarctica. When I saw the beautiful picture of the tunicates (also known as sea squirts), I wanted to remind myself what these interesting creatures were and who they were related to in the big tree of life.  Although they may look more like “glass tulips” than an animal, these creatures do eat & grow like other animals.  In fact, tunicates are in the same phylum as ourselves, Chordata.  Tunicates, ourselves, hagfish, fish, and other chordates all go through similiar developmental stages that include a notochord (provides support), pharyngeal gill slits (used in feeding), and a tail (helps with locomotion). 

When born, tunicate larvae are similar to small tadpoles, swimming about until they find a suitable rock to settle down on as an adult, cementing themselves to their new home.  Next, they go through many physical changes before fully becoming an adult.  Some tunicates will continue to stay afloat in the ocean their entire lifespan, going through similar metamorphosis as their sedentary cousins.  Tunicates are filter feeders, with in- and out-current siphons.  Food and water is filtered in through their these siphons, then expelled out along with any waste products. 

Here are a few unusual and interesting facts about tunicates:

  • Tunicates are the only animals capable of producing cellulose – produces cell walls in green plants.
  • Tunicate blood contains a high concentration of the metal, vanadium – a metal used to make Lacrosse shafts and simulated Alexandrite jewelry.
  • Tunicate fossils go back as far as the early Cambrian – about 540 million years ago.
  • Tunicates are said to “eat its own brain” during metamorphosis – the tunicate body digests the cerebrial ganglion – a mass of nerves that have a role similar to a brain.
  • Some Tunicates have recently been descovered as invasive species, sometimes hitching a ride on the hulls of ships from one ocean to another.
  • Tunicates are the vertebrates closest living relative.
  • Tunicates are currently being studied in science for certain chemical compounds useful in fighting cancer.


Royal Blue Tunicate
Royal Blue Tunicate
  Royal Blue Tunicate
Kingdom Animalia
Phylum Chordata
Subphylum Urochordata
Class Ascidiacea
Order Enterogona
Suborder Phlebobranchia
Family Diazonidae
Genus Rhopalaea

I want candy! (boom boom boom ba-dum boom)

Candy can be a useful teaching tool, even if you don’t advocate eating it. It’s well known, comes in lots of varieties, and it’s cheap if you buy it in bulk. It can also be used after its expiration date – great for construction, not consumption. I have used it to illustrate cell and organ structure; architectural design and geometric structures; and, by far my most favorite, dichotomous keys and taxonomy.

Candy Cell Labeled

Test plant cell model

I was first introduced to taxonomy in high school. We had to know the classification of every animal we caught for Marine Biology or dissected in Biology. It wasn’t until college, when we were given the oddest assortment of corks, stoppers, nuts, bolts, nails and screws, that I was introduced to dichotomous keys directly. I am addicted to sorting and organizing, so that assignment was one I thoroughly enjoyed. I had to determine relationships, categorize each “specimen,” name it, and create a key so that anyone could figure out which specimen was which. Loved it!

Years later, in a Texas Master Naturalist training class, an instructor used a simple candy dichotomous key to show us how the key worked before letting us tackle the identification of fish. Have you ever noticed the chin barbels on a croaker? I almost missed them. Dichotomous keys can help scientists to identify field specimen and hopefully new species as well.
The idea to use candy to ease the uninitiated into dichotomous keys was brilliant! So of course I borrowed the idea to use with kids. Now, with kids I kept it simple: “use this key to identify the unknown piece of candy – your ‘specimen.'”

To make sure it worked, I made up names for the candy. Almost everyone knows what a Hershey’s kiss is, but what about Smackus pennsylvius? It’s the name I came up with for the kiss – Hershey’s HQ is in Pennsylvania and in cartoons a kiss comes with a pucker-smack sound, hence Smackus (there are a lot of different Hershey kisses, worth their own genus) and pennsylvius after their origin. You can get a lot more complicated by assigning other species names to each kiss, since they do vary and I assume cannot interbreed. I used the original kiss in the key, so went with the origin for the species name.

Before I get too carried away (and I will) here is a simple key I created for one class. See if you can follow the key below to find the names of Smarties, Jolly Ranchers, Reese’s Peanut Butter Cup, Candy Cane and Mar’s Minis Mix (mixed bag mini Mars brand bars).

Candy samples for dichotomous key

In any dichotomous key, you always start at #1. Like a choose-your-own-adventure story, you are given two paths from which to choose. Each number has 2 choices, or characteristics, that describe the specimen. Each step usually gives you an answer or a direction (go to #3). You may skip a step in a key based on the directions you follow. If your specimen doesn’t fit into either characteristic, go back a step and see if you made the right choice. By observing carefully, you can get the right answers. Of course if your specimen doesn’t fit at all, you may have discovered a new species!

1a. Wrapper is metallic material
1b. Wrapper is non-metallic material
go to #2
go to #3
2a. Shape is circular
2b. Shape is rectangular
Gooberis moosi
Rufusastrum micros
3a. Packaged in groups
3b. Packaged individually
Tarticus owlii
go to #4
4a. Multiple colors present
4b. Multiple colors absent
Noelia crutchii
Bombre merrii

See if you can reason out the names once you have matched them up with their candy. I used my imagination, a good dose of silliness (good for the heart) and some actual Latin roots to come up with these names. The great thing about Latin is you can have a lot of fun trying to pronounce it as well! I’ll give answers if you are interested – please comment.

This is a very basic key; it only lists 5 specimens. which could suggest that there are only 5 species of candy. We know that isn’t the case, but remember that this was for kids and maybe the first time they had tried this.

To actually try and classify (and name) all of the candy you can find in a grocery store gets a lot more complicated. But for someone addicted to classification or candy, it sounds to me like a good time. Happy sorting!

Science and Sorting

There have been whole books written about the history and development of the Periodic Table of the Elements, and how that shaped what we know about chemistry now, how great it is, blah, blah, blah. And the Periodic Table is a great and useful tool, but today I’m sticking to some basic fun stuff, like this crocheted periodic table that Erin introduced me to, or the periodic table TABLE.

All you really need to know (for now) is that the chemical elements are pure substances usually considered the building blocks of all the matter in the universe. Hydrogen, oxygen, carbon, lithium, potassium, bismuth, neon, helium, tungsten, copper, and gold are all elements, along with about a hundred or so others. Tom Lehrer wrote a fantastic and ridiculous song, The Elements, which names them all (or at least all the ones known when he wrote the song).

Most of the time we encounter the elements as compounds (like a water molecule is two hydrogen atoms attached to one oxygen atom) or mixtures (like air) or alloys (a special kind of mixture) like steel (iron and friends) or brass (copper and zinc). 

If you want to get picky, then yes, an atom of an element can be broken down into even smaller and simpler building blocks, but I’m not worrying about that now.

So, returning to just the elements, each element has unique characteristics, just like  peanut butter is different from jelly.  Each element has a certain number of protons (the atomic number), and an atomic mass (essentially how much stuff there is in an average atom of that element), and a number of valence electrons (which determines a lot about how the element reacts). 

Don’t get bogged down in what each of those things means, just remember that different elements have different characteristics, just like some shapes have curves and others have angles, or like some animals have two legs, some four, some more, and some none.

Anyway, the point is that if you have different characteristics, you can do some sorting, and sorted options are easier to deal with than a pile of randomness (I bet you select a sorted pair of matching socks most of the time, and prefer that your oatmeal isn’t stored in the same container with chocolate chips, soy sauce, and croutons in your pantry).

Science LOVES classification and sorting, and there are all sorts of systems and methods to do it. One word for these systems is taxonomy (to be distinguished from taxidermy, though you may certainly classify and sort your stuffed road-kill should you so choose.)  Taxonomy often refers to sorting and classifying living or once living things, but it can also mean classifying rocks, stars, etc., based on their characteristics.

Things to Try:

Periodic Table of Office Supplies?

Instead of sorting elements or classifying animals into classes or species, I sorted some office supplies of the order Paperclippius, more commonly known as paper clips.  Go ahead and try this with your own office supplies, pocket change, or whatever small items are handy.

Here is an assortment of specialty paperclips — how could you sort these?

assorted-paper-clips.jpg

 You might sort by color:

paper-clips-sorted-by-color.jpg

Or by shape:

paper-clips-sorted-by-shape.jpg

And both ways have value.  If we sort by color and shape at the same time, a ‘table’ starts to form:

paper-clip-table-1.jpg

And the next step……

paper-clip-table-2.jpg

And the next step……

paper-clip-table-3.jpg

And then we might complete the table this way:

paper-clip-table-4.jpg

But we could have set up our sorting table like this: 

paper-clip-table-4b.jpg

Or like this:

paper-clip-table-4c.jpg

And those ways are just as good — they all sort by both attributes (shape and color), and we know where each type of clip ‘belongs’ in the table.  If we had everything laid out except the blue triangle clip, you would notice the ‘hole’ and know approximately what that clip should look like. 

The existence of many elements in the periodic table was correctly predicted before those elements were discovered, because of the ‘holes’ left in the early versions of the table. Pretty cool, right?