What on Earth is Taxonomy?

Welcome to the second Science for Writers post. Last weeks we discussed the Higgs Boson but this week we are going to the other side of the science spectrum and into the realm of biology with a discussion on Taxonomy.

I have put important words in bold. These words are important in biology and I will refer to them throughout the post. It isn't overly important for you to know the exact meaning, so long as you get the gist of what I'm talking about you will be fine following this post.

Writing Links are in italics and these discuss how the science could be used in writing.

A bit of background science

In biology it is important to classify different organisms. This classification is done so that organisms with similar biological characteristics are grouped together which makes researching them and discussing them a whole lot easier.

The system works down to identify species. Before any further discussion can be made we should look at the definition of a species:

A species comprises a a group of individuals that can usually breed to produce fertile offspring.

Fertile offspring means that the offspring can mate to produce more of that species. For example two horses can mate a produce a foal (baby horse) that when mature can mate with other horses to produce further foal. A horse and donkey, however, can mate together to produce a mule. But, a mule is not fertile so is not a species and this also means horses and donkeys are different species.

Writing Link:  Two different species can't mate to produce fertile offspring, but they do produce offspring (such as the mule). If you are writing a Fantasy or Sci-Fi then you might want to think about the potential for two different species to breed together and what being infertile means to the offspring.

Taxonomy

Taxonomy is a method of classifying organisms from very broad groups to specific species.

Taxonomic System
from Wikipedia

We start out by ensuring the thing is living. Non-living things such as rocks, glass and metal are not classified on this scale. Next divides everything into two domains. These are eukaryotes (the organisms' cells have a nucleus) and include humans, and prokaryotes (the organisms' cells don't have a nucleus) which include bacteria.

Then we break down into the kingdoms: Bacteria, Archaea, Protoctista, Plantae, Fungi, Animalia. We will look at these in more detail alter on.

Next are the phylums, of which there are too many to list. Most notable is Chordata of which we belong.

Then there are the classes. You might recognise some, but there are a many I'm not listing. Mammalia, Insecta, Amphibia, etc...

Next up are orders such as Primates, Carnivora, Fabales, etc...

Then it's the family such as Ursidae, Felis, Hominidae, Fabaceae, etc...

Next are the genera (plural for genus) including Homo, Pisim, Escherichia, etc...

Finally you have the species. The naming of species follows a rule known as the Binomial System which assigns species there name based on their genus (capitalised) and the specific name/epithet (not capitalised). An example of a specific epithet is sapiens. Therefore the species name is Homo sapiens.

Writing Link:  The taxonomic system used to classify organisms need not stop on Earth. If you write Sci-fi then you could try coming up with new classifications for your species based on taxonomy.  Does it class as life? Do the cells that make up its body contain genetic information in a nucleus (eukaryote) or freely in the cell (prokaryote)? Do you class it as an animal? Essentially how far does an alien species get on our taxonomic system before new groups have to be created? The majority of names within each taxonomic group come from Latin. If you write Fantasy you could use your own language base to name the sets within each group.

A few Classifications

Let's start off with humans. We are definitely living and our cells have nuclei so we are eukaryotes. Our kingdom is Animlia (we are animals no matter the argument) and as we have a central chord, our phylum is Chordata. As we produce heat internally, have three middle ear bones, mothers have functional mammary glands, our teeth are replaced only once (or not at all) and we have other defining features of the class we are in the class Mammalia. Our order is, of course, Primate as we have a whole list of defining features including five fingers with opposable thumbs, sensitive pads on the end of digits, well developed cerebellum, large brain size (proportionally to the body). Our family is Hominidae and our genus Homo. That leaves our species as Homo sapiens.

Writing Link:  Look at the defining features of the different taxonomic classifications and see if you can create any interesting new species for fantasy and sci-fi works.

Now let's look at another mammal, the lion:

Taxonomy of a lion courtesy of smc.edu

On this diagram there are a few more things we haven't covered yet. I'll briefly go over these. Firstly the arrows show how many species are in each section. There are the most species in the Kingdom as this covers all species that are in that kingdom. For Animalia that includes humans, tigers, lions, frogs, fish, etc... You can imagine it like an upside-down triangle. The point represents one single species and the wide top represents the kingdom. The titles in (brackets) are just sup-classifications biologists use.

Can you see where humans differ from lions? At the order. We are order Primate, lions are order Carnivora. This means humans have a common ancestor somewhere up the line with lions and this species was in the class Mammalia.

Note:  The species name for a lion is actually Felis concolor where concolor is the specific epithet.

Writing Link:  Where do your species have common ancestors? This doesn't mean great-great grandparents, but at what point did a species diversify to the point where it was classified differently meaning one route of evolution led to one species and a different route to another.

Now let's look at the field mushroom:

Taxonomy of Mushroom
courtesy of Wikipedia

As you can see there is no link between us and a mushroom on this taxonomic scale. However, if you extend the scale to include the domains you will see that mushrooms are eukaryotes and so have a common ancestor with us that was also a eukaryote.

The species name is Agaricus campestris. However as Agaricus is hard to remember, spell, and say, biologists, abbreviate it to A. Similarly Homo Sapiens can be written H. Sapiens.

Note:  A common ancestor is at the point where a species splits into a different taxonomic group. This diagram should help. At any point where lines split is where thee common ancestor for the species that follow are. Examples of common ancestry points are shown with circles but not all common ancestry points are indicated.

Common Ancestry courtesy of Scienceblogs.com

And that is about it for taxonomy. If you are interested you can search pretty much any organism on wikipedia and the sidebar will give you the taxonomic classification.

I hope this has been helpful. Please post in the comments your thoughts on the post and any science you'd like explaining in a future Science for Writers post.

Thanks,

Matt B