Scientist quite like classifying stuff, and literally all living things on the planet are no exception. This is done through taxonomy, which in biology is simply the scientific organisation of all living, and once-living but now extinct, things. Our current system of taxonomy has, with some changes, existed since the 1700s, originating with botanist and zoologist Carl Linnaeus. It wasn’t simply a hobby borne out of his enjoyment of organisation (though if filing cabinets in alphabetical order are your thing, this is the job for you!). There are some really important things we can learn about history and evolution from taxonomy too. This week we will be taking a look at how taxonomy works, how things are classified, and how things are named, which is sometimes conventional and other times less so…
Groups of life
The basics of taxonomy is that life is organised into eight main categories, these being Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species. We will explore these in relation to one species. Let’s take a cat for an example.
Domain- This is the broadest category and has three options- bacteria, archaea and eukaryotes. Bacteria and archaea (sometimes known as prokaryotes) are singles celled micro-organisms and do not have a nucleus in their cell. Eukaryotes are multicellular, and do have a cell nucleus, so are pretty much everything else from human to skunk to sunflower. Cats are eukaryotes.
Kingdom- There are six kingdoms which actually include two of the domains. These are animal, plant, fungi and protista, which all fall under eukaryotes, and then bacteria and archaea. Animal (e.g whale), plant (e.g. potato), and fungi (e.g. shitake mushroom) are pretty self-explanatory. Protists are a bit of a ‘and everything else’ category, so everything with a cell nucleus that isn’t a plant animal or fungi. They are single celled and tiny, including things like amoebas. Cats, unsurprisingly, are animals.
Phylum- After kingdom there starts to be a lot of options for the different categories so I won’t go into them all. Phylum is the next broad class, and for animals includes things like chordata (everything with a spinal cord like humans and eels) and arthopoda (insects and crustaceans with segmented bodies and a chitin exoskeleton), and for plants includes groups like bryophyta (mosses) and pinophyta (conifers) and so on for the other kingdoms. Cats are a member of chordata as they have a spinal cord.
Class- There are 108 different classes within the animal kingdom alone, including things like aves (birds) and reptilia (reptiles). Cats belong to the class mammalia as they produce breast milk, have fur or hair, and have three middle ear bones, unlike birds and reptiles.
Order- Still more precise, within mammalia this includes primates (e.g. chimpanzees and gorillas), cetaceans (whales, dolphins and porpoises) and chiroptera (bats). Cats belong to carnivora (large carnivores/omnivores).
Family- e.g canidae (dogs, wolves and foxes) and ursidae (bears). Cats belong to felidae.
Genus– This often makes up the first part of an organism’s scientific name. Whilst felidae includes everything from tigers to lynx to house cats, the genus felis includes only small and medium sized cats.
Species- This is the most precis classification, and often makes up the second part of an organism’s scientific name. For a domestic cat, this is ‘catus’, so a domestic cat’s scientific name is Felis catus, separating it out from the other felis members like African wildcats (Felis lybica) or European wildcat (Felis silvestris).
There’s also a bunch of sub-s and super-s, like subspecies and superfamilies etc… but let’s not get into that.
Levels of similarity
So what can all this organising tell us? The reason why creatures are organised into these groups of varying similarity is that it is believed they share common ancestors due to their similarities. For example domesticated dogs today come in many different shapes and sizes, but certain aspects of them are similar enough that we know that they share a common ancestor, the wolf.
Over a few hundred years with selective breeding, some of their features have changes from one another like size, colour, fur length and some bodily proportions, but their biology still remains pretty similar. We know they are not closely related to crabs because they have very different features, like they don’t have any exoskeleton, or any traces that they have had one in recent history. Crabs and dogs share a kingdom (animalia), but not a phylum (arthropoda vs chordata) so are not closely related. Cats have a biology that is a lot more similar to dogs, and so they share a domain, kingdom, class and order (mammalia), but separate at the grouping of family (canidae vs. felidae).
Working out these groups, and so how closely related organisms are isn’t a simple task. For example bats and birds both do powered fly, yet birds come from the class aves and bats from mammalia, so are far more closely related to many non-flying species like penguins in aves and horses in mammalia than they are to each other. The methods used to group animals together and to work out their ancestry range from looking at their bones to their behaviour to their DNA, and it isn’t a perfect science. These taxonomic groups, whilst based on similar physical features often, are really there to show how closely related animals are. For example earlier I mentioned one of the features of the grouping mammalia is fur or hair, but the hairless sphinx cat wouldn’t be thrown out of the group as it is known to be a species of Felis catus, the rest of whom belong in that category. That one is obvious, but there are many less obvious relationships, and new discoveries often lead to taxonomic groupings having to be changed.
All of this is based on how organisms have evolved from what is thought to be similar or common ancestors in the form of microorganisms, to the variety of lifeforms that we have today. The branches on the taxonomic tree into different groupings shows where the forms of life started going in different directions from one another, like when one group developed a spinal cord whilst another started to develop an exoskeleton instead, traits which they passed on to their future generations. The processes involved in this and what is means in terms of life and inter-relatedness on earth is a huge topic, complex and often misunderstood. It will take far more than a paragraph to explore here, so may be left for a later plog, but for a little more info on why species may diverge from one another you can look up plog “14: Species, mules and pizzlies”. Anyways, we have had enough of the serious and the organised, now it’s time for some of the crazy and the funny.
Names that are classic
Once we get down to species level, everything has a name. There’s the common name like cat, and then the scientific name (known as binomial nomenclature) like Felis catus. This is often derived from Latin words with some logic to them. For example the polar bear is Ursus maritimus. The first part is usually the genus whilst the second part in this case means ‘relating to the sea’, as polar bears often swim in the sea. So it’s sort of like Latin for sea bear. The brown bear is Ursus arctos, ursus being Latin for bear and arctos being Greek for bear, so it’s a bear bear.
There are certain rules with naming, so the scientific name is written in italics with the first word capitalised and the second word uncapitalised. Also they are words that are regularly derived from Greek or Latin, or have a connection to the name of the organism’s genus name. However, not always… When new species are discovered whether living or fossils of extinct species, the discoverer is often allowed to name them which has led to some creative names.
Names that are stupid (or hilarious!)
In 2011 a new sponge-like species of fungus was discovered in Malaysia, orange in colour and around 10×10 cm in size. What did the eminent scientists name it? Spongiforma squarepantsii after SpongeBob SquarePants.
On a less complementary note, an ancient species of pig-like mammal was discovered in the U.S, and subsequently named Dinohyus hollandi. Dinohyus means terrible pig, whilst hollandi was named after the Director of the Carnegie Institute at the time, William Jacob Holland. Apparently he had a habit of taking undue credit for his staff’s work, forcing them to make him a senior author on all their papers no matter his involvement. I don’t think the naming was a complement… Later the animal was actually discovered to be the same species as another ancient pig-like species called Daeodon shoshonensis, and as that one was named first, that was the name they kept for the two of them.
Continuing with the fossil theme, Samuel Turvey discovered a new species of trilobite in China where the Han dynasty is the largest ethnic group. This fossilised species was also the last member of its family Diplagnostidae. Its name? Han solo. Turvey later admitted this name was more to do with a bet with his friends to name it after a Star Wars character than it was about location and taxonomic loneliness.
Puns have also been included. A biologist names Evenhuis name some new species of flies as Pieza rhea and Pieza pi. Clearly the man likes pizza. Some more flies were named in the 1990s by a Mr Marsh as Heerz lukenatcha and Heerz tooya. Terry Erwin named many members of a genus of beetle called Agra. What species names did he choose? Agra vation, Agra phobia, and Agra cadabra to name but a few.
Finally, we have a dinosaur discovered in Brazil and thought to have lived around 110million years ago. It was actually originally found by a commercial fossil dealer who had modified it to ‘look better’ as some parts were missing. This modification involves attaching some other parts of the skull to the snout using car body filler. When it came into the hand of palaeontologists, who wanted to see it in its original form they had a lot of problems remaining the modifications. Due to this frustration, they decided to name the species Irritator challengeri, the first part because they were irritated, and the second part apparently as a tribute to a character in an Arthur Conan Doyle book who was called Professor Challenger.
Taxonomy shows us that not only is the science of life complex, intricate and occasionally changeable, but also filled with humour, frustration, and random bets between colleagues. Classifying life on earth isn’t just organisation, it allows us to better understand how life is interconnected and related, where things come from, and what can happen if your mistreated staff discover an ancient pig-like fossil!
For more info:
Far more in depth info on taxonomy from Encyclopaedia Britannica: https://www.britannica.com/science/taxonomy/A-classification-of-living-organisms
A great video on taxonomy, probably better than my plog on the subject… *cough* also I picked a cat before I saw that he picked a cat…