Taxonomy and scientific names

0:00- [Instructor] Did you know that starfish and jellyfish aren't really fish? That's because they don't share many traits with other fishes, like they don't have a backbone or they don't have gills or fins. In contrast, a clownfish is a fish because it does share a lot of its traits with other fishes.

0:16So, these names, which are called common names, can sometimes be pretty confusing. That's because common names can come from many different sources. They can come from appearances or where they're found or based on their behaviors or the season it's associated with, or sometimes even stories in mythology.

0:34In this particular case, all three are found underwater, so they ended up with the name fish. But they also depend on the language. For example, it's fish in English, but in French, it's poisson. In Spanish, it's pez. So these names are literally all over the place.

0:52So, to avoid confusions, scientists use a universal naming system that gives every species a unique scientific name. Let's explore what that system is. Now, before we do that, a quick recap about taxonomy. Remember that taxonomy is a system that scientists use to group and name organisms using their shared and unique traits.

1:18For example, the three domains. This classification is based on the cell type. And the six kingdoms depend on the cell number and how organisms get energy. By comparing more and more traits, scientists eventually narrow every organism down to its most specific classification, the species.

1:39And species is where things get really interesting because this is where organisms receive their scientific name. Every species on Earth gets a name using a two-part system called binomial nomenclature. In this naming system, the first part of the name is the genus, the broader group that the organism belongs to.

2:02The second part is the specific name, which identifies that particular species. For example, that particular spotted jellyfish we spoke about earlier, its scientific name is Mastigias papua, so this is the broader group, the genus to which this organism belongs to, and this represents the specific species.

2:23And notice that the first letter of the genus is capitalized, but the first letter of the species is small, and the whole thing is written in italics, so these are all wrongly written. This is wrong because the first letter of the genus is not capitalized. This is wrong because the first letter of species is capitalized.

2:40It shouldn't be. And this is wrong because although the capitalization is correct, it's not italicized. The whole thing needs to be written in italics. Okay, but one question I always had was, why use two names? Why can't we just call this species, for example, papua?

2:54I mean, that's the species name, so isn't that enough? Well, no, because species names are often based on things like when an organism is found, its color, or some other characteristic. In this case, papua comes from the region of Papua New Guinea, where this jellyfish is commonly found.

3:10But that means many other organisms found here could also end up with the same species name. For example, there's also the Papurana papua, the Papua frog. So, if I just call them papua, I wouldn't know which organism we're talking about. That's why the genus name is essential.

3:25Together, the genus and the species name create one unique scientific name for every single species. So, coming back, this particular starfish is called Asterias rubens. And the clownfish is scientifically called Amphiprion percula. Yeah, these can be pretty hard to pronounce at times.

3:45But when it comes to humans, the scientific name is much easier to pronounce. We humans are Homo sapiens. The Homo represents the broader group our species belong to, the humans. And the sapiens are talking about us specifically. Wait, are there other types of humans?

4:03Well, not today. They're all extinct. Homo neanderthalensis and Homo erectus are examples of extinct human species. Okay, but the last question we could have is, what if scientists discover a brand-new species tomorrow? How do they actually go about giving them their scientific names?

4:19Well, let's take an example. Scientists recently discovered a brand-new species of fish near the Campeche Bank. It's in the Gulf of Mexico, and so the locals naturally started calling it the Campeche Bank hamlet, simply because that's where it was found, but that's just a common name.

4:35How do we give it a scientific name? Well, to do that, first, we need to classify it. It's a multicellular organism, right? And it moves like an animal and it's heterotrophic, so we can immediately place it in the Animalia kingdom. Next, we identify it has a backbone, so it belongs to the phylum Chordata.

4:56Now, we don't really need to remember phyla or anything else. The point is, we identify various traits, like its skeleton is bony. It has fins. We look at the body shape and other anatomical features, and we keep narrowing it down further and further until we reach the genus.

5:18Here, this organism belongs to Hypoplectrus, a small group of reef fish known as hamlets. And finally, we notice that its color pattern and geographic range don't match any known species. It's only found in the Campeche Bank. That means it's an entirely new species of hamlet, so scientists give it a specific name, espinosai.

5:40It's named after a famous Mexican biologist. So, the full scientific name becomes Hypoplectrus espinosai. And what's really cool is that this species was officially named in 2025. So, look, taxonomy is not something scientists finished hundreds of years ago. It's still happening today.

6:00So, long story short, every species on Earth gets a name using a two-part system called binomial nomenclature. The first part of the name is the genus, the broader group to which the organism belongs to, and its first letter is capitalized. And the second part of the name is the specific name, and the first letter of that is not capitalized.

6:22And the whole thing is always italicized.