Plankton Portal Talk

Linnean classification of organisms

  • jo.irisson by jo.irisson translator, scientist


    This image APK0008gzc prompted a discussion about how to call things using scientific names.

    In biology, we use the Linnaean classification, which is organised in hierarchical levels: Kingdom > Phylum > Class > Order > Family > Genus > Species, with many potential intermediate levels. Each level in tis hierarchy, or tree, has a name and all organisms beneath that level can be called that -- for example, we are Homo sapiens but we also are Mammals (class-level name), or Animals (kingdom-level name). The last level is a bit more complicated. The species name is the genus name compounded with a qualificative name. To continue with the example of humans, we belong to the genus Homo and the species Homo sapiens. Our species name is not sapiens, it is the full Homo sapiens (and should be written in italics, as you can see).

    In the case of APK0008gzc, if the animal is indeed a Phronima, its full classification is:

    • Kingdom: Animalia
    • Phylum: Arthropoda
    • Subphylum: Crustacea
    • Class: Malacostraca
    • Order: Amphipoda
    • Suborder: Hyperiidea
    • Superfamily: Phronimoidea
    • Family: Phronimidae
    • Genus: Phronima

    and we can't really tell the species (actually it is even difficult to be definitive about this being a Phronima). So people mentioned hyperiid, amphipod, phronima as potential names, and the good news is that... everybody is right! It is all of those things. They are not mutually exclusive. On the contrary, they are inclusive: Phronima is one of the genera in the Hyperiidae suborder, which, itself, is one suborder of the Amphipoda order, etc.

    Usually, we want to classify things at the lowest possible level, because this is what brings the most information. If we qualify this as a Phronima, we know that it is a Hyperiidae and an amphipod; if we just say "amphipod" it could be plenty of things other than a Phronima (there are at least 9500 species of amphipods, which fit in probably hundreds of genera).

    This is the kind of things that seems like a given, as a scientist, and we don't realise that we need to explain them. I hope it is a bit clearer now.