In the old days we learned that all living things were either plants or animals. Many books nowadays teach that five or six kinds of living things, or kingdoms, exist. Below is one of several representations:

If we go along with the above six-kingdom idea (A more updated version is described on our Tree of Life Page) we can say that each living thing is a member of one of those five kingdoms. What's interesting for us right now is that we can further say that each kingdom is then subdivided into yet smaller groupings. And then those categories are yet further subdivided. And then those are subdivided, and then everything is subdivided again and again... Here we're talking about the system known as classification, a very important topic if you want to learn more about Earth's living things..

In the biological classification system, each level of subdivision has its own name. Here are the names for those levels:

Specialists refer to yet other subdivisions not shown, such as subfamilies, superorders, subspecies and varieties, but the above seven subdivisions are enough to make us happy here.

HOW CLASSIFICATION "WORKS"

To give you a feeling for how these groupings "work," here's a simplified analysis of how they apply to the animal called the human being:

kingdom:  animal
   phylum:  chordate (animals with backbones)
      class:  mammal (with hair, female makes milk)
         order:  primate (apes and monkeys)
            family:  mankind, (with extinct Neanderthals, etc.)
               genus:  Homo
                  species:  sapiens

You see, at every step down the classification ladder, the thing that we are is narrowed down. At first we're just animals. Then the phylum grouping separates us from all animals without backbones, such as sponges, insects, and worms. On down the ladder we go until we land at the species, and at that point we know that we're just talking about one kind of animal, and that animal is us.

Now let's do the same thing with House Sparrows:

kingdom:  animal
   phylum: chordate (animals with backbones)
      class:  bird (egg-layers with feathers)
         order:  passerine (songbirds)
            family:  thick-beaked birds such as finches
               genus:  Passer
                  species:  domesticus

By comparing the two breakdowns, we can see that humans and birds are alike down to class level. We are both animals with backbones, but we humans sure don't belong to the animal class that lays eggs and has feathers.

THE SCIENTIFIC NAME

OK: Here comes something important: Notice that the House Sparrow's last two pigeon-hole names, Passer and domesticus, also happen to be the House Sparrow's scientific name, Passer domesticus. It's like that with all living things. Referring back to our category breakdown for humans, you can confirm that Homo sapiens is the human animal's scientific name.

To get a better feeling for scientific names, there's a great place on the Web sponsored by the US Natural Resources Conservation Service, where you can enter a plant's name, either scientific or common, and see its entire "classification report." To try this out, click here, then type in a plant name in the window. If you need a name, how about "Common Blue Violet?" You should get a page that includes a picture, the plant's distribution, it's entire classification, and more!

So, now it's clear that plant and animal names and plant and animal classification elegantly blend into one another.

BRANCHING AND REBRANCHING

The classification system also reflects the manner by which the various groups and species of organisms arose during the course of evolution by branching off  ancestral species. If we're talking about birds called shrikes and we say that the whole genus has hooked bills, we're implying something profound. We're suggesting that at a certain point in bird evolution a species arose with a hooked bill and other characteristics today associated with shrikes, and this species became the ancestor of all the many shrikes that exist today, the proto-shrike, the first of its genus.

Once you learn the classification of many organisms you'll see that all the subdivisions actually manifest themselves as branches arising from larger branches. This gives rise to the concept of The Tree of Life described on our Tree of Life Page.

SPEAKING THE LANGUAGE OF CLASSIFICATION

To cement in our minds the above concepts, let's practice talking about them. For instance, we can say that the above breakdown shows that all birds belong to the same class. By the same token, all mammals, from mice to humans, belong to the same class. Among plants, all flowering plants comprise the angiosperm class, and all conifers, such as pines and spruces, comprise the conifer class. In the bird world, there are only around thirty orders and one order holds the woodpeckers, another the penguins, and another all the passerines, or perching birds. In the plant world, only specialists deal with orders. Much more important are plant families, such as the Oak Family, the Grass Family, and the Sunflower, or Composite, Family.

Specialists seldom speak of "the Shrew Family" or "the moss division of plants." They use technical, Latinized words. The Shrew Family is the Soricidae, while the moss division of plants is known as the Bryophyta. Since we're beginners, however, we don't really need to wrestle with these terms.

By the way, the science dealing with scientific names is called taxonomy.

BOOKS ON TAXONOMY & CLASSIFICATION: