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Archive - May 2022

What is Taxonomy?
Taxonomy is the science or technique of classification.

In biology, it is the science concerned with the description, identification, naming and classification of organisms.

The work of classifying organisms is done by scientists called taxonomists. Taxonomists separate types of organisms into a ranking system of more and more specific groupings.

Classification groupings can be confusing, so we are going to start with the seven main categories: kingdom, phylum, class, order, family, genus and species.

The ranking system allows taxonomists to group organisms based on their characteristics and evolutionary relationships. For instance, organisms in a single “order” are more closely related to each other than to organisms in any other “order.” Within an order there will be one or more “family” groups. The organisms in a single “family” are more closely related to each other than to organisms in any other “family.” The number of types of organisms in each category gets smaller as you progress from kingdom through species. The genus and species categories together provide the scientific name of a single type of organism.

Figuring out how an organism should be classified is not easy. Scientists look for structural and genetic similarities among organisms that they classify together but differences and similarities among living things are not always clear-cut. Taxonomists sometimes disagree about the classification of types of organisms. As new information becomes available, they often revise where an organism is placed within the classification system.

​A phylum is next in the taxonomic hierarchy, coming after kingdom and before class. Organisms classified into a phylum have more characteristics in common than they do with the remainder of the species in the same kingdom.

We are going to use a single species to illustrate the taxonomic process. We will start in Kingdom Animalia, the animals.

Not all scientists agree with the following classification scheme, and it is subject to change upon receipt of new information. However, we are going to use it to illustrate the process.

The Kingdom Animalia contains 35 phyla in the world. In Illinois, 17 of these phyla are represented.

We’ll look at four phyla in the Kingdom Animalia and discuss how their members are similar enough to be included in the same phylum.

Phylum: Chordata
The Phylum Chordata contains the vertebrate animals. Mammals, birds, reptiles, amphibians and fishes are included in this phylum. These animals have a notochord at some point in their development. They have a tubular nerve cord along the back. Gill slits and a tail are present at some point in their life cycle. They have an internal skeleton.

Phylum: Arthropoda
The Phylum Arthropoda contains the arthropods. Arthropods have bilateral symmetry and a segmented body. An exoskeleton composed mainly of chitin makes up the body covering. Compound and simple eyes are present. They have an open circulatory system. They have jointed appendages. Insects, spiders, crustaceans, centipedes, millipedes and ticks are some of the species in this phylum.

Phylum: Mollusca
Members of the Phylum Mollusca are soft-bodied animals that usually secrete a shell. They are bilaterally symmetrical. The body is covered by a mantle. Examples are snails, slugs and mollusks.

Phylum: Annelida
The Phylum Annelida contains the segmented worms. Earthworms, leeches and many marine worms are part of this phylum. They have a definite body cavity, and most have a circulatory system. Some have bristlelike hairs. They have a mouth, intestine and anus.

The 17 phyla members in Kingdom Animalia in Illinois.