Linnaeus and the world of taxonomy

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DNA (deoxyribonucleic acid): molecular instructions that guide how all living things develop and function...more

Gene: a region of DNA that instructs the cell on how to build protein(s). As a human, you usually get a set of instructions from your mom and another set from your dad... more

Genetic: having to do with how genes passed down from parent to offspring... more

Trait: a characteristic of an organism that can be the result of genes and/or influenced by the environment. Traits can be physical like hair color or the shape and size of a plant leaf. Traits can also be behaviors such as nest building behavior in birds.

From the time of Aristotle, scientists have been arranging living things in order to study and understand them. The science of classifying living things is called taxonomy.

In a classification, a taxon is a group, and the smallest taxon is the species. Usually, only members of the same species can mate with each other and produce young—or seeds, in the case of plants. There are some exceptions to this rule, but often the young of mixed species cannot reproduce or do not survive well in the wild.

Chihuahua and Great Dane

Chihuahua and Great Dane look different but are still the same species.

Since the time of Linnaeus, scientists have attempted to group organisms into higher taxa, or groups.  More than one genus (genera, plural) is put in the same family.  Similar families are put in the same order.  Related orders are put in the same class, and related classes are put in the same division (plants) or phylum (animals).  A number of divisions make up the plant kingdom, and many phyla make up the animal kingdom.  In addition, modern taxonomy recognizes three more kingdoms:  fungi (molds, mushrooms, and their relatives); microorganisms, such as bacteria; and protists, the one-celled organisms you can find in soil and water.

Some organisms don’t look alike but are still members of the same species.  Canis familiaris, our domesticated dog, can be as small as a Chihuahua or as large as a Great Dane. Human experiments in breeding dogs have given us more than 100 varieties. Dogs are classified as follows:

Kingdom—Animalia (note the Latinized spelling)

Phylum—Chordata (presence of a nerve cord along the back)

Class—Mammalia (presence of hair, milk glands)

Order—Carnivora (meat eaters)

Family—Canidae  (dog family)

Genus, speciesCanis familiaris

Other members of the dog family are the fox, the wolf, Canis lupus, and the coyote, Canis latrans. The wolf and coyote are members of the same genus; foxes belong to different genera.

Until recently, scientists did not have access to genetic information and an understanding of DNA. They had to make guesses about what plants or animals are related to each other and belong together. Sometimes their guesses were incorrect. Today, we have much more information about all living organisms and their relationships, and we can correct some of the mistakes in classification that were made in the past.

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Bibliographic details:

  • Article: Taxonomy
  • Author(s): Ruth Kearns
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: May 22, 2010
  • Date accessed: June 12, 2024
  • Link:

APA Style

Ruth Kearns. (2010, May 22). Taxonomy. ASU - Ask A Biologist. Retrieved June 12, 2024 from

American Psychological Association. For more info, see

Chicago Manual of Style

Ruth Kearns. "Taxonomy". ASU - Ask A Biologist. 22 May, 2010.

MLA 2017 Style

Ruth Kearns. "Taxonomy". ASU - Ask A Biologist. 22 May 2010. ASU - Ask A Biologist, Web. 12 Jun 2024.

Modern Language Association, 7th Ed. For more info, see
Quentin Wheeler looking at a beetle
Taxonomist Quentin Wheeler takes a look at his favorite insect - Eleodes.

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