A taxonomic key is a device used by biologists for identifying unknown organisms. Keys are constructed so that the user is presented with a series of choices about the characteristics of the unknown organisms; by making the correct choice at each step of the key, the user is ultimately led to the identity of a specimen.

Keys that are based on successive choices between only two statements are known as dichotomous keys and are the type of key preferred by most biologists. Such keys are constructed using contrasting characteristics to divide the organisms in the key into smaller and smaller groups; each time a choice is made, a number of organisms are eliminated. If sufficient characteristics are contrasted, the number of possibilities for the identity of the unknown organism is eventually reduced to one.

Using a Taxonomic Key

Examining a specimen carefully and noting its characteristics before beginning to key it out are good habits to develop when trying to identify plants. Listed below are some other helpful hints for the successful use of taxonomic keys:

• Read any introductory comments concerning the format of the key, abbreviations, and so forth, before using the key.
• Always read both choices presented at each step of the key.
• Use a glossary to find the definition of any terms you do not understand.
• Use a ruler when measurements are required; do not guess.
• Because living organisms are always somewhat variable, do not make a decision based on a single specimen; instead, arrive at an average by examing several different specimens.

This page last updated: 18 Oct 1999