Dichotomous Keys

• A dichotomous key is an organized set of couples (two statements) that consist of mutually exclusive characteristics.
• Dichotomous keys begin with general characteristics and then proceed to specific.
• Dichotomous keys are used to identify unknown organisms.
• Dichotomous keys use a logical and linear method to identify a thing of interest.
• Any morphological characteristic that can be observed on the organisms or objects may be used in a dichotomous key.
• The characteristics used in a dichotomous key must be variable.
• If all of the organisms have a tail, presence or absence of a tail would not be a good couplet in a dichotomous key.
• If only some of the organisms have a tail, it would be a good couplet in a dichotomous key.
• There are two types of dichotomous keys: bracketed and indented.
• Bracketed keys are used when the first number in the couplet is followed by a period (.) and the second number in the couplet is followed by a prime symbol (’).
• Indented keys are used when the first number in the couplet is followed by a period (.) and the second number in the couplet is followed by a prime symbol (’).
• Dichotomous keys are a logical and linear method used to identify a thing of interest.