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HomeHomeFAQsFAQsGeneral FAQsGeneral FAQsWhat is a dichotomous key?What is a dichotomous key?
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3/19/2008 4:26 PM
 

Dichotomous keys are the most common keys encountered. They may be laid out in various ways, but usually form a series of numbered questions arranged in "couplets" as shown below

1. Bark on trunk smooth.................................. 2
Bark on trunk rough.................................... 3

2. Bark mostly white....................................... 4
Bark other colours....................................... 7

Each time a question is answered, the user is directed to the number of a new question-couplet and the key continues to do this until instead of a number, the name of the species (or other taxon) is given. This type of key is called a "dichotomous" key because the meaning of the word is "two branching". The structure of the key is such that each question is actually like a tree branch that has two smaller branches proceeding from it as demonstrated on the next page.

Despite their wide use, dichotomous keys suffer from one very bad problem – you have no choice about the order in which characters are presented. For instance, suppose you are trying to identify a plant and the next couplet is about the colour of the flowers, but the material you have only has fruits. You can go no further with any confidence. Lucid Phoenix can help overcome this problem by allowing you to skip couple questions and help manage your selected path through the key.

 
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HomeHomeFAQsFAQsGeneral FAQsGeneral FAQsWhat is a dichotomous key?What is a dichotomous key?


  
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