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Definition

Dichotomous Key: is 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. 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.

"Dichotomous" comes from a Greek word that means cut into two parts. Therefore, dichotomous keys always give two choices in each step.

Hawaiian Translation: 'Āmama Koho


Example

taxonomic Key

Aristotle was one of the great thinkers of his time. One of his achievements was to outline a scientific classification of animals.   He observed many animals to find features by which to classify them.  
This figure is a dichotomous key which shows animals classified by the characteristics determined by Aristotle.


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