Dichotomous Key

Dichotomous Key

The identification of biological organisms can be greatly simplified using tools such as dichotomous keys.  A dichotomous key is an organized set of couplets of mutually exclusive characteristics of biological organisms.  You simply compare the characteristics of an unknown organism against an appropriate dichotomous key.  These keys will begin with general characteristics and lead to couplets indicating progressively specific characteristics. If the organism falls into one category, you go to the next indicated couplet.  By following the key and making the correct choices, you should be able to identify your specimen to the indicated taxonomic level.

Sample key to some common beans used in the kitchen:




1a.Bean roundGarbanzo bean
1b.Bean elliptical or oblongGo to 2
2a.Bean whiteWhite northern
2b.Bean has dark pigmentsGo to 3
3a.Bean evenly pigmentedGo to 4
3b.Bean pigmentation mottledPinto bean
4a.Bean blackBlack bean
4b.Bean reddish-brownKidney bean

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