Dichotomous Key

As we have already seen in the article about biodiversity, the number of existing species cataloged so far is around 1.8 million.

How to order, organize and classify the study of millions of living species, so different from each other?

A simple and ingenious way is: using dichotomous keys.

  • What is a dichotomous key?

The dichotomous key is a tool that allows us to identify elements, if structured in a taxonomy, primarily living organisms. Technically it represents a simple binary algorithm computing comparable to a search algorithm in a data structure (taxonomy), and the resulting categorization of the desired element. Dichotomy research allows biology to classify organisms by using dichotomy, or division into two groups usually based on a peculiar characteristic present in one and absent in the other.



When asked “is bone-fed?” There are only two possible answers:

  • Yes, it will define the family of vertebrates;
  • No, who will define the family of invertebrates;

A dichotomic key is based on the definitions of morphological, macroscopic or microscopic characters; from it there are two possible solutions, whether or not they have a certain character. Repeating the process, it continues until it reaches the identification of the organism in question.

Their use always consists in taking one and only one of the two (or three) alternatives; you must first read the two statements and opt for one of these. Discarding statement is no longer considered in the development of determination.