Dichotomous Key

October 3—Explain how to correctly use a dichotomous key.  What is its purpose?  How did you go about creating your own algae dichotomous key in class?  What problems did you encounter, and how did you solve them?

 A dichotomous key is usually a written device constructed from a series of highly organized statements arranged into couplets. A couplet consists of (typically) two descriptions which should represent mutually exclusive choices (often it is a particular combination of characteristics that determines the difference). Both choices are read and compared with the specimen to be identified. Once a decision is made, that selection directs you to another couplet (either the next in order or one further on in the key), and this process is repeated until a conclusion (successful identification) is reached.


The purpose of a dichotomous key is to take an organism and make note of its features and then look at a dichotomous key to identify what species it is based on its features. 

For creating our our dichotomous key in class, we took algaes and grouped them based on smells, colors, shapes, cell numbers, things like that.

The only problem we encountered was when there was a similar algae that had the same quality in both, we had to change it and make the feature more vague instead of so descriptive.