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Dichotomous key



A reference tool where a series of choices between alternative characters leads progressively to the identification of the species.


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.

Word origin: Latin dichotomos, Greek dichótomos.

Compare: polytomous key

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Gram Positive Cocci

... Negative (does not break down NO) Catalase: Positive Based on the first dichotomous key we had been using it led us to a bacteria called Gaffkya Tetragena, which I could not find ...

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by lucrezia03
Wed Oct 17, 2012 11:58 pm
Forum: Microbiology
Topic: Gram Positive Cocci
Replies: 2
Views: 5362

How to create a science project about acne?

... it would be really hard to test acne the way you are thinking. When you culture bacteria from skin, you have to use several, let's call them dichotomous keys, to determine what kind of bacteria you are looking at. Gram stain is the first step, but then cell shape, cluster patterns, etc all ...

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by tmbirkhead
Sun Sep 23, 2012 5:25 am
Forum: Human Biology
Topic: How to create a science project about acne?
Replies: 2
Views: 5417

Re: gram negative cocci. please help

Your professor should have given you a dichotomous key or some other type of table(s) to help you identify your bacteria. At the very least I would think ...

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by mamasewbusy
Sun Sep 09, 2012 3:39 pm
Forum: Microbiology
Topic: gram negative cocci. please help
Replies: 8
Views: 10760

narrowed down 1 of my unknowns help with other...

... any given species would be identified in the wild. It is more like a dichotomous key (not really if you look at hemolysis here :) ) carefully crafted to separate the different ...

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by canalon
Tue Apr 24, 2012 10:42 am
Forum: Microbiology
Topic: narrowed down 1 of my unknowns help with other...
Replies: 11
Views: 4400

seeking opinion on an unknown

... biochemical tests for a morphological unknown. I am filling out the dichotomous key and would just like opinions as to if I am on the right track. Thanks! So far, I have: ...

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by sully325
Tue Dec 06, 2011 6:11 pm
Forum: Microbiology
Topic: seeking opinion on an unknown
Replies: 1
Views: 1403
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