How to make a Dichotomous Key

Wednesday, April 28, 2021

A dichotomous key is a tool that allows the user to determine the identity of items. This can include trees, animals, rocks, and even monsters. The term Dichotomous means "divided into two parts" therefore each question on a dichotomous key is divided into two parts.

In this video, I will show you how to create a simple dichotomous key but this works for more complex keys as well.

Let’s create a dichotomous key for these 7 monsters.

How to build a dichotomous key

Step 1 involves figuring out how many pairs of questions you will need. I have 7 monsters so I will need 6 pairs of questions.

Now let’s divide the monsters into two main groups.

I can do this with the question Monster has legs and the monster does not have legs.

How to build a dichotomous key

When you divide the monsters you have four monsters with legs and 3 monsters without legs.

Because you have 4 monsters with legs you will need 4 questions to divide this group,

1a will be monster has legs and will go to 2

Question 1b will be monster does not have legs and will go to 5 because I have four monsters with legs.

Now let’s go to question 2

We have 4 monsters and we need to start sorting them so let’s go with the number of eyes

2a Monster has 5 eyes ……  Multieye

2b Monster does not have five eyes.

How to build a dichotomous key
Now let’s divide these,

How to build a dichotomous key

We can go with 

3a monster has horns   will be Bullhorn

3b Monster does not have horns go to 4

Now I will not use a yes-no question but go with characteristics

4a Monster is pink ….. Is bigfoot

4b Monster is turquoise  …. Will be Smiley

Now we move to the monster’s without legs.

How to build a dichotomous key

5a Monster has one eye .. will be cyclops

5b Monster does not have one eye….. Go to 6

Again the last question will not be a yes-no question

6a Monster has more than 6 eyes ….. Is eye pop

6b Monster has two eyes …. Is   Winger

How to build a dichotomous key

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