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EnchantedLearning.com Make a Dichotomous Key: Classroom Activity

Plant Dictionary

A dichotomous key is a series of questions which leads to the identification of an item.

A dichotomous key is a method for determining the identity of something (like the name of a butterfly, a plant, a lichen, or a rock) by going through a series of choices that leads the user to the correct name of the item. Dichotomous means "divided in two parts".

At each step of the process of using the key, the user is given two choices; each alternative leads to another question until the item is identified. (It's like playing 20 questions.)

For example, a question in a dichotomous key for trees might be something like, "Are the leaves flat or needle-like?" If the answer was "needle-like," then the next question might be something like, "Are the needles in a bunch or are they spread along the branch?" Eventually, when enough questions have been answered, the identity of the tree is revealed.

Classroom Activity:

As a simple example, you can construct a dichotomous key to identify people (or another group of items) in a classroom, using questions based on gender, hair length/color, glasses (or not), clothing color, etc. Question 1: Is the person male or female? Question 2: Does the person wear glasses or not? Question 3: Is the person wearing blue jeans or not? etc. The end of each branch of the key should be a person's name. A dichotomous key will have enough questions to identify each member of the group. To test it, you can identify each person in the group by going through the key and seeing if the right name comes up.

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