Dichotomous Keys

A dichotomous key - method for determining the identity of something by going through a series of choices which leads 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.

It's like playing 20 questions Each alternative leads to another question until the item is identified. It's like playing 20 questions or Guess Who.

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 "needlelike”, 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.

10 Common Mammals of Georgia Example: Page 226 in the Holt Book Dichotomous Key to 10 Common Mammals of Georgia

Lets classify a Cereal !

Use a dichotomous key to identify this cereal.

Is it rice? If yes If no Rice Krispies Go to 2 2. Is it flakes? Go to 3 Cheerios 3. Does it have fruit? Go to 5 Go to 4 4. Does it have sugar? Frosted Flakes Corn Flakes 5. Does it have berries? Special K with Berries Go to 6 6. Does it have raisins? Raisin Bran Granola Flakes with Bananas

rice yes Rice Krispies Frosted Flakes no yes no yes flakes fruit sugar no yes no Kellogg's Corn Flakes Cheerios yes berries Special K with Berries no yes raisins Raisin Bran no Granola Flakes with Bananas

Raisin Bran

Make your own dichotomous key. Get a topic from your teacher You must have a minimum of 6 steps.