1. A Key to Identification:
Dichotomous Keys

2. Dichotomous Keys
This is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.
Keys consist of a series of choices that lead the user to the correct name of a given item.
Dichotomous actually means “divided into two parts.”
Therefore, dichotomous keys always give two choices in each step.

3. Example selection from a dichotomous key
a. wings covered by exoskeleton….go to step 2
b. wings not covered by exoskeleton…go to step 3
2. a. body has a round shape…lady bug
b. body has an elongated shape…grasshopper
3. a. wings point out from the side of the body..dragonfly
b. wings point to the posterior of the body…housefly

4. Purpose
To learn skills in the areas of observing, comparing, communicating, ordering, and categorizing.

5. Steps to making dichotomous keys
Use constant characteristics that are observable.
This means that when you observe that object at a later time, you will be able to use the same characteristics to describe it.

6. Steps to making dichotomous keys
Use measurements rather than terms such as “large” and “small.”

7. Steps to making dichotomous keys
Make sure that there is no doubt to the way you are characterizing things.
Example: Don’t say that something is red if it may be considered pink by other people.

8. Steps to using dichotomous keys
Always start at the top (step 1) of the key.
Always read both descriptions before deciding where to go next. Even if the first choice seems to be the logical one at first.
Be sure you understand the meaning of the terms involved. DO NOT GUESS.