22.6: Using a Dichotomous Key

In Appendix A there is a key to common campus trees. Note that this key was written for a campus on the far north coast of California, so the trees in your area may be different. A dichotomous key is a tool people use to determine the identity of different organisms. At each step in the key, you are presented with a pair of options, such as “leaves are blue” and “leaves are some color other than blue”. You choose which of these options matches your specimen, then follow the path to either the next set of questions, or the end result. Here is an example from the key:

6a. Leaves palm-shaped, deeply dissected, and emerging opposite from each other on the branch....

Maple

6b. Leaves are not as above ... 7

If the leaves you were looking at matched the description in 6a, you would determine that your specimen as a maple. If they were not palm-shaped, or in some other way didn’t match the description, you would would choose 6b and proceed to the set of questions labelled 7a and 7b to make your next choice.

Use the attached key to identify trees on campus or samples provided in the lab.

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