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20 Questions
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20 Questions
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Most kids have played "20 Questions", but what they don't realize is that they are really practicing a technique scientists use when they identify plants and other living creatures with a dichotomous key.
Introduction:
Play "20 Questions". Pick something or someone in the classroom the students can see. After finding the correct answer, go back and process the strategy students used to narrow their answer down from everything in the room to the one correct answer. Scientists use this same strategy when they come upon a plant or animal they have never seen before. They might first ask "Is it a plant or an animal?" If it is a plant, the next question might be "Is it a tree (over 20 feet when full grown) or not?" Each time a question is asked and answered, the scientist eliminates more possibilities, gradually coming closer and closer to the correct name for what they have found. In this activity, students will see how they can apply the "20 Questions" concept to a real scientific question.
Learning Leaf and Tree Parts:
Before students can solve the "what is this" question, they need to know a bit of the language scientists use when they identify plants. The on-line key does a very good job of showing students some pictures that help define "opposite" and "alternate" branching, etc. If you wish to prep them a litle more, you could do this matching activity (a pdf matching game) to learn those terms.
Preparation for the Computer Lab Activity - Do one of the following:
If there is an abundance of willow branches you can cut without affecting the population or health of individual trees, you might consider bringing branches (with leaves and buds, or just buds) into the classroom. Keep them in a vase to help them last.
or
If you'd rather not collect branches, you can ask students to make detailed drawings of branches, buds, and/or leaves from the willow or another common tree species. Before you ask students to draw, choose twigs from a tree or two that you already can identify and check to see if that species is possible to key out at the address below.
In the Computer Lab:
Ask students to go online and open their browsers to the EEK Tree Key Start page at
They can also get there from the Wolf Ridge Spring Happenings Pussy Willow page by clicking the "Tree Key" link near the bottom of the page.
To use the key, students click on the link with the drawing and description which best represents their twig or sketch. When they have made their final choice and identified their tree, they can click on a link to a more detatiled description of that species. Ask students to read the description and pick one fact to share at the end of class.
Conclusion:
Scientists use identification keys not just to show off how many plants they can name, but as a "key to knowledge." Once you know the name of something, you can find out what others already know about it. Ask students to share the facts they learned. From here, they could do an internet search for Salix discolor (searching for "pussy willow" can lead to some unfriendly results . . . ) and learn about how to grow pussy willows, get them to flower early, medicinal uses, and more.