What Is the Dichotomous Key of a Tree?
A dichotomous key is a series of choices that lead to the identification of an object or person. With respect to trees, a dichotomous key helps narrow down what is known about the tree until the observer can positively identify it. Dichotomous keys are also called taxonomic keys. Does this Spark an idea?
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Choices
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Dichotomous means "divided into two parts." Each step in the key offers two choices. When the observer chooses one of them, he is either presented with another step involving two more choices or he arrives at the name of the object.
Characteristics
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Typically, the choices involve observable, physical characteristics of the item being identified. For example, a tree dichotomous key might ask whether the leaves are thin needles or broad in shape. Based on the answer, the next question may pertain to the shape of cones or whether twigs are set alternate to one another or opposite each other. The answer to those questions takes the observer further along a path toward naming the type of tree she observed.
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Organized Data
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Essential to a dichotomous key is a broad, organized set of data that allows comparison of each set of choices against the information contained in the database. Websites are one place to find these data tables. The data are arranged to present the next set of choices when making decisions at each step. Reliable data make the decision tree possible. Without it, a dichotomous key would not be able to exist.
Long or Short
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Depending on what needs identifying and the physical characteristics necessary for the identification, a dichotomous key could be a long exercise. Tree identification is one process that could become lengthy if you are starting with a single leaf. The leaf may be broad or narrow, smooth or jagged edged, a deep shade of green or a light one. After narrowing the selection for leaves, the same process must be used for twigs, branches, bark, height and other factors. By comparison, the process to identify coins would be short -- copper or silver color, grooved edge or smooth, then a couple of design choices for the front or back of the coin.
Other Uses
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Virtually any observable traits in nature can be compared against the proper data table. Dichotomous keys are used to identify wildflowers, rocks, insects, fish and mammals. Once an organized set of data is available, a dichotomous key can be used to identify other objects as well, such as coins, cars, airplanes, even people. The search for clues is similar to a scavenger hunt, in which the information necessary to proceed is found in the previous step.
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References
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