Science project

Dichotomous Key


Learn how to make a dichotomous key. How can we use a dichotomous key to identify plants or animals?


  • Materials are available at the library, office supply store or from home
  • Posterboard
  • Tree, bird, fungus, amphibian, wildflower, etc. field guides
  • Notebook
  • Camera


  • Study examples of dichotomous keys, like the ones below or others you might find in a field guide. There are a variety of ways you can design a dichotomous key, and they can be used to identify pretty much anything. Figure 1 below is a dichotomous key for types of potato chips, and Figure 2 is one for identifying organisms.
  • Practice making a dichotomous key with everyday items or people. Start with the most obvious features of the item and move to more specific statements. Remember, each statement must have 2 choices. For example you might start by creating a dichotomous key to identify students in your class. Begin with very general statements: Is the student male or female? Does the student have blue eyes or brown eyes? Does the student wear glasses? Etc. You can set up your key as a flow chart, or as a grid.

Here is an example of a partial dichotomous key for identifying classmates:

  • When you feel comfortable reading and creating a dichotomous key try to identify something in nature with a key. With an adult’s permission go outside and find a leaf from a tree you do not know. Use the dichotomous key in the tree identification guide you have to identify it.
  • You will create your own field guide that includes a dichotomous key for your project. Choose which group of organisms you will focus on (birds, trees, wildflowers, insects)
  • Pick 5 species in your group that you can see in the wild in your area.
  • Identify some of the features of the species. For example: if you choose 5 types of tree what are some of the shapes of the leaves? What color is the bark? etc.
  • It may be helpful to take photographs or make careful drawings of the features of your chosen species.
  • Work out the details on scrap paper before you try to draw out your dichotomous key on the poster board.
  • When you think you are finished with your dichotomous key try it out by using it to identify each organism. Does it work?
  • In addition to your key create a page of information about each species you have studied. Use pictures and text just like one of your field guides.
  • When you have finished you will have created your own field guide and dichotomous key for local organisms!
Figure 1
Figure 2


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