The Dichotomous Key: A Classifying Tool

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  • 0:02 Dichotomous Keys
  • 0:30 Using a Dichotomous Key
  • 2:12 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Sometimes, the best way to identify an object is to take a step-by-step approach. Dichotomous keys are perfect for this, helping us classify unknown objects through a series of questions and answers that lead us down the correct path.

Dichotomous Keys

The other day I was walking through the park and I saw a really interesting looking bird. I had no idea what it was, so I needed to go look it up. I could have gone online and tried to describe that bird in a search engine, but instead I chose to use a dichotomous key. These are helpful tools that allow us to identify and classify all sorts of things in the natural world, like birds, fish, trees, insects, flowers, rocks, you name it!

Using a Dichotomous Key

Dichotomous keys are pretty straightforward, and they get their name from the way that you use them. Dichotomous means 'two branches', which is very appropriate because as you go through the key you'll be given two choices at each step. How you proceed depends on how you answer each question, either yes or no. This is similar to how you would work through a flow chart. As you go through each step, you are led to the next choice that is most appropriate based on not only that answer, but also the ones before it.

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