In section 1, you saw a very simplistic example of a dichotomous key. In this section, you will use a more challenging key.

The following is an example of a dichotomous key for identifying fish that might be found in the Great Barrier Reef.

Interactive exercise. Assistance may be required. Click on each image in the key to see a more detailed picture of each fish.

Video segment. Assistance may be required. Watch the following video to see a teacher go through the key to identify two of the fish pictured.

Source: Dichotomous Keys USE, RTHSBiology, YouTube

Use the key to identify the remaining fish. Follow these guidelines when using a dichotomous key.

  1. Identify the unknown objects one at a time.
  2. Start at step one and progress through the steps, as indicated by the key, until the unknown object has been identified.
  3. Select another unknown object and start back at step one. Never start in the middle of the key.

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Sources used in the interactive images, as they appear: