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Biology LibreTexts

Part 1: A Simple Dichotomous Key

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  • A dichotomous key is a tool used to determine the identity of species that have been previously described. You can think of it as a series of questions in which each question only has two possible answers.

    In the table below, you have been given a list of creatures and their descriptions. The different characteristics, behaviors, and habitats of the creatures can be used in the dichotomous key to differentiate among them.

    Creature Description
    Jackelope Mean-spirited horned jack rabbit
    Chupacabra Reptilian creature covered in scales with spines along the dorsal ridge; likes to eat goats
    Altamaha-ha Water monster with an alligator-like head and long neck; lives in the marshes of Coastal Georgia
    Sasquatch Stinky giant humanoid covered in brown fur; found in the forests of North America
    Yeti Giant mountain humanoid covered in white fur; prefers the snow
    Kraken Giant octopus-like creature; takes down ships in the open ocean
    Nessie Water monster with a snake-like head and long neck; lives in Loch Ness, in the Scottish highlands

    Below, you will find the dichotomous key used to identify a folkloric creature you may come across. On the left is the list of questions and on the right, the same list is represented as a flowchart. Both are useful representations of the same dichotomous key.

    1. Does the creature live on land?Screen Shot 2019-01-01 at 5.29.38 PM.png

    a. Yes: go to question 2

    b. No: go to question 5

    2. Does the creature resemble a human?

    a. Yes: go to question 3

    b. No: go to question 4

    3. Does the creature have brown fur?

    a. Yes: Sasquatch!

    b. No: Yeti!

    4. Does the creature have scales?

    a. Yes: Chupacabra!

    b. No: Jackelope!

    5. Does the creature have tentacles?

    a. Yes: Kraken!

    b. No: go to question 6

    6. Does the creature have a large head, resembling an alligator?

    a. Yes: Altamaha-ha!

    b. No: Nessie!


    Using the dichotomous key, identify the creature at right.    Screen Shot 2019-01-01 at 7.49.37 PM.png

                                                                                                                      Figure \(\PageIndex{1}\) "Patterson–Gimlin film frame 352" byPatterson-Gimlin film. Via Wikipedia