Name:                                                                 Block:

Building a Dichotomous Key Lab

A dichotomous key helps to identify unknown organisms by using a system that breaks down the characteristics of a set of organisms into two groups.  This is done repeatedly until only one organism of the group remains and can be identified.  Building a dichotomous key requires specific characteristics to be identified from the collection of organisms in order to identify each.  In this lab you will create a dichotomous key for a group of 12 different individuals.

Part A: Creating a Dichotomous Key

  1. Collect twelve organisms and list below how to classify the specimens, i.e. what characteristics do they have.  List as many characteristics as possible as this will be helpful in creating your key.

  1. In the spaces below, identify the common/real name of a specimen that you will be classifying.  Give each specimen an actual/made-up scientific name.  The new names are those that should be used in your dichotomous key.

Common/Real Name

Actual/Made-Up Scientific Name

  1. Create a matrix table to record the presence or absence of identified structures for each specimen.

  1. Using the created matrix, create a flowchart to divide specimens by features; this should look like a bracket.


  1. Create a dichotomous key using statements in which the answer can be “yes” or “no.”

Steps of Dichotomous Key

Go to Step:

1: A

   B

2: A

   B

3: A

   B

4: A

   B

5: A

   B

6: A

   B

7: A

   B

8: A

   B

9: A

   B

10: A

   B

11: A

   B

12: A

   B

Part B: Using a Dichotomous Key

When directed, trade dichotomous keys with another group.  Use their dichotomous key to identify two specimens, identifying each.

Group Member’s Key Being Used:

Specimen Number

Actual/Made-Up Scientific Name

Common/Real Name

Assess their key on the following conditions:

Condition

Y/N

Ability to identify all 12 objects

Only two choices are given at each step

Steps are clear and easy to follow