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 eight different individuals.

Part A: Creating a Dichotomous Key

1. Collect eight 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.

2. 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.

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

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

• Write the characteristics on a horizontal line
• Use a positive (+) symbol indicates the object has the characteristic
• Use a negative (-) symbol indicates the object lacks the characteristic

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

Part B: Using a Dichotomous Key

When directed, trade with another group.  Leave your candy and dichotomous key (packet) for another student to use.  Select a piece of candy that you would like to eat and use their dichotomous key to identify it.

Individual using the Dichotomous Key:

Assess their key on the following conditions: