1. Dichotomous Keys
SBI3U

2. Dichotomous Key
A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.

3. Dichotomous Keys Dichotomous means "divided in two parts".1 2 3 4 5 6
Dichotomous means "divided in two parts".
Each step has two choices; what you choose leads you to another question until the item is identified.
Based on physical characteristics.

4. Dichotomous key
Example of a dichotomous key…

5. Dichotomous key
the dichotomous key can also be expressed in a diagrammatic form

6. Dichotomous Key Activity
Obtain 6 different shells and a bag.
Name your shells as a unique binomial species.
Create a dichotomous key that could be used to identify each species of shells.
Exchange your dichotomous key with another group in the class and use each other’s key to properly identify the species according to the other group’s assigned names.
Fill in the assessment sheet for the group whose key you are using and return it to them when finished.

7. GROUP TASK Each group gets ONE bag Place 6 shells in the bag.
Make a Dichotomous key for ALL the items in the bag.
Follow procedures on the
handout. 1 2 3 4 5 6

8. PROCEDURES First make and answer key.
Write the names of your partners and bag # on your ANSWER key.
Assign a number to each object and make up a new name “scientific name” for each object.
Example: # Mollusca minuta (small shell)
May want to trace an outline of the object
Make a dichotomous key for all objects in your bag.

9. Assessing the Effectiveness of Keys
Switch bags and keys with another group.
Use their key to identify their items.
Write the scientific name next to the object name.
Give them a level grade on their descriptions and accuracy of the items.