Constructing & Using a Key
- Keys are used to identify organisms based on a series of questions about their features
- Dichotomous means ‘branching into two’ and it leads the user through to the name of the organism by giving two descriptions at a time and asking them to choose
- Each choice leads the user onto another two descriptions
- In order to successfully navigate a key, you need to pick a single organism to start with and follow the statements from the beginning until you find the name
- You then pick another organism and start at the beginning of the key again, repeating until all organisms are named
Example of a dichotomous key #1
Example of a dichotomous key #2
Exam Tip
Simple dichotomous keys almost always come up in the multiple choice paper, so make sure you can use one.
Very occasionally they show up in the theory paper, and when they do you almost always have to use one instead of constructing one, so focus on this rather than spending hours learning to construct them yourself!
