Skill:
• Construction of dichotomous keys for use in identifying specimens
A dichotomous key is a method of identification whereby groups of organisms are divided into two categories repeatedly
- With each sequential division, more information is revealed about the specific features of a particular organism
- When the organism no longer shares its totality of selected characteristics with any organism, it has been identified
When using a dichotomous key to identify specimens it is preferable to use immutable features (i.e. features that do not change)
- Size, colouration and behavioural patterns may all vary amongst individuals and across lifetimes
- Physical structures (e.g number of limbs) and biological processes (e.g. reproduction methods) make for better characteristics
Dichotomous keys are usually represented in one of two ways:
- As a branching flowchart (diagrammatic representation)
- As a series of paired statements laid out in a numbered sequence (descriptive representation)
Below are some examples of dichotomous keys represented as both diagrams and descriptions (click on image to swap):
Dichotomous Key: Plant Phyla
Dichotomous Key: Invertebrate Phyla
Dichotomous Key: Vertebrate Classes
