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Classification keys

Types of classification keys

Did you know, that scientists estimate that there are 8.7 million animal species in this world, and most of them still are not even discovered! You can read more here

With all the different species in the world, we need a method of identifying them. That’s where classification keys come in. These keys are tools that help us identify an organism based on it’s features and behaviours. 


  1. How to identify organisms based on their characteristics and features
  2. How to create and use a dichotomous key
  3. How to create and use a Tabular key

There are many different types of keys scientists use to classify organisms, but the most common are dichotomous and tabular keys. The video below gives a brief explanation on these types of keys.

Dichotomous keys

Dichotomous keys use a series of questions, in which there are only two answers. They can be presented as a branching tree of questions, as seen below. Scientists use this type of key to make simple ‘yes’ or ‘no’ decisions about the organism. For example, do it have gills? does it have legs? 

Dichotomous trees are good for identifying already discovered species, but they won’t work if you’ve found a new species. 

source: https://www.bbc.co.uk/bitesize/guides/zbrmn39/revision/6


Try this dichotomous chart below. Be careful though, if you guess wrong you might be eaten.

Tabular keys

Unlike dichotomous keys, tabular keys are in a table format. They still operate on a single yes, no response, but rather than following a line, you jump to various rows depending on the answer. For example, if it has fur go to row 3, if it doesn’t have fur go to row 2.


  • Dichotomous and tabular keys rely on ‘yes’, ‘no’ answers to descriptive questions to classify an organism.

  • Dichotomous keys are in a branched tree shape, while tabular are in a table. 

Test your knowledge

Click the ‘question mark’ to test your knowledge with some questions and activities.


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