Keys (Practical)

This lesson covers:

  1. How keys can be used to identify species 
  2. What a 'dichotomous key' is

Keys


In biology, 'keys' are a method of identification whereby groups of organisms are divided into smaller and smaller groups, based on their shared features. With enough divisions, it's possible to identify a type of organism based on its features.

For example, in the key below we can distinguish between all the different types of vertebrates by asking ourselves whether the organism we're looking at has fur, feathers, dry skin, and finally scales.


Diagram showing a key for identifying vertebrates based on features like fur, feathers, dry skin, and scales.

Dichotomous keys 


Most keys (including the one above), are what we call 'dichotomous keys'. All this means is that we only split each group into two groups each time. The majority of keys are dichotomous, but not all keys are.

If an organism has feathers, what type of organism must it be?


Flowchart showing vertebrate identification key with questions about fur, feathers, dry skin, and scales.
Bird

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If an organism doesn't have dry skin and has scales, what type of organism must it be?


Flowchart illustrating the identification of vertebrates based on characteristics such as fur, feathers, dry skin, and scales.
Fish

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