30 minutes

Students will use a simple dichotomous key to identify various species of fish.


Background information about biological classification can be found in the Fact Sheet: Classification.

This lesson is an introduction on using a dichotomous key and assumes students have some basic knowledge of features of fish.

The Lesson: Lolly bags provides a broad overview on what a dichotomous key is and may precede this lesson.

Students will also require a copy of Student Resource Sheets: Fish Dichotomous Key (either individual or in pairs) and Creature Feature (in pairs or small groups). Each student will also require a copy of Student Worksheet: What’s this fish? for your chosen area. You may also like to provide students with a copy of the Poster: Bony Fish – external anatomy.

The Lesson: Fishy Features is an extension of this lesson, where students will construct their own dichotomous key for a given number of species.

Western Australian curriculum

Science Science understanding Biological sciences ACSSU043
Science Science understanding Biological sciences ACSSU111
Science Science inquiry skills Processing and analysing data and information ACSIS129


  1. Recall any prior learning about dichotomous keys – what is their purpose, how do you use them and what types of questions work in a dichotomous key?
  2. Provide students with:

Using the information provided on the Student Resource Sheets: Creature Feature, students will use the dichotomous key to identify the species they have on their worksheets.

  1. Allow students time to complete the activity and then engage them in a discussion about the species they identified and any discrepancies between student identification.


Student worksheets

What’s this fish? North

What’s this fish? Gascoyne

What’s this fish? West

What’s this fish? South

What’s this fish? Indian Ocean Territories


Student resource sheets

Creature Feature

Fish Dichotomous Key


fish anatomy, features, classification, adaptations