Teaching dichotomous keys in science lessons can be a fun and engaging way to re-introduce students to the concept of taxonomy and identification. By breaking down the characteristics of different species, students understand the process of identifying unknown animals and plants. They also develop critical thinking skills.
This blog post looks at how to introduce and use dichotomous keys successfully in your science lessons with upper elementary or primary (Key Stage 2) children.
Before you start
Before you start, it’s important that students have been introduced to the concept of classification in science. They should understand that that animals and plants are grouped according to their observable features.
Provide examples of dichotomous keys and discuss how they are structured. Dichotomous keys consist of a series of pairs of statements (couplets) or questions, each of which describes a characteristic of the object or organism being identified. The user must choose which statement in the pair best describes the object or organism. They then follow the corresponding path to the next set of statements until they reach an identification.
Using keys
Introduce a simple dichotomous key for pupils to use. You may find it useful to use familiar examples in the first instance, before moving on to identifying unfamiliar objects/organisms.
Whilst keys are most commonly used in the field of biology for identifying organisms, students can practice the concept of keys with a variety of objects. Check out this free ‘identify the candy’ activity on TechersPayTeachers where students identify the candy types using a key.
Create a key
Give students the opportunity to create a key using a small number of objects or organsims (e.g. 4). Students could create a key with the following examples:
- Classroom stationery
- Lunch box items
- People in the class
- Pictures of animals or plants
Once keys have been created, have students try out each other’s to see how well they work.
Some useful tips
- Encourage students not to rush and to read carefully – one wrong observation can lead to a completely different place in the key.
- Remind students to always return to the start of the key when identifying something new.
- Paired work when using or creating a key can promote good discussion.
- When creating a dichotomous key, encourage students to focus on attributes or characteristics they can observe (and not what they already know about something).
It may take students a bit of practice to master the skill of using dichotomous keys but by providing structured, interactive opportunities to both use and make keys, they’ll soon grasp it.
If you’re looking for some ready-made activities where students can practice using and writing a key, visit my TpT store. I have dichotomous key resources with lots of fun examples including dog breeds, pizzas, leprechauns, monsters and more!
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