Halim found an animal in a stream deep in a forest.

Which of the following characteristics should she use to identify it as amphibian, fish or reptile?

(1) presence of gills

(2) type of body covering

(3) method of reproduction

(4) whether it can live both on land and in water

Below is how most students would have evaluated the four options.

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Based on the flow chart above, we will not be able to arrive at an answer as the maximum number of groups we can split the animals into for each condition is two.

Below is the schema students need to use to answer this question:

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So, students need to dig a little deeper and realise that they will somehow need to further differentiate the classes of animals for one of the conditions. The only options that allow for this possibility are ‘type of body covering’ and ‘method of reproduction’.

This means students should ask themselves if reptiles and fish have different types of scales, or if reptiles, amphibians and fish lay different types of eggs (other interpretations of ‘method of reproduction’ such as method of fertilisation need not be considered because they are not covered in Primary School Science syllabus).

However, a quick survey of our students shows that distinguishing between different types of scales and different types of eggs is not something that is taught in every school or enrichment centre.

So, here’s what students actually need to know in order to answer the question.

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Moral of the story: it’s always good to know a little more.

The Primary School Science syllabus is more concept rather than content-heavy, so teachers and parents should look out for opportunities to broaden students’ scientific horizons through interesting and engaging extension activities. This form of extension will not only deepen a student’s understanding of a scientific principle/concept, it will enrich their knowledge of the world around them.

If that sounds like too much work, well, you can always outsource the important job to Joyous Learning. Click here to register online for a trial class!


Options (1) and (4) can be eliminated using logic alone without the need for scientific knowledge. There are three categories of animals to be distinguished from each other, namely amphibian, fish and reptile. However, since option (1) and (4) are conditions that yield only two possibilities – ‘yes’ or ‘no’ – they can be eliminated straightaway.

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