Creating a dichotomous key

 

Learning Intention: You will understand the purpose of and how to create and use a dichotomous key.

Success Criteria: You will create a key that identifies lollies from a mixed bag, using questions with only two possible answers.

A dichotomous key is a tool used by scientists (especially taxonomists) to identify and name organisms. It uses a series of ‘yes/no’ questions to classify an organism based on the presence or absence of particular features. The questions need to be objective, not subjective, such as “Does it have limbs?”; “Is it symmetrical?” or “Does it have feathers?”. Subjective questions depend on the perspective of the user, such as “Is it big?”; “Is it light in color?” “Does it have lots of legs?” – they are not good questions, because the answer depends on what you are comparing the organism with.

Your task today is to create a dichotomous key to identify a range of lollies. You could use characteristics such as color, shape, melting point, wrapper or symmetry. Remember, each question must have only two possible answers (yes/no or present/absent).

Creating a Dichotomous Key

lollies2

Learning Intention:
Students will understand how a dichotomous key is used to classify and identify organisms in the living world.
Success Criteria:
Each student will produce a digital or paper-based key that uses objective, yes/no questions to identify lollies from a mixture.
Year 7 students are doing a unit on Classification of Living Organisms and learning how to create a dichotomous key. A dichotmous key is what scientists and taxonomists use to identify living organisms. We used mixed lollies and asked the following yes/no, objective questions:

1. Is it hard?
2. Is it circular in shape?
3. Does it have a hole in the middle?
4. Is it sugar-coated?
5. Does it contain chocolate?

Here is one that Sophie created using Bubbl.us:

lollies_Sophiex450