Teacher instructions

Work through this resource material in the following sequence:

20 minutes

Tune in: Why do we Classify Living Things?

20 minutes

Find out: Using a Dichotomous Key

20 minutes

Take action: Creating a dichotomous key

Tune in: Why do we Classify Living Things?

Step 1.

Consider heading outside for this activity.

Ask your students to sit quietly outdoors and observe all the living things around them (excluding other students and teachers!)

Encourage students to observe both the small and large living things around them: get down low and up close to look at the small things; look into the distance and up high to observe the larger living things.

Invite students to share the different living things they see.

Step 2.

Now ask students to share the living things they see in terms of species and their common name. Although students may not know the names of all the living things they see, they should be able to differentiate the main ones - different types of trees, different types of bugs, etc.

Step 3.

Finally, ask students to share the names of some things by their scientific name. Does anyone know any?

Step 4. Discuss:

How do we know a thing is living?

M - Movement - the organism can change its position.
R - Respiration - the organism releases energy from a 'food' source: this requires oxygen.
S - Sensitivity - the organism responds to things.
G - Growth - the organism gets bigger.
R - Reproduction - the organism can make copies of itself.
E - Excretion - the organism gets rid of waste materials.
N - Nutrition - the organism consumes chemical materials as food.
Which of the following is living or not living? Why?
- Cheese
- Log
- Water
- Egg
- Fire
- Banana

Step 5. Explain:

We don’t really know how many living things there are on Earth, although estimates suggest that in terms of mass, there are around 75 billion tonnes of living things. One of the goals of science has been to understand more about these living things, and in particular their relationships between each other and their relationships with people.

The first step in understanding living things is to classify them. Classification means putting things into groups.

Step 6. Discuss:

Why do we classify things? There are generally three reasons why we classify things:

Because it makes it easier to remember organisms
So each organism has a name that is recognised around the world
So scientists in different countries can talk about the same organisms

Find out: Using a Dichotomous Key

Step 1.

We know there is a system of classification that is recognised by scientists around the world (hierarchical system of taxonomy, see our lesson here). When we know the scientific name of the organism we are looking at, it is easy for us to find out how this species fits into the classification system.

However, what happens when we don’t know the name of an organism? How can we find out its name, let alone where how it is classified?

One way to identify an organism is to use a dichotomous key. Dichotomous keys are useful tools that help us organise things into identifiable groups by classifying things according to whether a particular characteristic is present or absent.

Ask students to look at the two examples of dichotomous keys on the Student Worksheet:

Step 2.

Now invite students to work in pairs and use the Schoolyard dichotomous key to identify something they can see around them.

Once complete, ask students to share their answers, talking about their experience of using the dichotomous key (questions also available on the Student Worksheet):

What did you like about this key?
What didn’t you like?
How do you think the key could be improved?

Step 3.

Students select an invertebrate, either one they can see or one from their memory.

Students identify the invertebrate using the CSIRO Key to Invertebrates.

Take action: Creating a dichotomous key

Step 1.

Display the Images of Plants. These include:

Some roses
Some gum trees
Some grass
An oak tree
Some daisy
Some daisies
A cactus

Explain to students that these are all plants, but they're not the same plant (obviously). We need a way of differentiating between them. A dichotomous key would be handy.

Independently, students create a dichotomous key for these plants. Students will need to create these keys in their workbooks.

Students can include more types of plants if they wish, such as vegetables, non-flowering bushes, or weeds.

Step 2.

Once complete, ask students to swap their keys with another student and test the keys. Each student will need to assess the keys and make recommendations for improvement where necessary.

Reflection

What was challenging about creating this key?
What was a recommendation made that you didn't think of in your original key? Why did you not include it?

Outdoor Learning - Classifying Living Things Using Dichotomous Keys

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