Do One Thing

Autumn Term 2009

The Do One thing this term is called Trees. This page takes the topic further, and looks at how you can use trees to teach children about classification and making keys. There are five Pupil Worksheets that you can download to support a sequence of lesson activities on this topic. Download the Pupil Worksheets (pdf, 504kB).

Teaching about classification and making keys can be difficult. But by using material from trees and shrubs, you can teach classification in a structured way which shows progression through this topic. By the end, many of the children should be able to name some of the trees that they see around them. A possible plan for teaching about classification using trees is

1. Using a simple key
2. Describing the leaves
3. Sorting the leaves into groups
4. Making a key

More teaching and learning materials on classification can be found on the KS3 Science Fieldwork site.

1. Using a simple key

It is useful for children to have experience of using keys before they start. Here is a simple yes/no key to 6 different types of sweets.

This is an extract from the Field Studies Council / Forestry Commission Tree Name Trail. It is a key to the main trees and shrubs found in Britain. Children answer questions to follow the trail to the answer.

Find out more about the Tree Name Trail.

2. Describing the leaves

Leaves from nine common types of trees are shown below. There is clear variation in the shape and size of the leaves.

Rowan	Oak	Beech
Birch	Ash	Hazel
Sycamore	Plane	Horse chestnut

How can these different leaf shapes be described? The following features are useful for sorting the leaves into groups:

• structure of the leaf: simple leaves and compound leaves
• veins on the leaf: pinnate leaves and palmate leaves
• the leaf margin: toothed, lobed or entire

Structure of the leaf: simple leaves and compound leaves

• In a simple leaf, the leaf is not divided into leaflets
• In a compound leaf, the leaf is divided into leaflets

How can you tell the difference between a leaf and a leaflet? Look for the postion of the axillary bud. Buds are found on the axils of leaf stalks. Buds are not found on the axils of leaflet stalks.

Sycamore a simple leaf	Oak a simple leaf
Rowan a compound leaf	Horse chestnut a compound leaf

Veins on the leaf: pinnate leaves and palmate leaves

• In a pinnate leaf, there is a main vein in the middle of the leaf with side veins coming off it
• In a palmate leaf, there are several main veins

Oak a pinnate simple leaf	Rowan a pinnate compound leaf
Sycamore a palmate simple leaf	Horse chestnut a palmate compound leaf

Pupil Worksheets 1 and 2 introduce pupils to the terms simple, compound, palmate and pinnate. Download the Pupil Worksheets (pdf, 504kB).

The leaf margin: toothed, lobed or entire

There are three useful terms for describing the leaf margin (the edge of the leaf): toothed, lobed and entire. A leaf margin which is neither toothed nor lobed is entire.

Sycamore - the leaf margin is toothed and lobed	Oak - the leaf margin is lobed but not toothed	Beech - the leaf margin is entire (not toothed, not lobed)

3. Sorting the leaves into groups

Pupil Worksheet 3 supports pupils support leaves into groups. Download the Pupil Worksheets (pdf, 504kB).

Using secateurs, collect leaves from a small number (between 5 and 8) of different trees and shrubs. Ideally these should be in the school grounds or in the close vicinity of the school so that pupils have the opportunity to see the whole trees and shrubs. You will need enough leaves for each of your groups / pairs of pupils to have a set of leaves. Make sure that you have the permission of the landowner before collecting specimens. In late autumn you can collect fallen leaves from under each tree instead. Choose a range of leaves which have obvious differences in shape. See the photographs above (on blue backgrounds) for some ideas.

Divide pupils into small groups and give each group a complete set of the leaves. Ask them to sort (classify) them into 2 sets, each of which has a common characteristic. It is not essential for the sets do not have to be the same size. Next ask them to sort these two sets into 2 further sets and continue to do this until they have separated all the leaves.

4. Making a key

Making a key follows naturally from the previous activity. Pupil Worksheet 4 can be used. Pupils may find this sheet easier to use if it is enlarged to A3 size. Download the Pupil Worksheets (pdf, 504kB).

Pupils write down the characters that they used to sort the leaves in the ‘tree diagram’. Where possible encourage pupils to write down opposite characters rather than just negatives e.g. leaf simple / leaf compound rather than leaf simple / leaf not simple.

Branches can be added and not all the branches need to be used. Explain that this diagram forms a simple identification key.

At the end of the exercise each group can pass their ‘key’ to an adjacent group who try it out. Pupils can use the table in Pupil Worksheet 5 to help support their evaluation of the usefulness of each character. Download the Pupil Worksheets (pdf, 504kB).

When pupils have had an opportunity to test each others’ keys consider the following points with them

1. Which characters do they think are the best ones to use to separate the leaves into groups?

Put a list of the characters used by the groups on the board and discuss:

• which of these characters were easiest to see?
• which characters were the most variable in leaves of the same type? (very variable characters are not reliable for sorting)
• which were the characters easiest to describe or define? Point out that descriptions need to be objective e.g. large/small is not

Colour, shape and size may also be useful, but need to be carefully defined and size ranges given where necessary.

Ask the pupils to think about the advantages / disadvantages of having subsets unequal in size. Generally if the sub-sets are all equal in size the key is shorter – it has fewer steps. Separating all the species off one at a time is not a good idea. It makes the key long and sub-sets with common characteristics are not highlighted. However, a ‘user friendly’ key may use a very distinctive character to separate a small sub-set or even an individual at the beginning of the key.

More information

• SAPS (Science and Plants for Schools) have produced a 40 page booklet for teachers called Grouping and classification. In this booklet, children explore the nature of living things, find ways to group living and non-living things, and understand how we classify living things and why we give them names. Children learn to make simple keys and use them to identify common plants. Grouping and classification can be downloaded for free from the SAPS website.
  
• Field Studies Council produce a wide range of keys to plants and animals, ranging from simple-to-use fold-out charts to minibeasts and plants to more specialised guides.
  
• Materials for teaching the topic Variation and classification can be downloaded for free from KS3 Science Fieldwork. Although aimed at teachers of Year 7, it may be of some use for teachers putting together extension activities for older primary pupils.
• Interested in taking part in a Europe-wide fieldwork survey? Find out more about the BEAGLE project (pdf, 280kB).