Teacher Preparation

Overarching learning goal: By participating in this activity students investigate the species in a confined ecosystem, collect mathematical data about species diversity and choose appropriate scientific equipment to complete the investigation.

Teacher content information: A compost bin is an enclosed ecosystem. After some time the compost bin will host a range of common soil and leaf litter creatures, along with animals that are attracted to rotting fruit and other vegetable material, fungus and moulds.

Species biodiversity can be studied mathematically. In a study on compost bins, a comparison could be made of species diversity over time, between compost bins content and seasonal change.

Safety - Students should not work with dry compost material. Exposed dry composed material should never be kept indoors. Dry compost material, particularly commercial products can produce dangerous airborne bacteria.

This is a student-led activity. Students can work independently or in pairs or groups.

Student and classroom organisation

Step 1.

Ask students to view the Student Worksheet so they can design their own investigation.

The teacher will need approximately one bucket of fresh compost. You will find most of the organisms in the very top layer of the green waste where it is starting to decompose.

The student challenge is to:

1. Identify how many species they can observe in a specimen from a compost bin.

2. Sort the species into rough categories that include type of organism and size. Type of organisms include:

Insects and insect like creature with six legs
Insects with no legs – maggots and grubs
Spiders and mites with eight legs
Slaters and pill bugs
Millipedes and centipedes
Snails and slugs
Lizards
Fungus and moulds

3. Use appropriate scientific equipment and improvise using alternative equipment.

4. Collect mathematical data that will help students describe the biodiversity in a compost bin.

5. With an entire class working on the activity, how will they know how many species have been observed?

6. How can they estimate a comparative number of organisms?

For this activity:

If an insect looks different to other insects it is recorded as a different species. Provided all the surveys are consistent it won’t matter if some of the insects are different looking larvae compared to the adult.
If a mould looks different or grows in a very different way it is recorded as a separate species.
Students should wear disposable gloves and should not do sniff tests on the compost.
Teachers may prefer to give students samples in contained petrie dishes and use wooden skewers to probe the compost.
The class could divide the sample into two and estimate the comparative number of the most common organisms in the large sample while the rest of the class separates out species.
A large number of petrie dishes could be available for students to put representative creatures into. Then, place the animals and moulds in petrie dishes so they can be sorted.

To identify groups of animals that live in compost bins you could use theSlugs And Bugs Identification Chart.

Reflection

Ask students to complete the Reflection Questions on the Student Worksheet. These can form the basis of the class discussion.

Extension

Ask students to draw one of the creatures they see, using scientific drawing conventions. Students can use the Scientific drawing guidelines to help them with their drawings.

Species Diversity in a Compost Bin

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