Teacher Preparation

Overarching learning goals: The aim of this activity is for students to design an investigation to find out how a species' diversity is affected by habitats around the school. Students will identify different habitats around the school and the way these habitats relate to local food webs. They will also link these habitats with different types of ecosystems.

Teacher content information: Food chains are a linear way to show the feeding relationships in an ecosystem. An animal grazes on the plant. Another, usually larger, animal eats the animal browser, and so on in a chain. The plant gets its energy using sunlight to make food. The browsing animal gets its energy from eating plants. The predators get their food from eating animals. We can use an arrow to show this relationship. It is important to note that the arrow always points to the animal that has just eaten something. This is because it shows the flow of energy. For example, the browsing animal eats the plant so the energy from the plant flows to the browsing animal, thus the arrow would point at the animal.

But nature isn’t as simple as a food chain. Relationships in nature are complex and involve all sorts of interconnections and energy flows that are best shown as a food web.

Student and classroom organisation

Step 1.

An introduction to food webs and food chains.

Begin this activity by sharing and discuss the following information with your students (these images are also available on the student worksheet).

A food chain shows the feeding relationships between plants and animals. A food chain is organised into a linear form and shows the flow of energy between organisms. Plants are at the beginning of the food chain and they get their energy from sunlight. The browsing animal gets its energy from eating the plants. The predators get their food from eating other animals. We can use an arrow to show these relationships. It is important to note that the arrow always points to the animal that has just eaten something, as this shows the flow of energy. For example, the browsing animal eats the plant so the energy from the plant flows to the browsing animal, thus the arrow would point at the animal.

But nature isn’t as simple as a food chain. Relationships in nature are complex and involve all sorts of interconnections and energy flows that are best shown as a food web. The picture below shows an Antarctic food web.

You can see from this food web that the flows of energy go in all sorts of directions and weave and wind around each other. You can also see that generally the smaller animals at the bottom of the food web have a greater number of predators, and the number of predator-prey relationships decreases the further up the food web you go.

Step 2.

Show the flow of energy

In this part of the activity students can work from the Student Worksheet.

Ask students to experiment with identifying energy flows in the bush food web on their Student Worksheet. They should ensure that the arrows point in the correct direction (answers at end of the Teacher Worksheet).

Discuss the food webs. Consider the following questions (answers included where appropriate):

Which parts of the food web did they find difficult or challenging?
Which species are at the top of the food chain and which are at the bottom - is there a pattern? – Organisms at the bottom of the food chain tend to be smaller and are consumed by many species. Those at the top tend to be carnivores with few predators and many types of prey.
Organisms on a food web are generally classified as being a producer, consumer or a decomposer. Producers are organisms that produce energy, generally through photosynthesis (such as plants and algae). Consumers are those consume energy through food (all animals, including humans). Decomposers are those that break down plant and animal wastes and release it again as energy (such as bacteria and fungi). Which organisms on the food web are producers, consumers and decomposers?

Also ask students to think about how indigenous and introduced species affect food webs.

What is an indigenous organism? – An indigenous organism is a plant or animal that occurs naturally in an area.
What is an introduced organism? – An introduced organism (also known as ‘feral’) is one that is brought into an area to which it doesn’t naturally belong.
What role do indigenous organisms play in the food web? - Indigenous species have evolved with the ecosystem for thousands of years and are critical to the health and balance of food webs. For example, an indigenous skink will eat indigenous insects and be eaten by indigenous birds (like a kookaburra).
What role do introduced organisms play in the food web? -
Introduced species upset the balance of food webs by producing energy that can’t be absorbed or by consuming energy that is required by other organisms. For example, an introduced tree has flowers, seeds and leaves that aren’t as tasty as those from an indigenous tree so don’t get eaten so may spread rapidly, stifling the growth of indigenous trees. An introduced animal such as a fox eats smaller mammals that are also the prey of the Spotted Quoll (Australia’s largest indigenous carnivore), meaning there will be fewer animals for the Quoll.

Step 3.

What kinds of food webs might exist at your school?

Students head outside and look for plants and animals around the schoolyard. Students can record the results in Table 1 on the Student Worksheet. Students will probably be drawn to the bigger species, such as birds and trees, but remind them that smaller organisms such as fungi, lichen and insects are critical parts of the food web. To avoid complexity, ask students to limit the number of type of organisms that they find to ten (see sample table at end of teacher information).

As they go, ask students to think about how the organisms that they identify (both indigenous and introduced) might fit into the local food web.

If there are any gaps on the tables, ask students to undertake some research on the internet to fill in these blanks. Consider suggesting that students take photos to help with identification.

Step 4.

Create your own food web

Using the organisms identified in the schoolyard ask students to create their own food web. Students can either draw their food webs or create them by sticking photos of organisms on butcher’s paper and adding the arrows. Students should include the common names for each organism on their food web. Remind students that the arrows should indicate the direction of the flow of energy.

Step 5.

Closing discussion

Ask students to present their food webs for discussion. Consider the following questions:

Which organisms were the easiest to place in the food web?
Which were the hardest?
What do you think the number of organisms for each type tells us about that organism?
What do they think the role is of introduced species in the schoolyard food web?
How healthy do they consider the schoolyard food web to be?
How could the health of the schoolyard food web be improved?

Extension Activity A: Using scientific names

Create the food webs using scientific names of organisms. Students will need to conduct some research to fing the scientific names of local species.

Extension Activity B. Food chain glossary

Like many of the big ideas in science, big words and jargon can make grappling with food chains and webs a bit of a drag. In this exercise students investigate the food chain lingo and create a glossary of these words.

Ask students to research and create their own definitions for the following terms:

Food chain
Food web
Producer
Consumer
Decomposer
Herbivore
Carnivore
Omnivore
Predators
Apex predators
Trophic levels

Appendix

Sample table

Ask students to use the following headings for their own tables, and to limit the number of types of organisms to ten.

Common name of organism	Indigenous or introduced	Where found	Behaviour (where applicable)	Producer, consumer or decomposer	Where it gets its energy	How many found
e.g. 1. River red gum	Indigenous	Gully	N/A	Producer	Sunlight	2
e.g. 2. Common myna	Introduced	Oval	Feeding	Consumer	Insects	7
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Schools Tree Day - Schoolyard food webs

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