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## 'Food Web' printed from http://nrich.maths.org/

### Why do this problem?

This problem provides a realistic context in which students will need to use the information provided to determine the sustainability of a simple eco-system.

Students will need to use a combination of argument and calculation to come to a view on this.

### Possible approach

Starting with the food web - an interconnected food chain, in which arrows show the direction of energy transfer - is a straight-forward way for students to work through the information about what animal eats what.

The first discussion questions then lead them into considering what happens if one species or another increases or decreases.

The factual information can then be brought into the discussion.

### Key questions

Are there any species which could be removed from this food web without it falling apart?

Which species provides the crucial link holding this food web together?

Why is the size of this population critical?

### Possible extension

What is the smallest population size of eg. rabbits, which makes the eco-system viable?

### Possible support

Show students examples of food webs and discuss which species are critical and which could be removed without consequence.