This is where the model earns its keep — explaining the Australian bush you've grown up in, and then the real test: being handed a population crash and reasoning back to the cause.
Why Dingoes Keep the Outback in Balance
Out in the rangelands, dingoes sit near the top of the web, eating kangaroos and rabbits. That sounds like bad news for the kangaroos — but pull the dingoes out (as graziers once did across huge areas) and something unexpected happens: kangaroo and rabbit numbers explode, they strip the ground bare of plants, the soil erodes, and smaller native animals lose their cover and food and crash. The predator wasn't just a killer — it was a brake on the whole system. This is a top-down effect: take away the top, and the levels below run wild.
When a Web Gets a Stranger: the Cane Toad
In 1935 cane toads were released in Queensland to eat beetles in the cane fields. They barely touched the beetles — but they bred in their millions, marched west, and they're poisonous. Quolls, goannas and snakes that tried to eat them died. So predators the toad never replaced simply vanished from stretches of the web, and everything those predators used to keep in check shifted. One introduced species, dropped into a web with no natural controls, rewired ecosystems across half a continent.
The Real Skill: Reasoning Backwards from a Crash
Rung 2 went forwards — who eats whom. Mastery is going backwards: you're handed a population crash and you reconstruct the cause. A grazier reports the small native mammals on his land have all but disappeared. Work back: something that protected them was removed, or something that hunts them was added — dingoes culled, so foxes and cats moved in unchecked, or rabbits stripped their habitat bare. A river's fish are dying off though the water looks clean. Work back up the web: maybe the insects they eat have collapsed, or a plant lower down has been cleared. Each crash has a cause sitting somewhere in the web — your job is to trace the threads back to it. Take on the scenario cards in the toy and talk each one through the web.
A Depth-study Thread
This is a lovely launch pad for a Year 8 depth study (the scope sets aside time for one): map a real local food web — pick a patch of bush, a creek or even the schoolyard, list what lives there and who eats whom, and draw the web with the arrows pointing the right way. Or model a single predator–prey relationship over time (foxes and rabbits is the classic) and watch the two populations rise and fall in step. It's real working scientifically (SC4-WS-05, SC4-WS-08) hanging off an ecology idea.