Food Chains and Food Webs
In 2016, CSIRO researchers mapping a Tasmanian kelp forest documented a food web involving more than 200 species — and showed that removing just 1 urchin species caused the entire web to collapse.
Printable Worksheets
Print or save as PDF — or build a custom worksheet from any module's questions.
Q1 · Quickly write a food chain with at least 4 living things in it. Start with a plant.
Q2 · In the chain "grass → kangaroo → dingo", which way do you think the ARROW should point — toward the eater or toward the eaten? Why?
● Know
- A food chain is a linear sequence showing energy moving from one organism to the next
- Arrows in a food chain point from food → eater (the direction energy flows)
- Trophic levels: producer → primary consumer → secondary consumer → tertiary consumer
● Understand
- Why energy flows from prey to predator (not the other way)
- Why a food web is more realistic than a single chain
- Why removing one species can affect many others in a web
● Can do
- Draw a food chain with arrows in the correct direction
- Identify the trophic level of any organism in a chain
- Draw a simple Australian food web from a list of species
- Food chain
- Food web
- Trophic level
- Producer
- Consumer
- Makes its own food, usually by photosynthesis
- A linear sequence of arrows from food to eater
- Eats other organisms for energy
- Many food chains joined together
- An organism's position in the chain (1st, 2nd, 3rd…)
Walk through any patch of Australian bush and you are surrounded by feeding relationships: a caterpillar chews on a gum leaf, a thornbill snatches the caterpillar, a currawong takes the thornbill — energy flowing from leaf to bird in a three-step chain.
Grass → Kangaroo → Dingo
The arrow always means "is eaten by" — or, more precisely, "energy flows in this direction". Grass uses sunlight to make food. A kangaroo eats the grass and gets the energy. A dingo eats the kangaroo and gets some of that energy.
Each organism has a trophic level, which is just a fancy name for its position in the chain:
| Trophic level | Role | Example from this chain |
|---|---|---|
| 1st | Producer | Grass |
| 2nd | Primary consumer (herbivore) | Kangaroo |
| 3rd | Secondary consumer (carnivore) | Dingo |
A longer chain might add a 4th level (tertiary consumer) — for example, a wedge-tailed eagle that eats young dingoes.
In the chain grass → kangaroo → dingo, the grass is the , the kangaroo is the consumer and the dingo is the consumer. Arrows show the direction flows.
Wrong: "The arrow points toward what gets eaten because the predator is hunting it." Half the class draws their arrows the wrong way every single year. The arrow follows the energy, not the predator.
Right: The arrow always points from the food TO the eater — same direction as the energy flowing into the eater's body.
Wrong: "Food chains start with the sun." The sun is the source of energy but the sun is not a living organism. Chains start with a producer (a plant, algae or photosynthetic bacterium).
Right: Food chains always start with a producer (1st trophic level). The sun is the energy source but is not in the chain itself.
Wrong: "Food webs and food chains are the same thing." A food chain is a single straight line. A food web is lots of chains joined together — much more like a real ecosystem.
Right: Chain = one straight line. Web = many connected chains. Real ecosystems are webs.
Real animals eat more than one thing, and most are eaten by more than one predator. A food web shows this honestly. Look at these three small Australian chains:
- Gum leaves → koala → dingo
- Grass → kangaroo → dingo
- Grass → grasshopper → magpie → wedge-tailed eagle
Some species appear in more than one chain — grass feeds both kangaroos and grasshoppers, dingoes eat both koalas and kangaroos. Joining the chains gives a food web:
| Producer (1st level) | Primary consumer (2nd) | Secondary consumer (3rd) | Tertiary consumer (4th) |
|---|---|---|---|
| Gum leaves | Koala | Dingo | — |
| Grass | Kangaroo | Dingo | — |
| Grass | Grasshopper | Magpie | Wedge-tailed eagle |
Now if a fire wipes out the grass, three chains are affected, not one. That's the power of looking at the whole web.
A food chain is useful but it pretends every animal only eats one thing. A food web shows the truth:
- A dingo eats kangaroos, wombats, possums, lizards and rabbits — not just one species.
- A kangaroo is hunted by dingoes, wedge-tailed eagles (when young) and sometimes humans.
- Grass feeds kangaroos, wombats, grasshoppers, sheep and more.
Because everything connects to everything else, food webs make a much better prediction tool. If feral rabbits move in and out-eat the kangaroos, dingoes don't just starve — they switch to rabbits, possums and lizards. A single food chain would miss that flexibility.
Because everything in a web is connected, removing one species ripples through. Two real examples:
- Dingoes removed from a NSW grassland. Kangaroo numbers explode (no predator). They overgraze the grass. Grass dies back, the soil erodes, and many other grass-eating species (grasshoppers, smaller marsupials) lose food.
- Rabbits introduced to Australia. Rabbits compete with kangaroos and wombats for grass. They also feed dingoes and wedge-tailed eagles, propping up predator numbers, which then puts even more pressure on native marsupials.
The big idea: a food web isn't just a drawing — it's a way of predicting what will happen if something changes.
Consider the food chain: gum leaves → koala → dingo. Predict which way the ARROWS should point and explain WHY they point that way in one sentence. Lock in your prediction, then reveal.
How close was your prediction?
Excellent — you nailed the "arrow = energy flow" idea.
Good to learn now — arrows = direction of energy, not direction of hunting.
Earlier you were asked: In grass → kangaroo → dingo, which way does the arrow point — toward the eater or toward the eaten, and why?
Now write a fuller answer. Mention "energy flow", give the correct arrow direction, and explain why drawing arrows the wrong way would be a physical mistake.
Q1. Draw a 4-step Australian food chain (use arrows). Label each organism with its trophic level. (3 marks)
Q2. Explain why food chain arrows point from food to eater. Use the words "energy", "producer" and "consumer" in your answer. (4 marks)
Q3. A student says "A food chain and a food web show the same information, so it doesn't matter which one we use." Evaluate this claim using an Australian example. (4 marks)
Answers
▾MCQ 1
B — The arrow shows the direction energy flows. Kangaroo → dingo means the dingo eats the kangaroo and gets its energy. A is the opposite direction; C is wrong (different trophic levels); D is irrelevant.
MCQ 2
C — The magpie eats the grasshopper (a primary consumer), so the magpie is a secondary consumer (3rd trophic level). The wedge-tailed eagle then eats the magpie, making the eagle the tertiary consumer.
MCQ 3
D — A food web is many chains joined because most species have multiple food sources and multiple predators. A describes a chain; B and C are wrong.
MCQ 4
A — A food chain starts with a producer (the only organism that can capture energy from a non-living source — sunlight). The sun is the energy source but is not itself in the chain. Herbivores and predators come after producers.
MCQ 5
B — Without dingoes, kangaroos lose their main predator and breed up. Too many kangaroos overgraze the grass, leaving less food for grasshoppers, wombats and other grass-eaters. A is wrong (knock-on effects); C and D are not physical possibilities.
Short Answer 1
Model answer: grass (1st, producer) → grasshopper (2nd, primary consumer) → magpie (3rd, secondary consumer) → wedge-tailed eagle (4th, tertiary consumer). Award 1 mark for correct arrow direction (food → eater), 1 for starting with a producer, 1 for all four trophic levels correctly named. Accept other valid Australian chains.
Short Answer 2
Model answer: Food chain arrows point from food to eater because they show the direction energy flows through the ecosystem. A producer (like grass) captures energy from sunlight and stores it in its cells. When a consumer (like a kangaroo) eats the producer, that energy moves from the grass into the kangaroo's body, so the arrow points from grass → kangaroo. If we drew the arrow the other way, we would be saying the kangaroo gave its energy to the grass, which never happens. 1 mark each for: arrow direction stated correctly; "energy" used correctly; "producer" used correctly; "consumer" used correctly.
Short Answer 3
Model answer: The student is wrong. A food chain shows only one straight line of feeding, but real species eat many things. For example, in a NSW grassland a dingo eats kangaroos, wombats and rabbits — not just one — and grass is eaten by kangaroos, wombats and grasshoppers. A food web shows all these connections, so if rabbits arrive or dingoes are removed, you can predict how all parts of the web are affected. A food chain alone would miss this and give the wrong predictions. 1 mark for stating the claim is wrong, 1 for naming a specific multi-source eater, 1 for the prediction-power point, 1 for a clear Australian example throughout.