Food Chains and Food Webs
Introduced| English | Meaning |
|---|---|
| food chain/fuːd tʃeɪn/ | A sequence showing how energy and matter pass through feeding relationships from one organism to another. |
| food web/fuːd web/ | A network of interconnected feeding relationships in an ecosystem. |
| keystone species/ˈkiːstəʊn ˈspiːsiːz/ | A species whose effect on an ecosystem is unusually large relative to its abundance. |
Mapping who eats whom
- To understand an ecosystem, we track where its energy goes.
- The simplest picture is a straight line from plant to predator.
- But real life is far more tangled than a single line.
- Two tools — food chains and food webs — capture both views.
A food chain: one path
- A food chain 食物链 shows a single path of energy.
- For example: grass → grasshopper → frog → snake.
- Each arrow points the way energy flows, from prey to predator.
- It is a simple, clear way to show one feeding route.
A food web: arrows show energy flowing to the eater
A food chain shows…
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A food chain is one straight path of energy: producer → consumer → consumer.
A food web: many paths
- Most animals eat more than one thing and are eaten by more than one.
- A food web 食物网 links many food chains together.
- It shows all the overlapping feeding paths in an ecosystem.
- A web is a much more realistic picture than a single chain.
Energy along a food chain
Follow energy from producers up the chain, losing about 90% at each link.
A food web is…
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A food web links many overlapping food chains, showing the many feeding paths in an ecosystem.
Real ecosystems are better described as food ____ than single chains.
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Most animals eat several things and are eaten by several, so a web is more realistic than a chain.
Everything is connected
- Because a web is interconnected, its species depend on one another.
- Removing one species can ripple through many others.
- A keystone species 关键种 has an especially large effect for its size.
- Lose it, and the whole web can be thrown out of balance.
Removing one species from a food web can affect many other species.
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Because the web is interconnected, losing one species ripples through many others.
Select all true statements about food chains and webs.
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Real ecosystems are complex webs, not single chains. The other three are correct.
A single food chain is a simplification. Real ecosystems are food webs, because almost no animal eats just one thing. Always remember the web behind the chain — pulling on one strand tugs many others.
Remove the sea otters:
- In a kelp forest, otters eat sea urchins, and urchins eat kelp.
- Remove the otters and the urchins multiply, stripping the kelp bare.
- Fish, seals, and many other species that depend on the kelp then decline — one change, felt across the whole web.
A food chain shows a single path of energy (producer → consumer → consumer). A food web links many chains, giving a realistic picture of an ecosystem's feeding paths. Because the web is interconnected, removing one species — especially a keystone species — can affect many others.