Food Chains and Food Webs
Introduced| English |
|---|
| food chain/fuːd tʃeɪn/ |
| food web/fuːd web/ |
| keystone species/ˈkiːstəʊn ˈspiːsiːz/ |
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 chain shows…
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…
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.
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.
Because the web is interconnected, losing one species ripples through many others.
Select all true statements about food chains and webs.
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.