Ecosystems
| English | Chinese | Pinyin |
|---|---|---|
| ecosystem | 生态系统 | shēng tài xì tǒng |
| producers | 生产者 | shēng chǎn zhě |
| consumers | 消费者 | xiāo fèi zhě |
| decomposers | 分解者 | fēn jiě zhě |
| biodiversity | 生物多样性 | shēng wù duō yàng xìng |
Energy flows through; matter goes round
- An ecosystem 生态系统 is the organisms in an area plus the non-living conditions they live in.
- Producers 生产者 make their own food from sunlight. Consumers 消费者 eat others. Decomposers 分解者 return nutrients to the soil.
- The two verbs matter: energy flows through and is lost; matter cycles and is reused.
Match each to how it moves through an ecosystem.
The two verbs carry the whole unit. Sunlight arrives continuously; atoms do not.
Why food chains are short
- About 90% of the energy at each level is lost — as heat, and in the work of staying alive.
- After four transfers roughly one part in ten thousand of the original energy remains.
- That is not enough to support another level of predators, which is why a chain of five links is already unusual.
Biodiversity
- Biodiversity 生物多样性 is the variety of life in an ecosystem.
- It matters because variety is what lets an ecosystem absorb change: if one species fails, another can do its job.
- ⚠ An ecosystem with one dominant species is productive and fragile, and the fragility only shows when something goes wrong.
In one sentence, explain why an ecosystem with one dominant species is fragile.
Example: "If a disease reaches the dominant species there is no other species able to fill its role, so the whole system changes at once."
Why there are no fifth-level predators.
Start with 10,000 units of energy captured by plants.
Herbivores get about 1,000. Their predators get 100. The next level gets 10. The next would have 1.
An animal cannot live on a thousandth of what the plants captured, so the chain stops — and this is an energy argument, not an ecological accident.
Plants capture 10000 units. Roughly how many units reach the third consumer level?
About 90% is lost at each transfer: 10000 → 1000 → 100 → 10.
Answer food-chain questions in energy terms. "There is not enough food" is the observation; "about 90% is lost at each transfer, so the fifth level has too little to sustain a population" is the explanation, and only the second earns the marks.
Which answer explains why food chains are short?
The first is the observation. Only the energy argument is the explanation.
Do not say that decomposers "get rid of" waste. They return nutrients to the soil, which is the step that closes the matter cycle — without them the nutrients would be locked in dead material and the producers would stop.
Decomposers mainly get rid of waste.
They return nutrients to the soil, closing the matter cycle. Without them producers would stop.