Energy Flow Through Ecosystems
| English | Chinese | Pinyin |
|---|---|---|
| producer | 生产者 | shēng chǎn zhě |
| food chain | 食物链 | shí wù liàn |
| consumer | 消费者 | xiāo fèi zhě |
| trophic level | 营养级 | yíng yǎng jí |
Energy enters as sunlight
- Almost every ecosystem runs on energy from the Sun.
- Plants capture that light and lock it into food.
- From there, energy flows from one living thing to the next.
- But at every step, most of it is lost.
Producers capture the energy
- A producer 生产者 makes its own food using sunlight — a green plant.
- Producers form the base of every food chain.
- They store the Sun's energy as chemical energy in sugar.
- Everything else in the ecosystem depends on this stored energy.
Where does the energy in most ecosystems originally come from?
Sunlight is captured by producers (plants) through photosynthesis, feeding the whole ecosystem.
A producer in an ecosystem is an organism that…
A producer makes its own food (photosynthesis); consumers eat other organisms.
Consumers and trophic levels
- A consumer 消费者 eats other organisms to get energy.
- Each feeding step is a trophic level 营养级: producer, then primary consumer, then secondary, and so on.
- Energy passes up a food chain 食物链 from level to level.
- But only a fraction of it makes it to the next step.
Build the pyramid of energy
Drag the energy the plants capture and watch only a tenth pass up each level - so the top predator is left with almost nothing.
If a trophic level holds 10000 units of energy, roughly how many pass to the next level (about 10%)?
About 10% passes up each step, so $10000 \times 0.1 = 1000$ units reach the next level.
Each feeding step in a food chain — producer, then consumer — is a ____ level.
A trophic level is one feeding step; energy falls at each higher level.
The ten-percent rule
- At each step, only about 10% of the energy passes on.
- The rest is lost, mostly as heat from respiration.
- So each higher level holds far less energy than the one below.
- This is why food chains are short and top predators are rare.
Select all true statements about energy flow.
Energy is lost at each step (as heat), not recycled without loss. The other three are correct.
Energy is not recycled through a food chain — it is steadily lost. About 90% is used up or lost as heat at every step, and only ~10% passes on. Unlike nutrients, energy makes a one-way trip and must be constantly resupplied by the Sun.
Following 10,000 units of energy:
- Plants capture 10,000 units of the Sun's energy.
- The primary consumers that eat them get about 1,000 (10%).
- The secondary consumers get about 100 — so little is left that a fourth or fifth level can barely be fed.
Energy enters an ecosystem as sunlight, captured by producers. It flows up a food chain through consumers, one trophic level at a time. Only about 10% passes to each higher level — the rest is lost as heat — so food chains are short and top predators are few.