Ecosystems · Écosystèmes
| English | Français |
|---|---|
| ecosystem/ˈiːkəʊsɪstəm/ | écosystème |
| producers/prəˈdjuːsəz/ | les producteurs |
| consumers/kənˈsuːməz/ | les consommateurs |
| decomposers/ˌdiːkəmˈpəʊzəz/ | décomposeurs |
| biodiversity/ˌbaɪəʊdaɪˈvɜːsɪti/ | biodiversité |
Follow the arrows and the supplied energy
- An invented meadow budget gives grass 5,000 J, grasshoppers 600 J and frogs 60 J over the same stated period. Food-chain arrows run from food to consumer: grass → grasshopper → frog.
- An ecosystem 生态系统 includes organisms and nonliving conditions. The energy numbers do not give population sizes or predict an exact future decline.
Identify the roles before calculating
- Producers · Producteurs 生产者 make organic material using an energy source. Consumers · Consommateurs 消费者 obtain it from other organisms; a consumer may have several food sources in a wider food web.
- Decomposers 分解者 break down dead material and waste, helping return nutrients to available forms. Their role is different from recreating energy for producers.
Calculate each transfer separately
- Transfer efficiency follows $\eta=(E_{\text{next}}/E_{\text{previous}})\times100\%$. The first transfer gives $\eta=(600/5000)\times100\%=12\%$.
- The second gives $\eta=(60/600)\times100\%=10\%$. Use the correct previous level as the denominator; a 10% assumption is not a universal ecological rule.
Grass supplies 5000 J and grasshoppers receive 600 J over the stated period. What is transfer efficiency as a percentage number?
η = 600/5000 × 100 = 12%.
Frogs receive 60 J from the original 5000 J grass budget. What percentage of that original energy is this?
60/5000 × 100 = 1.2%; this is across both transfers, not one transfer.
Explain why energy available declines
- Organisms use energy in respiration, and energy is dissipated to the surroundings. Some material is not eaten or assimilated, so not all previous-level energy reaches the next consumer level.
- Energy does not disappear from existence. Its transfer and dissipation differ from nutrient cycling, and the budget alone does not establish a universal maximum food-chain length.
A separate toy model explicitly assumes 10% at each transfer: 10,000 → 1,000 → 100 → 10 energy units. The third consumer receives 10 units under that assumption; do not substitute those percentages for the meadow's supplied values.
In an illustrative model only, producers have 10000 energy units and exactly 10% reaches each next level. How many units reach the third consumer level?
Under that explicit assumption, 10000 → 1000 → 100 → 10. This is a toy calculation, not a universal ecosystem efficiency or maximum-chain rule.
Which explanation appropriately describes declining energy available along a defined food chain?
Explain the processes and supplied budget. Transfer efficiencies vary, and an energy argument does not establish a fixed universal limit on chain length.
Separate matter cycling from variety of life
- Matter can cycle through organisms, soil, air and water, while a local ecosystem can also gain or lose matter across its boundary. “Cycles” does not mean every local stock stays constant.
- Biodiversity · Biodiversité 生物多样性 concerns variety of life and can use several measures. A count of grasshoppers describes one species' abundance, not the meadow's whole variety.
Match each to how it moves through an ecosystem.
Energy transfers and dissipates; nutrients and other matter can cycle. Local systems may also exchange matter across their boundaries.
Explain why a count of grasshoppers alone cannot establish the biodiversity of the meadow.
Example: “A grasshopper count describes one species, not the variety and distribution of organisms in the meadow.”
Matter cycling proves that the amount of matter inside a local ecosystem can never change.
False: matter may cross its boundary.
Limit the conclusion to the record
- Report the observed energy levels, period and calculated efficiencies. To investigate population change, collect comparable population records and information about other food sources and conditions.
- Keep the food-chain arrows, energy budget, nutrient cycles and diversity measures distinct. A claim about one does not automatically establish the others.
Use the supplied denominator at each transfer. Explain energy dissipation without saying energy is destroyed or indefinitely recycled back to producers.
Decomposers destroy matter and recreate energy for producers.
They break down dead material and help return nutrients to available forms. Matter cycling differs from indefinite recycling of energy.