Trophic levels and extracellular decomposition
| English | 中文 | Pinyin |
|---|---|---|
| trophic level/ˈtrəʊfɪk ˈlevl/ | 营养级 | yíng yǎng jí |
| extracellular digestion/ˌekstrəˈseljʊlə daɪˈdʒestʃn/ | 细胞外消化 | xì bāo wài xiāo huà |
What would explain this observation?
- A decomposer acts on dead material from several trophic levels 营养级. It is not simply the next predator above an apex consumer.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Trophic level 1 contains producers such as plants and algae. Primary consumers at level 2 eat producers; secondary consumers at level 3 eat primary consumers; tertiary consumers at level 4 eat secondary consumers. An apex predator has no predators in the stated ecosystem. Level refers to a feeding position rather than size or intelligence.
- trophic level: An organism’s feeding position along a stated food chain; extracellular digestion 细胞外消化: Enzyme digestion outside cells before products are absorbed.
Where do decomposer enzymes first act in this account?
Decomposers break down dead plants, animals and waste. They secrete enzymes into their surroundings; enzymes digest large molecules into small soluble products that diffuse into the microorganism. This extracellular digestion lets material from several levels return to the system through microbial activity and material cycling.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Decomposers break down dead plants, animals and waste. They secrete enzymes into their surroundings; enzymes digest large molecules into small soluble products that diffuse into the microorganism. This extracellular digestion lets material from several levels return to the system through microbial activity and material cycling.
- Label a supplied food chain and use the arrow legend to identify feeding positions. In a food web an organism may occupy different positions along different routes. Trace dead material separately to decomposers. Use prepared diagrams rather than feeding experiments or unknown microbial cultures.
Which two habits make the investigation or model in this case more defensible?
Label a supplied food chain and use the arrow legend to identify feeding positions. In a food web an organism may occupy different positions along different routes. Trace dead material separately to decomposers. Use prepared diagrams rather than feeding experiments or unknown microbial cultures.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a model chain contains grass → insect → bird → hawk. Grass is level 1, insect level 2, bird level 3 and hawk level 4. There are three feeding transfers from grass to hawk. The number of transfers is one less than the number of levels in this linear chain.
A linear chain has five feeding levels. Find the number of transfers from first to last. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A linear chain has five feeding levels. Find the number of transfers from first to last.
The result is 4 transfers. Known: a model chain contains grass → insect → bird → hawk. Grass is level 1, insect level 2, bird level 3 and hawk level 4. There are three feeding transfers from grass to hawk. The number of transfers is one less than the number of levels in this linear chain.
Check the conclusion and its limits
- Carnivore does not always mean level 3: a carnivore eating another carnivore can be level 4. Enzymes act outside a decomposer before soluble products enter it. The apex label depends on the supplied ecosystem, not a universal claim about the species.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Every carnivore must occupy trophic level 3. This claim is false: Carnivore does not always mean level 3: a carnivore eating another carnivore can be level 4. Enzymes act outside a decomposer before soluble products enter it. The apex label depends on the supplied ecosystem, not a universal claim about the species.
Trophic levels and extracellular decomposition: Decomposers break down dead plants, animals and waste. They secrete enzymes into their surroundings; enzymes digest large molecules into small soluble products that diffuse into the microorganism. This extracellular digestion lets material from several levels return to the system through microbial activity and material cycling.
Every carnivore must occupy trophic level 3.
Carnivore does not always mean level 3: a carnivore eating another carnivore can be level 4. Enzymes act outside a decomposer before soluble products enter it. The apex label depends on the supplied ecosystem, not a universal claim about the species.
An organism’s feeding position along a stated food chain: write the technical term.
trophic level means An organism’s feeding position along a stated food chain.