Food chains and predator–prey cycles
| English | 中文 | Pinyin |
|---|---|---|
| producer/prəˈdjuːsə/ | 生产者 | shēng chǎn zhě |
| primary consumer/ˈpraɪməri kənˈsuːmə/ | 初级消费者 | chū jí xiāo fèi zhě |
What would explain this observation?
- A food-chain arrow points from the organism eaten towards the eater. Reversing it changes the feeding relationship being shown.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Photosynthetic plants and algae are producers 生产者: they make glucose and other molecules that form biomass. Producers begin the specified food chains. Primary consumers 初级消费者 eat producers, secondary consumers eat primary consumers and tertiary consumers eat secondary consumers. Predators kill and eat prey; the same organism can be a consumer in more than one feeding route.
- producer: An organism making organic molecules, usually by photosynthesis in this course; primary consumer: An organism feeding on producers.
In grass → rabbit → fox, what does the arrow from grass to rabbit show?
In a stable community, prey and predator numbers can rise and fall in cycles. More prey can support more predators after a delay; greater predation can reduce prey, followed by fewer predators when food is scarce. The pattern is a model affected by other food, disease, migration and environmental factors.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- In a stable community, prey and predator numbers can rise and fall in cycles. More prey can support more predators after a delay; greater predation can reduce prey, followed by fewer predators when food is scarce. The pattern is a model affected by other food, disease, migration and environmental factors.
- Read the arrow key, identify each feeding step and interpret population graphs by axes and peaks. Compare the timing of prey and predator peaks instead of assuming simultaneous changes. Use supplied data; observations should not involve harming organisms to demonstrate feeding.
Which two habits make the investigation or model in this case more defensible?
Read the arrow key, identify each feeding step and interpret population graphs by axes and peaks. Compare the timing of prey and predator peaks instead of assuming simultaneous changes. Use supplied data; observations should not involve harming organisms to demonstrate feeding.
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 fictional prey peak occurs at month 4 and a predator peak at month 6. Lag = 2 months. This does not mean the predator count must equal the prey count or that every ecosystem has a two-month cycle. Read each curve’s units and scale before comparing magnitudes.
Prey peaks at month 7 and predators at month 10 in a supplied graph. Find the lag. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Prey peaks at month 7 and predators at month 10 in a supplied graph. Find the lag.
The result is 3 months. Known: a fictional prey peak occurs at month 4 and a predator peak at month 6. Lag = 2 months. This does not mean the predator count must equal the prey count or that every ecosystem has a two-month cycle. Read each curve’s units and scale before comparing magnitudes.
Check the conclusion and its limits
- Plants also respire, but photosynthesis makes them producers in this model. A predator may have predators of its own. Population cycles do not imply that every prey death is due to the named predator or that extinction must follow a trough.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Predator and prey peaks must always occur at the same time. This claim is false: Plants also respire, but photosynthesis makes them producers in this model. A predator may have predators of its own. Population cycles do not imply that every prey death is due to the named predator or that extinction must follow a trough.
Food chains and predator–prey cycles: In a stable community, prey and predator numbers can rise and fall in cycles. More prey can support more predators after a delay; greater predation can reduce prey, followed by fewer predators when food is scarce. The pattern is a model affected by other food, disease, migration and environmental factors.
Predator and prey peaks must always occur at the same time.
Plants also respire, but photosynthesis makes them producers in this model. A predator may have predators of its own. Population cycles do not imply that every prey death is due to the named predator or that extinction must follow a trough.
An organism making organic molecules, usually by photosynthesis in this course: write the technical term.
producer means An organism making organic molecules, usually by photosynthesis in this course.