Higher Tier: interacting factors and greenhouse decisions
הוצג| English | משמעות |
|---|---|
| limiting factor/ˈlɪmɪtɪŋ ˈfæktə/ | גורם מגביל |
| inverse-square relationship/ɪnˈvɜːs skweə rɪˈleɪʃənʃɪp/ | יחס הפוך-ריבועי |
What would explain this observation?
- Higher Tier: A greenhouse can spend more on lighting without growing more crop. A useful decision checks which factor limits the response and whether extra revenue exceeds extra cost.
Build the model
- Photosynthesis factors interact: light, carbon dioxide or temperature can limit rate under a particular set of conditions.
- Increasing a factor that is not currently limiting may produce no gain.
- On a graph, compare curves at the same value of the horizontal variable and use the stated changed condition to explain differences.
- limiting factor 限制因素: A condition whose shortage restricts the process rate.
- inverse-square relationship 平方反比关系: A relationship in which a quantity varies as one divided by distance squared.
What does doubling distance do to ideal point-source light intensity?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Light intensity from a point source follows an inverse-square law: doubling distance quarters the intensity. Photosynthesis responds to intensity only while light is the limiting factor, so no automatic doubling follows.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- For the ideal point-source model, light intensity is proportional to 1/distance².
- Doubling distance makes intensity one quarter, not one half.
- Real lamp geometry and reflections can depart from this approximation.
- A greenhouse decision compares added revenue with added lighting, heating or carbon dioxide costs; maximum photosynthesis rate need not give maximum profit.
In the lab: Inspect supplied curves with one controlled change between them. Identify evidence that a proposed limiting factor matters at a particular point. Calculate relative intensity using a stated reference distance, then evaluate a fictional greenhouse budget. These calculations extend RP6 interpretation but do not justify uncontrolled heating or added gases in a classroom.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: intensity is 100 relative units at 20 cm.
- At 40 cm the ideal model predicts 100×(20/40)² = 25.
- Separately, a greenhouse change adds 180 revenue units but 120 cost units, so added profit is 60.
- A second change adding 40 revenue and 70 cost reduces profit by 30 even if photosynthesis increases.
Your turn: Intensity is 144 units at 10 cm. Calculate ideal intensity at 30 cm.
Intensity is 144 units at 10 cm. Calculate ideal intensity at 30 cm.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 16 relative units. Known: intensity 144 units at 10 cm; inverse-square model. At 30 cm the distance is 3 times greater, so intensity = 144/3^2 = 144/9 = 16 relative units. Photosynthesis rate need not follow if another factor limits it.
Check the conclusion and its limits
- Inverse square applies to light intensity in the stated model, not automatically to photosynthesis rate across all conditions.
- A plateau can reflect another limiting factor.
- Profit uses both income and cost; comparing income alone is insufficient.
Not true: Maximum photosynthesis rate must always give maximum profit. Profit = revenue minus costs. A change that lifts photosynthesis can cost more than the extra revenue it brings - the worked case shows a photosynthesis gain reducing profit by 30 units.
- Photosynthesis factors interact: light, carbon dioxide or temperature can limit rate under a particular set of conditions.
- For the ideal point-source model, light intensity is proportional to 1/distance².
- Watch for: inverse square applies to light intensity in the stated model, not automatically to photosynthesis rate across all conditions.
Profit = revenue minus costs.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. Profit = revenue minus costs. A change that lifts photosynthesis can cost more than the extra revenue it brings - the worked case shows a photosynthesis gain reducing profit by 30 units.
A condition whose shortage restricts the process rate: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
limiting factor means A condition whose shortage restricts the process rate.