Photosynthesis and limiting factors
| English | Français |
|---|---|
| photosynthesis/ˌfəʊtəʊˈsɪnθəsɪs/ | photosynthèse |
| limiting factor/ˈlɪmɪtɪŋ ˈfæktə/ | facteur limitant |
What would explain this observation?
- A brighter lamp does not always produce more oxygen from pondweed. Another factor may limit the process when light is already sufficient.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Photosynthesis · Photosynthèse 光合作用 transfers energy from light into chemical stores. Carbon dioxide and water form carbohydrate, releasing oxygen. Chlorophyll absorbs light; light intensity, temperature and carbon dioxide supply can affect rate.
- limiting factor 限制因素: A factor whose shortage restricts rate; photosynthesis: Light-driven formation of carbohydrate.
A rate-light graph reaches a plateau. What follows?
Change only one factor when testing a limiting factor. At low light, extra light may increase rate. At a plateau, the changed factor is no longer the main limit in that range; the graph alone does not identify which other factor is limiting.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Change only one factor when testing a limiting factor. At low light, extra light may increase rate. At a plateau, the changed factor is no longer the main limit in that range; the graph alone does not identify which other factor is limiting.
- Measure collected gas volume over a fixed time instead of assuming all bubbles have the same volume. Control temperature, plant size and carbon dioxide supply. Allow the plant to adjust before each reading and repeat.
Which two habits make the investigation or model in this case more defensible?
Measure collected gas volume over a fixed time instead of assuming all bubbles have the same volume. Control temperature, plant size and carbon dioxide supply. Allow the plant to adjust before each reading and repeat.
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: 6.0 cubic centimetres of gas are collected in 3.0 minutes. Use rate = volume/time. Rate = 6.0/3.0 = 2.0 cubic centimetres per minute. Bubble counts can be a rough proxy, but bubbles of different size make comparisons less reliable.
9.0 cubic centimetres of gas are collected in 3.0 minutes. Find the rate. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
9.0 cubic centimetres of gas are collected in 3.0 minutes. Find the rate.
The result is 3 cm³/min. Known: 6.0 cubic centimetres of gas are collected in 3.0 minutes. Use rate = volume/time. Rate = 6.0/3.0 = 2.0 cubic centimetres per minute. Bubble counts can be a rough proxy, but bubbles of different size make comparisons less reliable.
Check the conclusion and its limits
- Moving a lamp changes light and may also change temperature. A photosynthesis experiment needs control of heating, not just a ruler.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
All oxygen bubbles have exactly the same volume. This claim is false: Moving a lamp changes light and may also change temperature. A photosynthesis experiment needs control of heating, not just a ruler.
Photosynthesis and limiting factors: Change only one factor when testing a limiting factor. At low light, extra light may increase rate. At a plateau, the changed factor is no longer the main limit in that range; the graph alone does not identify which other factor is limiting.
All oxygen bubbles have exactly the same volume.
Moving a lamp changes light and may also change temperature. A photosynthesis experiment needs control of heating, not just a ruler.
A factor whose shortage restricts rate: write the technical term.
limiting factor means A factor whose shortage restricts rate.