lesson
The limiting factor can change
1 · Learn
Photosynthesis uses light energy to make organic material from carbon dioxide and water. Its rate can be limited by light, carbon dioxide, temperature or other conditions. Increasing a factor no longer helps once another factor limits the rate.
A plateau on a graph does not mean the process has stopped. It can mean the measured rate has stopped increasing under those conditions.
2 · Worked example
If increasing light initially increases rate but later gives a plateau, another factor may have become limiting. The graph alone may not identify which one.
3 · Your turn
Does a non-zero plateau mean photosynthesis has stopped?
Check your answer
No. It means the measured rate remains approximately constant rather than increasing further.
4 · Apply your learning
Use a supplied graph to identify where an increase has an effect and propose a controlled follow-up comparison.
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Use supplied data and approved diagrams. Laboratory work requires qualified supervision, suitable equipment and a risk assessment. No independent chemical, electrical, heating, radiation or biological-culture experiments. Human biology is general education, not personal diagnosis or treatment.
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Check a calculation · Year 5 onward
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Powers, roots and trigonometry · Year 7 onward
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