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Temperature and photosynthesis rate
A student investigated the relationship between temperature and the rate of photosynthesis. The student measured the volume of gas produced by an aquatic plant in 1 hour. The student collected the gas in a measuring cylinder. Table 2 shows the results.
| Temperature in °C | Volume of gas produced in 1 hour in cm³ |
|---|---|
| 10 | 1 |
| 15 | 2 |
| 20 | 4 |
| 25 | 8 |
| 30 | 16 |
| 35 | 16 |
| 40 | 2 |
| 45 | 0 |
Describe the effect of increasing temperature on the rate of photosynthesis. Use data from Table 2.
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Marking points
- 1 Describes the rate increasing and then decreasing as temperature rises.
- 2 Identifies the maximum/optimum as between 30 °C and 35 °C.
- 3 Uses the data to show that the rate doubles every 5 °C up to 30 °C, or describes the accelerating/exponential increase.
Full-mark answer
The rate increases as temperature rises up to about 30-35 °C, then decreases. From 10 °C to 30 °C the gas produced doubles every 5 °C, from 1 cm³ to 16 cm³ in 1 hour. The maximum rate is between 30 °C and 35 °C, after which it falls to 2 cm³ at 40 °C and 0 cm³ at 45 °C.
Why this answer loses marks
The gas volume increases and then decreases.
This describes the raw measurement but does not state the effect on photosynthesis rate or identify the supported optimum and changing pattern.