The graph shows the results of a classroom investigation into the factors affecting the rate of photosynthesis - Leaving Cert Biology - Question 14(a) - 2011
Question 14(a)
The graph shows the results of a classroom investigation into the factors affecting the rate of photosynthesis. The variable investigated was either light intensity ... show full transcript
Worked Solution & Example Answer:The graph shows the results of a classroom investigation into the factors affecting the rate of photosynthesis - Leaving Cert Biology - Question 14(a) - 2011
Step 1
Suggest a suitable plant for such an investigation.
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Answer
A suitable plant for this investigation is an aquatic plant such as Elodea.
Step 2
How was the rate of photosynthesis measured?
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The rate of photosynthesis can be measured by counting the number of bubbles produced per unit time or by using a datalogging sensor to measure the volume of oxygen produced.
Step 3
Name a factor that must be kept constant during this investigation.
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Answer
A factor that must be kept constant is the light intensity if light is being investigated; if CO₂ concentration is the focus, then temperature must be kept constant.
Step 4
Explain how you would keep constant the factor referred to in (iii).
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To keep light intensity constant, a fixed lamp distance or wattage should be used, ensuring that the light source's intensity remains uniform throughout the experiment.
Step 5
Why is it necessary to keep that factor constant?
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It is necessary to keep that factor constant to ensure that any changes observed in the rate of photosynthesis are solely due to the variable being tested, and not influenced by fluctuations in light intensity or other external factors.
Step 6
What happens to the rate of photosynthesis at X when the investigation is
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A. carried out at 25°C? The rate of photosynthesis increases or does not level off.
B. carried out at 35°C? The rate of photosynthesis may not increase any further or levels off.
Step 7
Give a reason for each answer.
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A. At 25°C, the optimal conditions for photosynthesis may still be met, allowing for increased rates.
B. At 35°C, the temperature could either limit the rate of photosynthesis or it could lead to a denaturation of enzymes involved, preventing further increases.
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