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One laboratory activity that you carried out demonstrated the influence of light intensity or of carbon dioxide concentration on the rate of photosynthesis - Leaving Cert Biology - Question c - 2009
Question c
One laboratory activity that you carried out demonstrated the influence of light intensity or of carbon dioxide concentration on the rate of photosynthesis. Answer t... show full transcript
Worked Solution & Example Answer:One laboratory activity that you carried out demonstrated the influence of light intensity or of carbon dioxide concentration on the rate of photosynthesis - Leaving Cert Biology - Question c - 2009
Step 1
Explain how you measured the rate of photosynthesis.
Answer
The rate of photosynthesis can be measured by counting the number of oxygen bubbles released by an aquatic plant, such as Elodea, over a specific period of time. Alternatively, the volume of oxygen produced can be measured using a gas syringe or a datalogging sensor to provide more accurate and consistent readings.
Step 2
Explain how you varied light intensity or carbon dioxide concentration.
Answer
Light intensity was varied by changing the distance of a light source from the plant. For example, moving a lamp closer or further away from the plant alters the amount of light energy reaching it, thus influencing the rate of photosynthesis. If carbon dioxide concentration was varied, it could be done by using different concentrations of sodium bicarbonate (NaHCO₃) solution in the water surrounding the plant.
Step 3
State how you kept another named factor constant.
Answer
The temperature was kept constant throughout the experiment by conducting the activity in a controlled environment, such as a water bath, ensuring that any changes in the rate of photosynthesis were due solely to variations in light intensity or carbon dioxide concentration.
Step 4
Draw a graph with labelled axes to show the results that you obtained.
Answer
The graph should display light intensity on the x-axis and the rate of photosynthesis (bubbles per minute or volume of oxygen produced) on the y-axis. Ensure that appropriate scales are used and each point on the graph accurately reflects the data collected.
Step 5
Briefly explain the trend in your graph.
Answer
The graph typically shows an increasing trend initially, indicating that as light intensity increases, the rate of photosynthesis also rises due to more available energy for the process. However, this trend may plateau at higher light intensities, suggesting that other factors, such as carbon dioxide or temperature, begin to limit the rate of photosynthesis.