Photosynthesis
This practical lesson covers:
- How to investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism, pondweed.
Aim:
To investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed.
Background information:
Photosynthesis is the process by which plants, algae, and some bacteria transform carbon dioxide and water into glucose and oxygen, in the presence of light. In this practical, you will use pondweed to study how varying light intensity affects the rate of photosynthesis, observable through the production of oxygen bubbles. By adjusting the distance between the pondweed and a light source, you will directly measure the impact of light intensity on photosynthesis.
Variables:
- Independent variable - the light intensity (how close the light is).
- Dependent variable - the number of oxygen bubbles given off (the rate of photosynthesis).
- Control variables - the size of the pondweed, the volume of water used and the temperature of the water.
What is the role of the measuring cylinder in the experiment?
to measure the temperature of the water
to measure the volume of gas produced by the pondweed
to measure the distance between the pondweed and the light source
to measure the time taken for the experiment
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What is the dependent variable in the experiment?
number of bubbles released by the pondweed
volume of water in the measuring cylinder
light intensity
distance between the pondweed and the light source
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What is the purpose of repeating the experiment at different distances?
to investigate the effect of carbon dioxide concentration on the rate of photosynthesis
to investigate the effect of temperature on the rate of photosynthesis
to investigate the effect of light intensity on the rate of photosynthesis
to investigate the effect of surface area on the rate of photosynthesis
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What is the independent variable in the experiment?
light intensity
distance between the pondweed and the light source
number of bubbles released by the pondweed
volume of water in the measuring cylinder
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