Biology Lab Report. Does light intensity affect the rate of photosynthesis?
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Title To investigate the effect of light intensity on the rate of photosynthesis Research question: Does light intensity affect the rate of photosynthesis? Hypothesis: Theoretically plants need light to undergo photosynthesis. At low light intensities, there is a shortage of the product of the light-dependent reactions. There fore if the light intensity is low, the rate of reaction will also be low. The hypothesis is that the rate of photosynthesis increases with the increasing light intensity and decrease with the decreasing light intensity. Variables: Independent : distance between the source of light and the pond weed Dependent : time taken for the color of sodium bicarbonate solution to turn from deep red to purple Constant : the apparatus settings, the volume of sodium bicarbonate Solution (5 cc), the length of pond weed (5 cm)
2 G 70 0 Data Processing Rate of photosynthesis can be calculated using formula as below: Number of bubbles released 20 minutes test tube distance from light source, cm rate of photosynthesis, no of bubble/ min A 10 4.5 B 20 1.9 C 30 1.1 D 40 0.8 E 50 0.3 F 60 0.1 G 70 0 Using the information from the table above, we can plot a graph of rate of photosynthesis against light. (see attachment) Conclusion The rate of photosynthesis is directly proportional to light intensity Evaluation: From doing this experiment, some flaws that have altered the experiments result has been detected. 1. The length of the pondweed is insufficient.
The amount of oxygen released will alternately increased therefore the experiments results will be much faster and the data can be taken in time 2. The time for doing the experiment should be increased so that there is enough time for the weed to released enough oxygen that will turn the indicator from deep red to purple. 3. The volume of the indicator should be decreased so that the colour changes of the indicator will be faster. The concentration of the indicator should also be reduced so that the colour changes would be faster due to the fact that the mole of the indicator is lesser than usual 4. The experiment should be done in a very dark place where there are no source of light because the present of other light source will alter the experiment's results
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The experimenter gave sufficient detail on how they would investigate the effect of light intensity on the rate of photosynthesis. How variables were to be controlled or manipulated was described, however, the need to control temperature was left out. It might also be important to identify safety issues that might be taken into consideration. Rating ****
Marked by teacher Agnes Mupandiraa 01/12/2012
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