Photosynthesis Investigation.

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Photosynthesis Investigation

Analysis

                  Below is the data table showing my results from the investigation, I have also added an adjoining column and calculated the mean average (total of items  number of items) of the five trials at each level of light intensity:

I believe that there are a few anomalous results in the above table and I have decided not to include them in my experiment as I believe they are inaccurate and might distort my conclusion.  In the table below I have highlighted any anomalous data that I will remove.  I have also drawn a graph of the averages, calculated above, to assist me in identifying inaccurate data.  

   Any anomalous data I successfully identified, by studying the table of results and by observing irregularities in the trend of my averages on the graph, has been omitted and not included in calculating my new averages.

   I have decided to plot the light intensity (%) against the volume of the gas (mainly oxygen) bubble produced per 10mins per 10g of Elodea (mm³).  In order to work out the volume of the gas bubble I will use the formula:

V = π r² x l

V = volume of gas (mainly oxygen) bubble (mm³)

r = the radius of the capillary tube, 0.5mm

l = the length of the bubble (mm)

Below is a table containing the new, more accurate averages of the gas bubble length and the gas bubble volumes.

Graph (see attached sheet)

   From the graph you can see that I have drawn my line of best fit through the origin (0,0).  I have done this deliberately because I already know that without light energy, a plant cannot photosynthesise.  “Photosynthesis takes place in the chloroplasts… tiny, membrane-bound bodies containing millions of molecules of the green, light-trapping pigment chlorophyll. The chlorophyll traps energy from…[the] light and transforms it into chemical energy…[and] oxygen is released…” (Dorling Kindersley Encyclopedia of Science – ©1997).  This suggests that the graph does not steadily increase before reaching a plateau but actually curves.  

   As I predicted, my graph shows that as the light intensity is increased so does the rate of photosynthesis, proved by the increase in the rate of the gas bubble volume.  I can closely follow the progress of the chemical reaction by observing how the products appear.  The increase in the rate of oxygen production strongly implies that the rate at which photosynthesis occurs is also increased.  I believe that if the light falling on each part of the leaf is more intense, then more energy is being provided for the reaction, and subsequently the rate at which it takes place is also increased.  

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   I also predicted that as the light intensity doubled, the rate of photosynthesis would also double, as there would be twice as much energy available to drive the reaction.  There would also be twice as many carbon dioxide molecules reacting with water molecules, forming twice as many glucose molecules and producing twice as many oxygen molecules, in the given time limit.  I predicted that my graph would clearly show that the rate of photosynthesis is directly proportional to the light intensity, by a positive correlation.  Although there two are interrelated they are not directly proportional to each other, as ...

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