More Intense The Light example essay topic

Biology Coursework: Photosynthesis The aim of the experiment was to investigate a factor that would affect the rate of photosynthesis in a Canadian pondweed plant. Canadian pondweed is used because it has an unusual quality of giving off bubbles of oxygen from a cut end and it's easy to see and monitor / count the bubbles in water. It was decided to use light intensity as the experimental variable, different paper will be wrapped around the beaker containing the pondweed and different amounts of light will be let in. The following will be kept as fixed variables: Carbon Dioxide- the more CO 2 there is in the air the more there is that can diffuse into the leaf. This is kept the same by adding a spoonful of sodium hydrogen carbonate to the beaker containing the plant. ' Temperature- plants contain enzymes, which denature at unreliable temperatures, so by increasing the temperature the enzymes activity will increase; this will be kept the same by being done in normal air, within a short time period and in the same place.

D Water- water is connected to the CO 2 factor, because if there is a lack of water in a plant, the stomata close to stop any more water loss, this also prevents CO 2 from diffusing into the leaf. ' Plant- different types of plants photosynthesis at different rates because of the different leaf shapes and structures; the surface area also affects, a bigger surface area means more space available for gas exchange. The only way to keep all this frequent throughout the experiment will be to use the same plant for the whole experiment. Light wavelength (colour) - leaves, containing chlorophyll, are green causing them to reflect green and yellow light rather than absorbing them, blue and red light is easily absorbed; the different lights cause different amounts of energy to be absorbed by the plant and this consequently has an effect on the rate of photosynthesis.

This will be kept the same by the beaker being put in one sunny spot and left there throughout the whole experiment. There are also some limiting factors: light, carbon dioxide chlorophyll and temperature are all affecting, when there is a surplus of all the other variables, the rate of photosynthesis will be constrained by these, until they are at their most advantageous level and the rate will peak. The experiment is to prove that the more intense the light, the faster the rate of photosynthesis (number of bubbles per minute) will be. This is thought, because photosynthesis only happens when there is light, water and carbon dioxide and if a plant is deprived of any of these the rate of photosynthesis drops, so if one is made more intense it should increase. The equipment used will be: a piece of Canadian pondweed, water, a beaker, black and greaseproof paper, a stopwatch a boiling tube and a funnel. Four different light intensity's were to be applied to the plant, after the apparatus had been set up as in the diagram below.

The four different light intensities are to be produced by leaving the plant in a normal sunny position for normal light, a spotlight shining on it and silver foil wrapped around it for intense light, greaseproof paper wrapped around it for partial light and black paper wrapped around it for no light. The stopwatch will be used to time exactly a minute and the number of bubbles given off by the plant will be recorded. The Results: Minutes No Light Partial Light Normal Light Intense Light 1 10 0 30 3 2 4 0 30 3 3 4 0 28 3 4 7 0 35 5 5 3 0 38 3 Average 5.6 0 32.2 3.4 These results are remarkable and very unexpected. They disprove the hypothesis, but there are many possible reasons for these strange results: maybe the plant was unsettled, maybe there is a particular problem with light getting through greaseproof paper or the temperature of the water may have changed.

To find out if this was an anomaly the experiment will be redone and its results analysed. Minutes No Light Partial Light Normal Light Intense Light 1 18 8 20 19 2 10 4 22 21 3 9 12 19 7 4 11 4 14 8 5 12 9 29 11 Average 12 7.4 20.8 13.2 These results conform much more with expectations and are much more likely to be true than the previous set. These results disprove the hypothesis, because they show that Normal / Natural Light makes the plant produce the fastest rate of photosynthesis. This could be because the light is actually the sun's rather than artificial light. This outcome is much more compact than the varied results of the previous experiment. There were several possible errors in this experiment.

One was that it was possible for the number of bubbles to be miscounted, another was that the temperature could have been changing, yet that could not be perfectly controlled. Overall, this experiment had good results (in the end) but still could be improved upon.