Effects of temperature Essay Example for Free

Effects of temperature Essay Some of these are variables that were mentioned earlier and could not be controlled, or even variables that were not initially considered. While performing the experiment, some of the oxygen produced from photosynthesis may have dissolved into the water. Microorganisms living on the pondweed may have used some oxygen. Although the amount of oxygen dissolved or used by microbes may be insignificant to the final result, when considered alongside the other variables this factor may be attributed to a significant change in the results. Some oxygen is also used during the respiration of the plant. As only the volume of oxygen produced was recorded the change in bubble size was not accounted for when the results were analysed. For a more accurate analysis of the data, using a capillary tube in place of the test tube so that the size and volume of each bubble could have been measured would have eliminated this inaccuracy. There are also factors affecting accuracy at low light intensities. With low light intensity, the pondweed receives some light energy from background light such as sunlight seeping through curtains or the light from the lamp of another students experiment. To eliminate extra artificial light from interfering with the results, the experiment must be performed in a completely dark room. The methodology of the experiment is also likely to account for any errors made, so in order to improve reliability and validity of the results some methodological features must be improved upon or changed completely. A capillary tube and a syringe should be used in place of the test tube to accurately measure the volume of the oxygen produced. Due to the high rates of photosynthesis of the pondweed, readings should be taken within shorter time periods. Doing so decreases the likelihood of human error occurring. Due to the nature and convenience of the experiment, it could be easily modified to investigate other variables of photosynthesis. An experiment using almost identical apparatus would be to vary the colour of the light the plant absorbs. Using translucent colour filters in front the lamps could vary this. Whilst doing the experiment several times contributed to the accuracy of the experiment, there were factors that detracted from it. The method of measuring the rate of photosynthesis by the frequency of bubbles was one. The volume of the bubbles could have varied, meaning that a larger or smaller amount of oxygen could have been released without being recorded. To eliminate these errors, using apparatus like a micro-burette or some other tool for measuring small volumes of gas may overcome small inaccuracies. This would make the results more accurate and reliable. Modifications: Limitations. The room temperature may fluctuate. Â  The concentration of carbon dioxide in the water may be reduced during experiment. The rate of gas evolution is not consistent. Â  There are other light sources, which may interfere with the results. Artificial light will increase temperature, as a 60watt bulb will be used, some energy will be lost as heat energy. Â  Are the bubbles being observed actually oxygen? Setting up the apparatus and placing it in a water bath may overcome the first error. Doing so will ensure that a constant temperature is maintained throughout the experiment. To avoid other light sources interfering with the experiment shelter the apparatus up so that the pondweed only receives light from the table lamp. To ensure consistency of gas evolution when changing to a new condition, the plant should be equilibrated for at least 10 minutes before taking any readings. Using a dilute sodium hydrogen carbonate solution ensures a constant supply of carbon dioxide to the pondweed, avoiding fluctuation of carbon dioxide concentrations. To test for presence of oxygen simply lower a glowing splint into the test tube containing the gas; if the splint relights this indicates that oxygen is present. Using this test increases reliability of the results. The presence of the lamp may cause the temperature to increase; to prevent this from happening ice can be used to maintain a constant temperature. Further experiments could be implemented to test other factors that may have an affect on the rate of photosynthesis. Light intensity has been found to have an affect on photosynthesis. This can be investigated by placing a light at varying distances from the elodea plant and recording the number of bubbles produced. Other experiments in this area could also include testing the rate of photosynthesis with different amounts of chlorophyll in the plants. References: 1, 2, 3, 7 and 8 Glenn and Susan Toole, (1999) Biology for Advanced level. Stanley Thornes pg. 282-5. 4, 5 and 6 D. O. Hall and K. K. Rao, (1992) New studies in biology, Photosynthesis. Cambridge University Press, pg 13-14.