• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Light Intensity and Photosynthesis.

Extracts from this document...

Introduction

Light Intensity and Photosynthesis Biology Coursework Aim The aim of my experiment was to determine whether or not the intensity of light would affect the rate of photosynthesis in a plant. To do this, I placed a piece of Canadian pondweed in varying light intensities, and observed the amount of oxygen being given off. I used Canadian pondweed because of its unusual quality of giving off bubbles of gas from a cut end, when placed in water. Introduction Photosynthesis occurs only in the presence of light, and takes place in the chloroplasts of green plant cells. Photosynthesis can be defined as the production of simple sugars from carbon dioxide and water causing the release of sugar and oxygen. The chemical equation for photosynthesis can be expressed as: (light) 6CO2 + 6H2O � C6H12O6 + 6O2 (in the presence of chlorophyll) The fact that all plants need light in order to photosynthesise has been proven many times in experiments, and so it is possible to say that without light, the plant would die. The reason that light intensity does affect the rate of photosynthesis is because as light, and therefore energy, falls on the chloroplasts in a leaf, it is trapped by the chlorophyll, which then makes the energy available for chemical reactions in the plant. Thus, as the amount of sunlight, or in this case light from a bulb, falls on the plant, more energy is absorbed, so more energy is available for the chemical reactions, and so more photosynthesis takes place in a given time. There are many factors, which affect the rate of photosynthesis, including light intensity, temperature and carbon dioxide concentration. The maximum rate of photosynthesis will be constrained by a limiting factor. ...read more.

Middle

The light intensity was measured in the same way as described in the preliminary experiment, and assumed to be the same at any point at any particular distance. When bubbles are being produced at a steady rate, clear any previous bubbles from the tubing by moving the syringe. Start the stopwatch, and wait for 1 minute. Move the bubbles, which have been collected at the bend in the tubing to the part of the tube with a scale. Find the length of the bubble collected. Repeat for all other readings, and then repeat all readings a second time to get an average result for each distance. Audus apparatus Using the described method, I found the following results: Results for main experiment Distance Light intensity length 1 length 2 average length (cm) (lux) (mm) (mm) (mm) 5 1015 3.5 3.5 3.5 10 945 3.5 3.5 3.5 12 770 4 3 3.5 14 639 3.5 3.5 3.5 16 500 3 3.5 3.25 18 395 3 3 3 20 310 2 3.5 2.75 25 208 1.5 2.5 1.75 30 149 1.5 1.5 1.5 35 110 1 1 1 40 80 0.5 1 0.75 45 55 0 0.5 0.25 Although, because I was using light intensity as my variable, I did not need to record the distances as well, I did, simply to use them as a marker for each result, so that I only had to record the light intensity once at the beginning and from then I just had to align the lamp at the correct distance each time. Analysis My graph was in the form of a best-fit curve. I drew it as a curve rather than a straight line because of the clear pattern of the points. ...read more.

Conclusion

Again if I were to carry out the experiment over a longer time period, it would have been necessary to add sodium hydrogen carbonate to the water to increase the carbon dioxide concentrations. The last inaccuracy, though a small one, was in the time keeping. The main problem here was in when to begin the minute. If for one reading, the minute was started just after one bubble had been produced, and in another reading it was just before, this could have had a negative effect on the accuracy of my results. I therefore ensured that in each case I started the stopwatch just after a bubble had been produced, thus heightening the accuracy. Overall, I felt that due to the small volumes of oxygen involved, my experiment was not as accurate as it could have been, however I believe it was accurate enough to support and justify my hypotheses. Improvements could have been made as I have stated, mainly by simply increasing the time taken. However, due to practical time constraints in taking the readings for my investigation, and some consequential problems relating to time extension, I could not in fact make these adjustments. The other obvious way of increasing the reliability of my results would be to take many repeat readings and find an average. To extend my enquiries into the rate of photosynthesis, I could perhaps try to link in some of the other limiting factors to the same experiment, as well as investigating them in their own right. It could also be interesting to explore the effects of coloured lights on the rate of photosynthesis, which could lead to the question of whether or not other types of light, such as fluorescent lights or halogen lights, would have a different effect on the rate of photosynthesis. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

4 star(s)

Overall, this is a very competent piece of work which investigates the effect of light intensity on the rate of photosynthesis. The writer has produced a concise and well-written account of the investigation with most aspects of a GCSE practical report covered in sufficient detail to gain the higher grades. Preliminary work was effectively used to establish the best method, and the results collected were analysed in some detail.

The report would benefit, however, from the following improvements:

[1] Reference in the introduction to previous work carried out by other students. There is a great deal of this online. This would have enabled the student to make detailed predictions.

[2] A risk assessment was missing and is now a vital part of every report.

[3] A more detailed quantitative analysis of the results was needed to enable the reader to fully understand the relationship between the IV and DV. Comparisons of the data collected here with that collected by other students would also prove useful in measuring the reliability of this work.

Overall, however, a good effort which, with small improvements, would have gained 5 stars.

4 stars.

Marked by teacher Ross Robertson 24/06/2013

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. Marked by a teacher

    Biology CourseworkTo determine if the distribution of flora across Ellerbeck is due to chance. ...

    5 star(s)

    Therefore an increase in soil temperature would affect enzymes involved in planet reactions such as Ribulose Biphosphate Carboxylase which catalyses the CO2 and the five-carbon sugar ribulose biphosphate in the Calvin cycle, in the dark reaction of photosynthesis. An increase in temperature would increase the rate of photosynthesis so increasing the growth rate of the plant.

  2. Marked by a teacher

    Investigating the rate of cooling water in a beaker.

    My prediction is based on Newton's law of cooling as the law states; the rate of change of the temperature of an object is proportional to the difference between its own temperature and the ambient temperature (i.e. the temperature of its surroundings).

  1. Peer reviewed

    An Investigation into the Effects that Different Light Intensities have on the Speed of ...

    5 star(s)

    I have chosen to use a projector light because if I was to use a bulb, the heat given off may affect the reliability of my investigation by raising the temperature at lower distances. I will measure light intensity using a light probe, which will be placed, in a fixed position at a fixed angle (using black tape)

  2. Experiment to investigate the effect of Carbon Dioxide on the Rate of Photosynthesis

    counter will be used to count the number of bubbles being released from the plant. 3. The amount of time the bubbles would be counted for was 2 minutes at first, but because there are so many bubbles being produced, the time will be reduced to 1 minute so the results are likely to be more accurate.

  1. Investigating the Factors Affecting Respiration in Yeast.

    2. The glucose solution and the air inside the syringe could have affected the rate and helped the enzymes work at higher temperatures. 3. There may have been a mistake made at the start of one of the warmer temperatures experiments.

  2. The effects of osmosis in plant tissues

    To ensure fair testing, only one variable should change at one time. Everything must be kept constant except for the solution concentration. This means that the temperature was kept constant and the areas and masses of the cucumber slices were tried to be kept as constant as possible.

  1. How does light intensity affect the rate of photosynthesis

    There are different factors that affect the rate of photosynthesis and these include factors directly involved in the photosynthesis reaction e.g. light, water, carbon dioxide etc, and also other things that limit how much photosynthesis takes place in the plant e.g.

  2. How Light Intensity Affects the Rate of Photosynthesis

    and end of the experiment so that the results are all fair. Next, I set up the lamp at the first distance and make sure it is at the correct distance from the pondweed and not from the edge of the beaker.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work