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# Investigate the effect of light intensity on the rate of photosynthesis

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Introduction

Planning Title: Investigate the effect of light intensity on the rate of photosynthesis. The aim of my investigation: To find out how does the amount of light effect the amount of photosynthesis. The variables that affect photosynthesis are: * Light intensity * Carbon dioxide * Water * Temperature * Chlorophyll (the size and the shape of the leaves) The only factor I will change is light intensity because I want to investigate the effect of light on the amount of photosynthesis so if I want to get a correct result I should keep the other variables constant and just vary the light. To make sure my investigation is safe I took care not to touch the hot lamp. I also made sure that the lamp did not touch the water. Photosynthesis is the process that allows green plants to produce their own food. For this process to occur energy is needed in the form of sunlight. Chlorophyll absorbs the sunlight and is found in the chloroplasts of green plants. The light energy is used to convert Carbon Dioxide and water into sugars. The sugars are the plant's food and oxygen is the waste products. Photosynthesis takes place in a number of stages but this is the equation for the whole process: Carbon dioxide + water sugar + oxygen 6CO + 6H O ...read more.

Middle

The results show that the amount of oxygen bubbles produced goes down in direct relation to reduction in the light intensity. The line on the graph declines steadily. When the weed was 5cm, away from the lamp there were 78 bubbles produced in 1 minute. When the weed was 10cm away from the lamp there were 74 bubbles produced in 1 minute. At a distance of 15cm, 56 bubbles were produced in 1 minute. At 20cm, 43 bubbles were produced in 1 minute. At a distance 25cm, 28 bubbles were produced in 1 minute. When the weed was 50cm, away from the lamp 11 bubbles were produced in 1 minute. At a distance 100cm, 5 bubbles were produced. These patterns and results can be explained from my understanding knowledge that light intensity affects the amount of food or sugar which can be produced by a plant. These conclusions were the ones that I had predicted in my plan. I had said, in my plan that the higher the light intensity the greater the rate of photosynthesis. My results show that my prediction was correct. My results match the predictions because I made sure that I carried out a fair test. I only changed the variables I was investigating (light). ...read more.

Conclusion

Evaluation: My investigation was fair because I used the same tree in the same time of year and the same quadrates. I placed the pen in the same position. Also there was only one tree in the place I was doing my experiment in. It was accurate because I took two readings for each distance then calculated the average On the graph you can notice some anomalous points circled. This is because either: * Human error * the measurements were not accurate * I did not check the squares properly (to see if there is coverage of grass or not) If I do this experiment again I will take more readings. My prediction was "There will be more growth of grass further away from the tree than nearer the tree". There is more sunlight away from the tree which makes photosynthesis occur quicker. The tree branches and leaves prevent a lot of sunlight to go to the grass which makes the process slower. The more you add a catalyst the quicker the reaction will be. The sunlight and the chlorophyll are the catalysts in this process. So the more the sunlight the quicker photosynthesis occurs. This supports my prediction. Photosynthesis can be carried in further experiments for example Light reaction, dark reaction or artificial photosynthesis. ...read more.

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