Part 1: Answers to Preliminary Questions
• Photosynthesis is the process by which green plants use sunlight energy to manufacture food using water and carbon dioxide as raw materials.
• An increase in the intensity of sunlight increases the rate of photosynthesis up to a given level.
• Photosynthesis and respiration processes complement each other. It is possible to examine the relationship between photosynthesis and cellular respiration under controlled experimental conditions. This can be conducted by setting up an experiment with two sets of experimental set-ups. In each set-up, there should be two test-tubes: one with a high concentration of carbon dioxide and another with a high concentration of oxygen. One pair of test tubes, consisting of a test-tube with a high concentration of oxygen, and another one with a high concentration of carbon dioxide, should be placed in the dark while another pair should be placed in the sun. It is expected that the photosynthesis will occur in tubes placed in locations where sunlight is accessible while only respiration will occur in tubes placed in the dark. Bromothymol blue should be added to all the tubes to indicate the changes in oxygen and carbon dioxide concentration.
Part 2: Lab Report
Purpose
This experiment was intended to investigate the effect of the intensity of light on the rate of photosynthesis.
Introduction
Photosynthesis refers to the process by which green plants manufacture food from water and carbon dioxide using the energy of sunlight (Demirbas, 2010, p. 34). Factors that affect the rate of photosynthesis include light, carbon dioxide level, and temperature. Other factors that affect photosynthesis include water and concentration of chlorophyll. Light intensity only affects the rate of photosynthesis to some extent. As the light intensity increases, the rate of photosynthesis increases up to a given level beyond which changes in the light intensity do not affect the rate of photosynthesis. Concerning the effect of carbon dioxide on the rate of photosynthesis, an increase in the carbon dioxide concentration results in an increase in the rate of photosynthesis and vice versa (Whitton, 2012). However, the effect of the level of carbon dioxide on the rate of photosynthesis is limited to specific levels.
Hypothesis
The hypotheses tested in the experiment are as follows:
• H1: If light intensity is increased, the number of bubbles originating from the seaweed per hour will increase
• H0: If light intensity is increased, the number of bubbles originating from the seaweed per hour will not increase
Methods
The experiment was conducted by measuring the number of bubbles arising from seaweed placed in water under various intensities of light. The set up in the experiment was prepared by filling a beaker with water and submerging the seaweed in the water. The set-up was then placed under different condition of light intensity by illuminating it with light from different light bulbs of different intensities.
Results
The number of bubbles in each trial is shown in Table 1 below:
Discussion and Analysis
The results show that an increase in the intensity if sunlight causes an increase in the rate of photosynthesis. Consequently, the hypothesis, which states that if the light intensity is increased, the number of bubbles originating from the seaweed per hour will increase, is accepted. On the other hand, the null hypothesis, which states that if the light intensity is increased, the number of bubbles emerging from the seaweed per hour will not increase, is rejected. The bubbles originating from the seaweed are oxygen released as the by-products of the photosynthesis process. The experiment was successfully conducted since all the objectives of the experiment were met. However, errors were reported. One of the possible sources of error in the experiment could be variation in the room temperature. This experiment concludes that light intensity affects the rate of photosynthesis in that an increase in light intensity leads to an increase in the rate of photosynthesis.
References
Demirbas, A. (2010). Biorefineries: For biomass upgrading facilities. Dordrecht: Springer.Top of Form
Whitton, B. A. (2012). Ecology of cyanobacteria II: Their diversity in space and time. Dordrecht: Springer.
