Also, from doing preliminary work, we created a new, more efficient way to stabilize the angle of the light. Elastic bands are put around the light neck of the light so that it will stay secure. This method will save a lot of superfluous movement.
From doing the preliminary work, I also decided that two people should count the oxygen bubbles released mutually so that the least amount of bubbles is missed. It was tough to decide which bubbles we would count, as there are various types of bubbles from large to small. To make it fair, we decided to count only the ones that reach the criteria; carry a higher volume of oxygen and very noticeable. These and only these will be counted. In all probability, at a cut end of the elodea is where the bubbles will be much larger. When the oxygen bubbles are released from the stomata, they are much smaller but there is a longer strand. From the cut, there is more space for a bigger oxygen bubble to be released.
The intensity of the light should stay constant throughout the experiment. This also applies to the temperature. We know that the light we are providing exclusively for the experiment is not all that will be added to the light reaching the plant. The lights for the room and also the light from the sun will add to the light the elodea will be receiving.
Here are results that were found when my group performed a small test counting the amount of bubbles in the duration of five minutes:
* The distance is always measured from the edge of the boiling tube to the edge of the lamp.
* The temperature should not go any higher than 22 degrees Celsius so that the enzymes will not be denatured.
Scientific Knowledge:
Sunlight plays a much larger role in our sustenance than we may expect: all the food we eat and all the fossil fuel we use is a product of photosynthesis, which is the process that converts energy in sunlight to chemical forms of energy that can be used by biological systems. Photosynthesis is carried out by many different organisms, ranging from plants to bacteria. The best-known form of photosynthesis is the one carried out by higher plants and algae, as well as by cyanobacteria and their relatives, which are responsible for a major part of photosynthesis in oceans. All these organisms convert CO2 (carbon dioxide) to organic material by reducing this gas to carbohydrates in a rather complex set of reactions. Electrons for this reduction reaction ultimately come from water, which is then converted to oxygen and protons. Energy for this process is provided by light, which is absorbed by pigments (primarily chlorophylls and carotenoids). Chlorophylls absorb blue and red light and carotenoids absorb blue-green light, but green and yellow light are not effectively absorbed by photosynthetic pigments in plants; therefore, light of these colors is either reflected by leaves or passes through the leaves. This is why plants are green.
Photosynthesis takes place primarily in plant leaves, and little to none occurs in stems, etc. The parts of a typical leaf include the upper and lower , the , the vascular bundle(s) (veins), and the . The upper and lower epidermal cells do not have chloroplasts, thus photosynthesis does not occur there. They serve primarily as protection for the rest of the leaf. The stomata’s are holes, which occur primarily in the lower epidermis and are for air exchange: they let CO2 in and O2 out. The vascular bundles or veins in a leaf are part of the plant's transportation system, moving water and nutrients around the plant as needed. The mesophyll cells have chloroplasts and this is where photosynthesis occurs.
As you hopefully recall, the parts of a chloroplast include the outer and inner membranes, intermembrane space, stoma and thylakoids stacked in . The chlorophyll is built into the membranes of the thylakoids.
Chlorophyll looks green because it absorbs red and blue light, making these colours unavailable to be seen by our eyes. It is the green light, which is NOT absorbed that finally reaches our eyes, making chlorophyll appear green. However, it is the energy from the red and blue light that are absorbed that is, thereby, able to be used to do photosynthesis. The green light we can see is not/cannot be absorbed by the plant, and thus cannot be used to do photosynthesis.
The overall chemical reaction involved in photosynthesis is: 6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2. This is the source of the O2 we breathe, and thus, a significant factor in the concerns about deforestation.
An animated picture of the process of photosynthesis, which shows very clearly what, happens during this process.
This picture shows the raw materials are significant and what the outcomes are.
The process of photosynthesis releases oxygen into the atmosphere and by using the carbon dioxide. The oxygen is very much in demand by the animals and humans especially. We use oxygen in the process of respiration. In addition, all animals depend on plants for a source of food because all the major diet components are synthesized inside the plant. Some of the light energy is stored by the chlorophyll and converted into chemical energy, stored in the molecular structure of the sugars in the plants.
This law applies to my experiment because as I move the light further back, the energy that is provided expands further out and does not focus as much on the pondweed.
Relationship of scientific knowledge to experiment:
The scientific knowledge that I have obtained or already studied will exceedingly help me during my experiment and the write up of this coursework. From knowing the inverse square law, I can make an accurate prediction as to what will occur when the distance of the light to the pondweed increases. As less light energy is reaching the pondweed itself, the rate of photosynthesis will unquestionably become slower.
It is significant that you try and hold a stable and well-formed environment for the pondweed. By this I am implying that the three main factors (temperature, light, carbon dioxide) have to be provided at a constant level. Therefore, the pondweed will not have a shortage of anything.
The plants stoma does not have nearly the same amount room to release large oxygen bubbles. Consequently, the bubbles released are small and imperceptible. Knowing this, I will recognize where t look for the larger oxygen bubbles; at a cut end.
Apparatus: Beaker, boiling tube, detergent, elodea crispa, lead strip, Plastocene/ blu-tack, “pond” water, sodium hydrogencarbonate, spatula, thermometer, water bath- to act as heat shield.
Method: The method for any experiment is essential. It has to be conventional, accurate, and also safe. The method that my colleagues and I came up with seems to match the criteria mentioned. The first step is to collect all of the apparatus needed and as I mentioned earlier, I have chosen to count the amount oxygen bubbles released. When all of the equipment was collected, as a group, we set up the experiment in relation to what we wanted. We made sure that the amount of space we had to work in was enough and used up appropriately.
You first need to take the blu-tack and stick it to the bottom of the boiling tube. Than, you take the boiling tube and fill it with the necessary water. Make sure this is “pond” water. When you have done this, you take the lead strip and securely wrap it around the top of the elodea. Next, place the pondweed into the boiling tube.
Next, you take the large beaker and fill it with water. This beaker should have enough water so that when the boiling tube is placed inside it (normally 200cm cubed, the water of the beakers water can act as a heat shield to the whole of the pondweed. The elodea should have a small cut for it to be able to release large oxygen bubbles.
When you have filled the beaker with the substantial amount of water, you take the boiling tube and place it carefully inside the beaker. Make certain that the blu-tack is firmly stuck to the bottom of the beaker and will not fall over.
For the next step, you take the detergent and add no more that 4 drops of it to the boiling tube. Also, add one spatula-full of sodium hydrogencarbonate to the beaker. Now take the thermometer and place it into the beaker. Leave it in there for 30 seconds and check the temperature. Make sure that the temperature is not higher than 22 degrees Celsius and not dramatically lower.
Now that I have covered the setting up of the experiment, I will write about the doing of the experiment itself. This part of the method is modified to exactly how my colleagues and I executed the experiment.
From the preliminary work that my group and I had carried out, we had decided on exactly how long we will time for and which distance intervals we will use. For this experiment, it was a three-minute timing and a 5cm distance interval.
To start the testing, we supplied ourselves with a ruler to measure the distances accurately. The first distance was 5cm and it had been decided to try three attempts for each distance. We knew the temperature was 19 degrees Celsius and would stay constant, but we also measured the light intensity, which was 30 lux and the length of the elodea was 10cm.
Each one of the group members had a certain job to do. One member timed the three minutes, one measured the distance from the edge of the boiling tube to the edge of the lamp. After the distance was confirmed to be correct, the timer gave us a signal to when exactly he was going to start the timing so that we could be ready to start counting the bubbles. This method was done over and over again until we had finished the experiment. Three attempts were done for each measurement so that I can have a set of very accurate results. For each measurement, I also calculated the rate of bubbles per minute.
Diagram:
Fair test and reliability of results: To have reliable results is very important in any type of investigation. It is essential that you do anything in your power to make sure that nothing alien occurs. By this I am implying factors which we could prevent quite easily if we take the necessary precautions e.g. make sure the distance between the lamp and the boiling tube is exactly correct and make sure that you count the same type of bubbles for each attempt you are doing so that the results will be based on what you want them to be. Also, in my investigation, it was important for me to write down results that were obtained from the actual experiment rather than writing down results which did not happen but should have and sound more correct. This is all part of the process of learning by making mistakes.
This experiment was for the most part a fair test. With the satisfactory equipment provided and the class environment in which we had to perform the experiment, it is very difficult to get 100% accurate results. However, I am not trying to say the results were elusive, just not perfect. They were results my group and I obtained from making sure everything was happening correctly e.g. the timer and the person counting the bubbles start mutually and stop mutually for this matter, the angle of the light shining towards the elodea will always maintain the same.
Also, we took in hand some of the things that we could not change, e.g. the lights in the room, light from the sun, light reach us from other equipment. To make sure that everything was counted for, when measuring the light intensity, we included all of the light sources.
Safety: You should be aware of what accidents can occur with the apparatus you are using. I am using a quite powerful lamp and I should never look directly at it. Also, since the boiling tube and the beaker are both made out of glass, make certain you place them carefully or handle them with care. There is a possibility of that glass easily breaking and you can get a cut. These can be avoided just by concentrating.
Prediction: From the research that I have done and from the further discussions that I have had, I am going to make a well-planned prediction for this investigation. I predict that the further away the light is from the elodea plant, the less production of oxygen bubbles will be made. This is because less light is reaching the plant and, as light is one of the most important factors in photosynthesis, it would slow this process down if not enough light is reached. I am certain that the amount of light reaching the elodea plant will decrease because I know and am aware of the inverse square law which states if you double the distance between the light and the plant, the light intensity received by the plant is reduced by a quarter, and so on.
Results: These results have been obtained in the duration of my experimentation:
- Three minutes of timing each attempt
- The temperature was 19 degrees Celsius throughout the experiment
- The length of elodea is 10 cm
- The light intensity is 30 lux (all light counted for)
What I have found out: I have found out that the higher the light intensity is on the pondweed, the higher rate of photosynthesis.
Analyzing results and prediction: As you can see the table, it shows that my prediction was in fact correct and quite accurate. When you look at the table you can see it is quite stable as far a results are concerned. The amount of bubbles created by the process of photosynthesis decrease at a steady level and you do not see a big jump in the results, which shows that the procedures and steps taken throughout the experiment were not changed.
I was disappointed with the rate of oxygen bubbles that were created. I am not certain why there was not a fast, and long strand of bubbles, perhaps because it was from a cut rather than a stoma. Also, the bubbles per minute are shows that the creation of oxygen bubbles was steady for each minute. To stop timing at the distance 30 cm was the right decision to make because as you look at the table you can see that the rate of oxygen bubbles being created at 30 cm was decreasing very low and to go into 35 cm would not prove anything. If the stable decreasing of the bubbles followed through to the 35cm distance, we would have not more than 2 to 4 bubbles.
Conclusion:
In conclusion, the higher the light intensity onto the swig of pondweed, the higher the rate of photosynthesis. Not only do the sources that I have obtained agree with me e.g. scientific knowledge however, so do the results of a fellow colleague that I received through e-mail. The following results are from Sam Reynolds. He also did the same experiment as I.
The results in this table are very similar to mine and I will use them as a secondary source for results. It is evident that my results show a correlation in terms of accuracy.
Relations between my conclusion and my prediction: Ultimately, my results turned out in relations to what I had predicted. This is very satisfying to know because it proves that your work was efficient, and effective.
However, I also predicted said that as the lamp distance doubles the rate of photosynthesis is reduced by a quarter. Unfortunately this did not happen. In the experiment, as I doubled the distance, the rate of photosynthesis halved. I was not thinking about the limiting factors like I should have. By the limiting factors, I mean the level of carbon dioxide and the temperature. This very much affects the rate of photosynthesis and I believe to be the reason of my results not corresponding to the inverse square law.
Accuracy
I am very happy with the accuracy of my results. There were no results that seemed extremely wrong. I do think that the preliminary work helped me significantly with the outcome of my experiment. It helped me decide how long I would be timing for and which distance interval to use.
As I had mentioned earlier, it was the right decision to stop measuring at 30cm. I will not write why this is again because it is unnecessary.
Reliable Evidence
The evidence that I have purposed in this experiment are in fact very reliable. The scientific knowledge that I gathered together and the secondary results are both similar to the outcome of my results. Of course, my results are not 100% accurate thus, given the time, space, environment, and the satisfactory apparatus, this was the best I could do.
I am aware that I could have made a few improvements but other than that, the results were accurate.
Improvement and Further work
To make the rate of photosynthesis drop at a lower percentage, I could have used a smaller gap for the distance intervals. Instead of 5cm, I could have used 3. After doing the experiment, this seems to be a good choice because u could obtain results that are closer to each other.
There is always room for improvement in an experiment, and the following are a list of what I came up with:
- Every time the light is moved to a certain distance, there should be time given for the elodea to adjust to that source.
- Newer and more efficient apparatus that are made precisely for this experiment
- A room with a constant Temperature and level of carbon dioxide
- Find a new way of counting bubbles that is far more efficient. Counting with your eyes is not as accurate. I would come up with a new method of measuring the oxygen given off. This method can be different to what I have done for this experiment.