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How light intensity affects the rate of photosynthesis
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How light intensity affects the rate of photosynthesis The aim of my experiment was to determine whether 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...
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.

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What feature do you expect to...What feature do you expect to find in most clover on a school field? Prediction: Variation is in people and all other living things, they vary in many ways. No two living things are exactly the same; even twins. Humans; for example, all have the same general shape and body organs, however characteristics such as height, weight, shape of face, knowledge, skills, body scars, etc"¦ differ from one person to the next. These characteristics are examples of variation. Variation is caused by sexual reproduction, when characteristics are inherited from each parent, e.g. colour of hair, eyes and skin. Mutations occur when there is a sudden change in a gene, or a chromosome, which alters the way in which it controls development. It can be caused by radiation"¦etc. It can be helpful by the characteristics they have gained could help them to survive in certain conditions. Survival of the fittest is also known as selection, where in the wild only the strongest survive. This is sometimes a good thing a good thing as if an animal is stronger and can run for longer and does survive, it will then reproduce other animals as strong as it that can also run for longer. Selection pressure is when something that happens over a long period of time, which tests the genes to see if it can survive. E.g. Famine and climate. Certain features are more common in a population because of succession and survival of the fittest. This is because of selection pressure, more and more species have the genes to survive when fewer and fewer have the genes to not stay alive- so to be killed. This is called succession. So the more genes which can survive, will be reproduced so in time, the whole population will be able to survive, so that certain feature will be more common. Here are the features that could help a clover plant to survive on a school field: v Long roots- to get more nutrients v Large surface area- to get more light v Tall stems- to get more light v Space- to have space to grow and get most nutrients v Not too much competition- so get enough space, nutrients, light and water v Thick roots- to get more nutrients v Thick stems- to get nutrients to parts of plant and storage v Rain- to get enough nutrients in the soil and for the plant to grow v Not too much long grass- so doesn't take up all of the light, space and nutrients v No pests- so don't eat leaves and plant v Where the grass cutter can't get to it- so doesn't cut down the plant. We would expect most surviving clover plants to exhibit these features because they all help the plant to survive; they give more nutrients to the plant. I am going to investigate this feature: Effect on stem lengths- Clover that get cut to have short stems, and clover which doesn't get cut to have long stems. I would expect the clover which does get cut to have short stems because the grass cutter would cut the tops of long stemmed clover, so to make the clover not get cut off and to live longer, the clover would have to adapt to the condition and have short stems. For the clover which doesn't get cut, I would expect the clover to have long stems because they have been left to grow and they will have to fight for competition as there would be other plants growing too and long grass; so for the clover to survive they would have long stems to get more light. Diagram We are going to test it by using a quadrat, to test the lengths of the clover in: v The long grass area with clover v The short grass area with clover We will measure 10 clover stems in each quadrat, we will use the quadrat twice for the cut grass with clover, and twice for the un-cut grass with clover. I will then find the average stem length for the un-cut and cut clover stems. Fair Test v Use the same quadrat v Measure using the same units with same ruler v Have same person measuring lengths v Randomly chucking the quadrat v Measuring same number of clover stems in each quadrat v Measure all on the same day v Measuring clover before the grass is cut so we can actually see the clover lengths v Only measuring alive clover, not dead.   

What feature do you expect to find in most clover on a school field? Prediction: Variation is in people and all other living things, they vary in many ways. No two living things are exactly the same; even twins. Humans; for example, all have the same...

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Aim to find out... Aim to find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose and water. Planning Apparatus 6 boiling tubes Sucrose solution Balance "“ 2dp for more accurate results Distilled water Razor blade Filter paper A potato Cork borer Method I labelled 6 boiling tubes as follows 1 "“ Distilled water 2 "“ 0.1 molar, sucrose solution 3 "“ 0.2 molar, sucrose solution 4 "“ 0.3 molar, sucrose solution 5 "“ 0.4 molar, sucrose solution 6 "“ 0.5 molar, sucrose solution I then filled the boiling tubes with a third of either the distilled water or sucrose solution. Using a cork borer I then took 6 cylinders of potato, 10-12mm long. I then sliced up each cylinder into 10 discs of equal size and thickness. I then put each group of 10 discs onto 6 separate pieces of filter paper and weighed them each then recorded their mass. I then placed each group of potato discs into each of the labelled boiling tubes. After 24 hours remove the discs and record their mass, I removed any excess surplus fluid by using filter paper. I then recorded the results of each of the boiling tubes again. Key factors to control The size of the potato discs The size of the potato discs must be kept the same because if there is a larger surface area, there are more cells, and diffusion will take place faster. Reversed, the smaller the surface area the fewer cells there are and therefore diffusion will take place slower to a place lower in concentration. The concentration of the solution The concentration of the solution is my independent variable. I am varying it from 0.1-0.5. I am doing this so I can see when osmosis occurs and at what concentration. Temperature The temperature must be kept constant throughout the experiment because if the particles are heated from a temperature increase, the particles will move faster and are therefore more likely to collide and reaction will be increased. This is called a collision theory. Volume of solution The volume of the solution in the boiling tubes is to be kept at 10cm throughout the experiment to make it a fair test. Shape of discs I will keep the shape of my discs as similar as possible when cutting them, also to ensure a fair test. Age of potato I will try and use potatoes of the same age, as the older the potato is the more shrivelled and dried up it will be. Which means the water levels in the potato may drop and cause the rate of osmosis to be affected. I will also use POTATOES OF THE SAME TYPE as some potatoes may have more or less water molecules once again affecting osmosis. Time experiment is left for All test tubes must be left for the same amount of time, for an accurate set of result to be achieved. Percentage change in mass was my dependant variable. To help me plan my experiment I have done some research about osmosis and matters related to it. This is to help me make prediction and figure out a way to make this investigation fair and safe. Osmosis is the diffusion of water molecules from a weaker solution into a stronger one, through a partially permeable membrane. In this case, the tiny holes in the membrane of the potato cells will allow the water molecules to pass through in and out of the potato cells and the solution, depending on the concentration gradient of the two substances. So in this case, when the water concentration is lower in the cells, the water will go inside the cells of the potato and the potato will gain mass. If there is a higher concentration of water in the potato, the water will go out of the potato cells. When the concentration gradient is lower in the potato cells, the water will transfer from the solution to the potato cells and vice versa. Preliminary work Diagram Method I filled the visking tube with 0.5M of sucrose and placed it in a beaker filled with 0.3 molar of solution. Before I placed the visking tube in the beaker I weighed it, then left it in the beaker for 30 minutes before weighing it again. This experiment allowed me to plan as it gave me an idea what was going to happen in each molarity. The visking tube walls in the experiment were an example of a semi-permeable membrane which the potato cells will be represented by the cell membrane. In the preliminary experiment I used the formula Change in Mass X original Mass Against the molarity of the solution To help me reach the percentage change in mass as I will in my investigation. Prediction In the distilled water I believe that there are less water molecules more concentrated in the potato, and therefore the water molecules should pass by osmosis from the water to the potato making the potato discs increase in mass. The potato cells being surrounded by a weak solution, will be most likely to swell up and become turgid, taking in all the water it can possibly take in. With the potato discs in the molar solutions of sucrose, I don't think there will be much change in the mass of the potato. This is because there isn't much difference between the two substances. I think the mass of the potato discs won't be altered much. With the 0.4 molar solutions of sucrose and 0.5, I predict that these potato discs will lose weight as the solution they are in is high in concentration, so the demand for water molecules from the potato cells will be high. Obtaining evidence Safety I will be using a razor blade to cut the potato with and if not handled properly I could injure myself or others, so I must make sure that the blade is somewhere safe at all times. I also have to make sure the solution doesn't get into my body internally and it could damage me. So if there are any spillages they must be cleared up and I must make sure I wash my hands of any of the solutions at the end of the experiment. Other than these and the usual, keep hair tied back and loose clothes tucked away there weren't any bigger matters to be aware of. Results To find out the percentage change in mass I use this formula which I acquired from my preliminary experiments CHANGE IN MASS X 100 AND DIVIDE BY THE ORIGIONAL MASS Against the molarity of the solution I tried to keep my results accurate by ensuring all my key factors were kept the same. I tried to make everything a fair test and used 10 discs instead of using one disc 3 times to gain better results. As you can see in the graph above I have ringed all the anomalous results. The experiment should have been left for 24hours but instead was left for a week which in turn meant osmosis had a longer time to take place. The evidence shows that my prediction was right as my results collaborate with my predictions. The potato cells took in or gave out water molecules depending on the concentration of the solution it is surrounded in. Analysing and evaluating evidence As you can see in the graph above I have ringed the 3 anomalous results. The evidence above shows my prediction as being correct as the results collaborate with my prediction. The potato cells took in or gave out water molecules depending on the concentration of the solution it is surrounded in. my first result was from the distilled water. I would have expected it to be about 24.55 whereas it was 13.62. This anomalous result may have been caused by an inaccurate sizing of the potato discs, or the fact that the experiment was left for 6 days too long. My second anomalous result was at the molarity of 0.3 and was 00.87. I would have expected this result to be at 0.26, this anomaly may have been caused by, again inaccurate sizing of potato discs. The concentration of the solution may not have been quite right, they're could have been a temperature change that has affected that test tube, and the experiment was left for too long. My 3rd anomalous result was at a molarity of 0.4, at -11.13. This result wasn't too incorrect as I would have expected it to be around 12.5. This anomaly could have been gained by any of the reasons I have stated for the last anomaly but seeing as it is close to being correct I think it was probably a minor fault such as inaccurate sizing of the potato discs or temperature change, which were hard to control in this experiment. The other 3 results though are all correct due to all the key factors being controlled well during those 3 experiments. Evaluation Our experiment went well, excluding the anomalous results acquired. The method we used was easy and effective but I'm not sure if an accurate conclusion could be achieved due to too many anomalies in my results. I would have liked to have taken in my results after 24hours but this was not possible. It would have also been better if I could find a more accurate way of getting the potato discs to be the same shape and size as this may have eliminated some of the anomalies. Also if we had done each experiment 3 times as well as still using 10 discs in each test tube our results would have been far more accurate as a better average would be obtained. Using a wider range of molarities, for instance going up in 0.5 or going all the way to 1.00M would have helped me to obtain more accurate results also and would also help to wean out some of the anomalous results to make sure that the results are as accurate as possible. Using 10 discs instead or having to repeat the experiment 3 times was a good idea and saved a lot of time but this also introduced the problem of whether all 10 discs could be kept the same size which was hard to achieve. To take my investigation further, I could also investigate the effect of different potato types on osmosis. To look at how different concentrations of water from different types of potatoes do this I have written up a plan of how this could be done. I will use the same concentrations as used in my last experiment and will use the same equipment as before only this time using 4 different types of potato aswel. Method I will fill each of the boiling tubes with a 3rd of either distilled water or one of the sucrose solutions. Then using a cork borer, or a more accurate piece of equipment if found I will take 6 cylinders of potato from 4 different types of potatoes, and slice up each cylinder into 10 discs each 10mm long and of equall thickness. I will then place each group of 10 discs onto separate pieces of filter paper and weigh them, recording each of the results of each of the different types of potato, drawing up a table like this for each different type of potato. I will then place each group of potato discs onto each of my labelled boiling tubes. After 24 hours I will remove any excess surplus fluid by using filter paper. I will then record the results of each boiling tube for each different type of potato and compare my results. I will as before have key factors to control The size of the potato discs The concentration of the solution The temperature The volume of the solution The shape of the discs The age of the potato And the time the experiment is left for.   

Aim to find out if osmosis occurs in a potato, and how it affects the potato in different molar solutions of sucrose and water. Planning Apparatus 6 boiling tubes Sucrose solution Balance – 2dp for more accurate results Distilled water Razor...

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