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Investigate the factors that affect the growth rate of a population (plant).

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Growth Population of Duckweed Task Investigate the factors that affect the growth rate of a population (plant). Prediction I would predict that the following factors could make a difference to how well a plant population increases. Factor (Variable) Why it makes a difference How we could control for an investigation Light need To photosynthesise put paper around jars Temperature enzymes grow faster put more in same room pH to acidic to alkaline, plant will die use universal indicator to control Method In order to see a change in a population we will need to select a plant that reproduces rapidly so we will use duckweed which reproduces asexually. We will set up duckweed plants in different conditions to see how they react to different light intensities and with different amount of fertilizers as shown below. ...read more.


No light was when the light had to pass through black sugar paper and there was a reading of 33%. Each experiment was carried out twice and both sets of results can be seen above, and then followed by the average of the two brackets. In full light the duckweed population grew with and without fertilizer. It had a steady rate of growth, but each week it went up, some times by a substantial amount and sometimes with a minimal amount. In partial light the duckweed population grew but very slowly. At all times the population was around the same mark. There was a slight drop of the duckweed population towards the end of the experiment, at day 42 all of the tests died out causing the population of duckweed to decrease. ...read more.


Evaluation This has been an event full experiment, but it wasn't really a fair test. There are many factors that I would change if I was to do the experiment again. Counting duckweed isn't very accurate as each individual duckweed could weigh a different weight. I would weigh the duckweed next time and make sure I have them all the same weight, so then it is more reliable. I would also do the experiment in different conditions, such as temperature, I would try it in a fridge, body temperature, a greenhouse and at room temperature. There is a slight disadvantage to doing this at room temperature as the room temperature is not the same all the time, and if I was to put the experiment in the fridge it wouldn't see natural sunlight and photosynthesis may not take place. My prediction is well founded because of what happened in the results, ...read more.

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