Biology practical write-up example

I have never done this experiment. The results are fictitious. I prepared this purely to give students an example of how a simple biology investigation could be written up.

The effect of Coca-Cola on the growth of plants


To investigate the effect that Coca-Cola has upon growing plant seedlings.


It is expected that plants watered with Coca-Cola will grow poorly, compared with those given pure water. This is because Coca-Cola contains acid, and plants are sensitive to acidity in the soil.


Two young bean seedlings were grown. One was watered twice every week with 200ml of pure water; the other was watered twice every week with 200ml of Coca-Cola. The heights of the seedlings were measured using a ruler every three days, and the results were recorded. To ensure that the experiment was fair, both plants were kept at the same temperature and given the same amount of light.


The heights of the two seedlings are shown in the table below.

Day Height of seedling given pure water Height of seedling given Coca-Cola
0 6 cm 6 cm
3 8 cm 8 cm
6 10 cm 9 cm
9 12 cm 10 cm
12 14 cm 10 cm
15 16 cm 10 cm

Analysis of results

The seedling given pure water grew at a steady rate throughout the experiment. However, the growth of the seedling given Coca-Cola slowed down, and it stopped growing completely after 9 days. This is illustrated by the graph below.


The results of this experiment clearly support the hypothesis: the seedling given pure water grew better than the seedling watered with Coca-Cola.


The experiment produced a reasonably clear result. However, to ensure that the result is valid, it would be a good idea to repeat the experiment with several different seedlings, instead of only using two. Future experiments could also be carried out in which seedlings were given a pure solute of dilute acid instead of being given Coca-Cola. This would help prove that the plants are being damaged by the acid in the Coca-Cola and not by some other ingredient (such as the sugar or the caffeine).

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© Andrew Gray, 2005