Primary Science – Bacteria and Fungi
Bacteria Growth Experiment
This science revision note aims to help your child:
– Analyse the factors affecting the growth of the bacteria (based on this experiment).
– Make inferences from the graph and the statements in the question.
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Joy had a pot of rice. She distributed the rice evenly into 4 similar bowls and placed them in 4 different locations for 2 days.
She then did a test to find the amount of bacteria in each bowl of rice and plotted her results in the graph as shown below.
Based on the graph above, which of the following statements is false or not possible to tell?
1) Light affects bacteria growth.
2) The best place to safely store rice is in the freezer.
3) Bacteria grows better with warmth rather than in the cold.
4) The bacteria will grow faster when there is more water added to the bowls.
Let’s go through each option to determine if it is correct.
OPTION 1 – Light affects bacteria growth.
Now, look for 2 bowls that have the presence of light as the changed variable, with all other variables remaining the same – Bowls C and D.
With the presence of light as the changed variable, did the amount of bacteria in the bowl change?
Yes, as seen in the graph, the amount of bacteria in bowls C and D are different.
Hence, this statement is true, light affects the bacteria growth.
However, if I compare bowls A and B, why did the amount of bacteria is the same even though bowl B is exposed to light? The reason is the temperature inside the freezer is too low. The bacteria need an optimal temperature to grow. Please see the option 3 explanations below for more details.
OPTION 2 – The best place to safely store rice is in the freezer.
The best place to safely store rice would be the location that had the least amount of bacteria. Which location is this? The freezer. Hence, this statement is true.
OPTION 3 – Bacteria grows better with warmth rather than in the cold.
Look for bowls that have the level of cold/warmth as the changed variable. We can compare the bowls in the freezer with the bowl in the room.
The freezer is colder than the room. You can see the amount of bacteria in the freezer is lower than in the room.
Hence, this statement is true as the warmer the bowl of rice is, the greater the amount of bacteria in it.
OPTION 4 – The bacteria will grow faster when there is more water added to the bowls.
It is not possible to tell.
We need to conduct a separate experiment – one bowl of rice with water and the other similar bowl of rice without water. All other variables are kept the same. Only then can we determine if option 4 is true or false.
FINALLY, choose the correct answer.
The answer is 4.
Additional learning material for this topic
Do read the mouldy bread experimental-based question >>> https://scienceshifu.com/primary-science-bacteria-and-fungi-topic-mouldy-bread/
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