Students designed and conducted an investigation to test for the presence of microbes in THREE different food samples - HSC - SSCE Biology - Question 7 - 2020 - Paper 1
Question 7
Students designed and conducted an investigation to test for the presence of microbes in THREE different food samples.
They inoculated agar plates with the samples ... show full transcript
Worked Solution & Example Answer:Students designed and conducted an investigation to test for the presence of microbes in THREE different food samples - HSC - SSCE Biology - Question 7 - 2020 - Paper 1
Step 1
Identify the Independent Variable
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Answer
The independent variable is the factor that is manipulated in the investigation. In this case, it should be the 'Food sample' as different samples are used to test for microbes.
Step 2
Identify the Dependent Variable
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Answer
The dependent variable is what is measured in the experiment. Here, it should be 'Number of microbes' since the aim is to count the microbes present in the different food samples.
Step 3
Identify the Experimental Control
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The experimental control should be a condition that remains constant to ensure that the experiment is valid. An appropriate control in this context would be 'An agar plate without a sample' to compare against the samples inoculated with food.
Step 4
Select the Valid Row
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Answer
Given the above definitions, the valid design for this investigation is represented by option A:
Independent Variable: Food sample
Dependent Variable: Number of microbes
Experimental Control: An agar plate without a sample.
