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BIOLOGY, M7 2023 HSC 5 MC

An experiment was conducted to investigate the rate of binary fission in E.coli. The results of the experiment are shown.
 

Time (minutes) Number of E.coli
0 20
20 40
40 80
60 160
80 320
100 640

 
Which graph represents the data in the table?
 


  

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\(B\)

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By Elimination:

→ The independent variable (time) must be on the \(x\)-axis (Eliminate C and D).

→ The number of E. Coli starts at 20, not 0 (Eliminate A).

\(\Rightarrow B\)

BIOLOGY, M7 EQ-Bank 12

A practical investigation is to be carried out to test for the microbes found in food.

Complete the table to show how to minimise risks that are likely to arise in carrying out this investigation.   (3 marks)
 

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\begin{array} {|l|l|l|}
\hline \textit{Risk} & \textit{Procedure to minimise it} \\
\hline \text{Infection} & \text{Wear gloves.} \\
\hline \text{Growth of pathogenic} & \text{Incubate < 35° to prevent these microbes from growing.} \\
\hline \text{Cross-contamination} & \text{Sanitise bench and equipment.} \\
\hline \end{array}

Show Worked Solution

\begin{array} {|l|l|l|}
\hline \textit{Risk} & \textit{Procedure to minimise it} \\
\hline \text{Infection} & \text{Wear gloves.} \\
\hline \text{Growth of pathogenic} & \text{Incubate < 35° to prevent these microbes from growing.} \\
\hline \text{Cross-contamination} & \text{Sanitise bench and equipment.} \\
\hline \end{array}

BIOLOGY, M7 2015 HSC 25

A group of students wanted to test whether water purifying tablets were effective in making creek water free from bacteria.

They conducted an experiment using a water sample collected from the creek and found that the tablets were effective.

  1. Describe a means of addressing ONE identified hazard relevant to this investigation.   (2 marks)

  2. Illustrate the results of this experiment in diagrammatic form.
  3. Use labels to clearly identify the data collected.   (3 marks)
     
     

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a.   Successful answers could include one of the following:

→ A pathogenic microbe might be cultured during the process.

→ Post experiment, agar plates must be heated under high pressure to kill any microbes cultured before disposal.
  

b.   Results of experiment:

Show Worked Solution

a.   Successful answers could include one of the following:

→ A pathogenic microbe might be cultured during the process.

→ Post experiment, agar plates must be heated under high pressure to kill any microbes cultured before disposal.
  

b.   Results of experiment:

BIOLOGY, M7 2019 HSC 7 MC

Two types of bacteria were isolated from a patient's throat swab and grown in pure culture on separate agar plates. On each plate there were FOUR different antibiotic discs, `W, X, Y` and `Z`.

The photograph shows the plates seven days later.
 

Which antibiotic should be used to treat the patient?

  1. `W`
  2. `X`
  3. `Y`
  4. `Z`
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`A`

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→ The area of each circle shows the amount of bacterial growth each antibiotic has inhibited.

→ The larger the circle, the more effective that antibiotic is at inhibiting bacterial growth.

→ Antibiotic `W` has the most consistently large disc, and should be used to treat the patient.

`=>A`

BIOLOGY, M7 2020 HSC 7 MC

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 and placed them in an incubator set to 25°C.

Which row of the table represents a valid design for the investigation?
 

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`A`

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→ The different food samples are deliberately selected (independent).

→ The number of microbes is a consequence of the specific food samples (dependent).

→ An agar plate with a food sample would be a base of comparison (experimental control) while temperature would be a controlled variable.

`=>A`

♦ Mean mark 49%.

BIOLOGY, M7 2021 HSC 16 MC

Scientists conducted an experiment to investigate the effectiveness of treating water from storage dams with UV radiation.

The experiment was conducted more than three times. The results are shown in the table.
 

What conclusion may be drawn from the data obtained?

  1. The control plates are contaminated.
  2. High doses of UV eliminate all pathogens.
  3. Exposure to UV inhibits reproduction of bacteria.
  4. The presence of bacteria reduces the amount of UV.
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`C`

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→ As the UV dose increased, the number of bacteria decreased.

`=>C`

♦ Mean mark 79%.