In an investigation on the growth of leaf yeasts, three malt agar plates were setup as shown in the table and stored in an incubator at 25°C for 7 days - Leaving Cert Biology - Question b - 2021
Question b
In an investigation on the growth of leaf yeasts, three malt agar plates were setup as shown in the table and stored in an incubator at 25°C for 7 days.
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Worked Solution & Example Answer:In an investigation on the growth of leaf yeasts, three malt agar plates were setup as shown in the table and stored in an incubator at 25°C for 7 days - Leaving Cert Biology - Question b - 2021
Step 1
What is the purpose of malt in these plates?
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Answer
The primary purpose of malt in these plates is to provide nutrients or food for the yeasts. It contains essential carbohydrates, proteins, and vitamins that promote the growth of yeast colonies.
Step 2
Why was the underside of the leaf facing the agar?
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Answer
The underside of the leaf was facing the agar to maximize the contact area between the yeast present on the leaf's surface and the agar. This positioning allows for better transfer of yeast cells to the nutrient medium, facilitating growth.
Step 3
What is the purpose of plate A in this investigation?
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Plate A serves as a control in this investigation. It remains unopened to compare the results with plates B and C, helping to determine the effect of the leaf discs on yeast growth without external contamination.
Step 4
Identify the colour of the leaf yeast colonies on plate B.
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The colour of leaf yeast colonies on plate B is pink.
Step 5
Suggest one reason for the difference in results between plates B and C.
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One reason for the difference in results between plates B and C could be the level of pollution. The quiet rural setting of plate B likely has less pollution compared to the busy urban setting of plate C, which may expose the yeasts to harmful chemicals such as smoke or sulfur dioxide.
Step 6
Describe two specific techniques that were carried out in this investigation to prevent the growth of other microbes.
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Wipe surfaces and equipment with disinfectant (antiseptic or alcohol) before use to reduce microbial load.
Use gloves while handling samples and wash hands afterward to minimize contamination risk.
Step 7
State one correct disposal method for these plates after the investigation.
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Soaked in disinfectant (or named disinfectant) or autoclaved (allow pressure cooker) or use of a biohazard bag.
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