A student plans an investigation using mould - AQA - GCSE Biology - Question 4 - 2018 - Paper 1

1. Cut a specified number of slices of bread to the same size to ensure consistency.
2. Place the same number of mould spores on each slice of bread, ensuring that the quantity is the same for each piece.
3. Place each slice in separate sealable plastic bags to create a controlled environment.
4. Store the bags in different locations with varying temperatures: one set at 42 °C and another at 14 °C, to test the hypothesis.
5. Leave each set for the same duration to record growth over time.
6. Measure the percentage cover of mould on each piece of bread after the incubation period.
7. Repeat the experiment to validate results.

The size of the slices of bread should be controlled to ensure consistent surface area for mould growth.

To determine the rate of mould growth, use the formula:

$ext{Rate of growth} = \frac{\text{Amount of mould on day 7} - \text{Amount of mould on day 2}}{\text{Number of days}}$

By examining Figure 3, you can identify the amount of mould on day 2 (10 units) and on day 7 (52 units), yielding:

$\text{Rate of growth} = \frac{52 - 10}{5} = \frac{42}{5} = 8.4 \text{ units per day}$.