Figure 2 shows colonies of bacteria growing on an agar plate - Edexcel - GCSE Biology Combined Science - Question 2 - 2023 - Paper 1

To find the number of bacteria after five hours, we first determine how many 30-minute intervals are in five hours:

$5 \text{ hours} = 5 \times 60 \text{ minutes} = 300 \text{ minutes}$

The number of 30-minute intervals is:

$\frac{300 \text{ minutes}}{30 \text{ minutes}} = 10 \text{ intervals}$

Since the bacteria double in number every interval, the formula for exponential growth is:

$N = N_0 \times 2^n$

Where:

• $N_0$ is the initial amount of bacteria (1 in this case)
• $n$ is the number of intervals (10 in this case)

Thus, the calculation becomes:

$N = 1 \times 2^{10} = 1024$

Therefore, after five hours, there will be 1024 bacteria in the colony.