Using data from Figure 14, calculate the difference in the population size from March to July - Edexcel - GCSE Biology - Question 9 - 2022 - Paper 1

To calculate the population size for both March and July, we can use the given formula:

$\text{population size} = \frac{\text{number marked in the first sample} \times \text{size of the second sample}}{\text{number recaptured in the second sample}}$

March Population Size Calculation:
Substituting the values for March:
$\text{population size} = \frac{18 \times 22}{8}$
Calculating this gives:
$\text{population size} = \frac{396}{8} = 49.5$ (approximately 50)

July Population Size Calculation:
Substituting the values for July:
$\text{population size} = \frac{12 \times 18}{10}$
Calculating this gives:
$\text{population size} = \frac{216}{10} = 21.6$

Difference in Population Size:
Now, we calculate the difference:
$50 - 21.6 = 28.4$

Therefore, the difference in population size from March to July is approximately 28.4.