Calculate the mean stomatal density in the three fields of view in Figure 9 - AQA - A-Level Biology - Question 9 - 2020 - Paper 1

Assuming the following counts are obtained from the three fields of view:

• Field 1: 10 stomata
• Field 2: 11 stomata
• Field 3: 8 stomata

Total stomata count = 10 + 11 + 8 = 29 stomata.

Mean stomatal density can be calculated using the formula:

$$Mean ext{ stomatal density} = \frac{Total ext{ stomata}}{Total ext{ area in } mm^2}$$

In our case, the total area for three squares is:

$$Total ext{ area} = 3 imes 0.0625 ext{ mm}^2 = 0.1875 ext{ mm}^2$$

Now substituting the values:

$$Mean ext{ stomatal density} = \frac{29}{0.1875} \approx 154.67 ext{ stomata per mm}^2$$

After rounding, the final answer is approximately 155 stomata per mm².