A-Level Edexcel Biology AS Dispersion and Range

A-Level Edexcel Biology AS Dispersion and Range
Pearson Edexcel International Advanced Subsidiary/Advanced Level in Biology, Issue 2, February 2021Biology XBI11/YBI11

Review A-Level Edexcel Biology dispersion, standard deviation and range through the available evidence on mean-and-range calculations in inhibition-zone data.

How this is tested

  • calculate maximum differences from mean and range values in biological data tables

Question 5(c)(ii)

[Maximum number: 1]

Listeria monocytogenes is a bacterium that contaminates food and causes the disease listeriosis.

The photograph shows a colony of these bacteria, as seen using an electron microscope.

Figure for Question 5(c)(ii) — Edexcel A-Level Biology AS

The photograph shows green algae called sea lettuce (Ulva lactuca).

Figure for Question 5(c)(ii) — Edexcel A-Level Biology AS

Sea lettuce contains chemicals called fucoxanthins that have antimicrobial properties.

The antimicrobial properties of these chemicals were investigated.
Discs containing fucoxanthin chemical were placed onto four agar plates each seeded with a different type of bacteria.

These plates were then incubated for 24 hours at 25∘C25^{\circ} \mathrm{C} and the zone of inhibition measured.

The diagram shows the zone of inhibition.

Figure for Question 5(c)(ii) — Edexcel A-Level Biology AS

The table shows the results of this investigation.

Table for Question 5(c)(ii) — Edexcel A-Level Biology AS

The table shows the mean and the range of the diameter of the zone of inhibition for each type of bacteria.

Calculate the maximum difference in the diameter of the largest and smallest zones of inhibition.

Answer mm