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Edexcel IAL Biology 6P.3 Experimental design and evaluation

Name the design feature, explain the bias or comparison it controls and suggest a measurable improvement that changes only the intended variable.

Syllabus
First assessment 2019
Course
Biology YBI11
Level
A2

Exam points

  • Justify controls, baselines or solvent-only treatments for a valid comparison.
  • Evaluate sample size, variability, ethics and behavioural effects in a method.
  • Suggest extensions across time, location, species or treatment level with measurements.

6P.3—Experimental design and method evaluation question 1

[Maximum number: 2]

The photograph shows a young locust eating the leaves of a plant.

Figure for Question 6P.3—Experimental design and method evaluation question 1 — Edexcel A-Level Biology A2

Locusts can breed in large numbers and destroy crops, such as sorghum, in East Africa. A scientist observed that some varieties of sorghum were more likely to be eaten by young locusts. The scientist collected the seeds of two varieties of sorghum (A and B) and grew them in trays. Locust eggs were collected and hatched into young locusts. Twenty young locusts were placed in a cage containing 100 g of fresh sorghum leaves of variety A. The cage was kept at 30∘C30^{\circ} \mathrm{C}. After 24 hours, the leaves were removed and the mass of leaves eaten was calculated. This method was repeated with fresh sorghum leaves of variety B. The method was repeated six times for these two varieties of sorghum leaves. The results: Mass of leaves eaten of variety A 17.317.217.517.016.716.9 Mass of leaves eaten of variety B 17.817.917.717.617.817.4

Describe how the student could extend this investigation to collect more data to either support or reject the hypothesis.

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