ExpertMedium1 markShort Answer
AQA GCSE · Question 03.3 · Homeostasis and Response
Why did the student set up experiment 2 in this investigation?
Why did the student set up experiment 2 in this investigation?
How to approach this question
Think about the purpose of a control experiment. A control is used for comparison to show that the factor you are investigating (the independent variable) is the one causing the observed effect. In this case, what is Experiment 2 comparing with Experiment 1?
Full Answer
As a control / to show that the shoot grows upwards without a light stimulus.
Experiment 2 acts as a control for the investigation. By placing a seedling in a light-proof box, the student removes the stimulus of one-sided light. This allows them to see how a seedling grows without this stimulus (it grows straight up). By comparing the result of Experiment 1 (bends towards light) with the control, the student can conclude that it was the one-sided light, and not some other factor, that caused the shoot to bend.
Common mistakes
✗ Just saying "to make it a fair test". You need to be more specific about what it controls for.
✗ Stating that it's to see if the plant can grow without light. While true, its primary purpose in this investigation is for comparison.
Practice the full AQA GCSE Biology Foundation Tier Paper 2
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