ExpertMedium1 markMultiple Choice
AQA GCSE · Question 03.4 · Homeostasis and Response
The student wanted to make the investigation of the effect of one-sided light more valid. The student decided to set up a third experiment. How should the student set up the third experiment?
The student wanted to make the investigation of the effect of one-sided light more valid. The student decided to set up a third experiment. How should the student set up the third experiment?
Answer options:
A.
Give no water to the third seedling.
B.
Shine light from all sides on the third seedling.
C.
Turn the third seedling so it is upside-down.
How to approach this question
To improve validity, a new experiment should help confirm that the direction of light is the key factor. Experiment 1 used one-sided light. Experiment 2 used no light. A good third experiment would be to use light that is not one-sided (i.e., from all sides or from directly above) to see if the shoot grows straight.
Full Answer
B.Shine light from all sides on the third seedling.✓ Correct
A valid investigation needs proper controls to ensure the conclusion is correct. The original experiment compared one-sided light (Experiment 1) with no light (Experiment 2). To further confirm that the *direction* of the light is what causes bending, a third experiment with light from all sides (or directly overhead) should be set up. In this condition, the shoot should grow straight up, just like in the dark. This strengthens the conclusion that it is the uneven distribution of light that causes the bending.
Common mistakes
✗ Choosing an option that changes a different variable, like water. This would not help validate the conclusion about light.
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