Biology · May / June 2024 · Paper 61 · Question 2
0610
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The question as text
Plan an investigation to determine the effect of light intensity on photosynthesis in an aquatic plant. [6]
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independent variable
1
(at least) idea of two / different, light intensities ; dependent variable
2
(measuring) volume of, gas / oxygen, produced OR counting (number of) bubbles ;
3 and 4 detail of method ;;
max two from:
method of changing light intensity
e.g. different lamp distances / dimmer switch altered / different bulbs
method of, collecting gas / measuring volume of gas e.g. use of a gas syringe / ref to any quantitative displacement method
method to avoid heating effect of light e.g. heat shield / use LED bulbs to prevent heating
keep plant submerged / water added to cover the plant / weighing the plant down
idea of time for acclimatisation at each new light intensity / equilibration
5 and 6 constant variables ;;
max two from:
time or volume (depending on method used) e.g., time to collect a set volume of oxygen / time to count number of bubbles OR volume / number of bubbles, in a set time
concentration of hydrogencarbonate added or same source of carbon dioxide
colour / wavelength, of light
temperature
same, type / species / (named) plant / age
7
two or more repeats ;
8
relevant safety ;
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