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CAIE A-Level Biology A2 13.2.4 Whole Plant Photosynthesis Investigation Questions

Explain whole-plant photosynthesis investigations using evidence from each question and mark scheme.

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • Explain whole-plant photosynthesis investigations.

CAIE A-Level Biology A2 13.2.4 Whole Plant Photosynthesis Investigation Questions question 1

[Maximum number: 5]

Question (a)

(a)

The rate of photosynthesis is affected by many environmental factors.

A student carried out an experiment to investigate the relationship between the concentration of carbon dioxide available to an aquatic plant, Cabomba caroliniana, and its rate of photosynthesis.

Fig. 1.1 shows the experimental set-up for this investigation.

Fig. 1.1 shows the experimental set-up for this investigation.

- Sodium hydrogencarbonate solution was used as a source of carbon dioxide.
- The concentration of carbon dioxide was varied using six different concentrations of sodium hydrogencarbonate solution.
- All C. caroliniana plants were kept in the dark before the light was switched on at the start of the experiment.
- Five replicates were carried out at each concentration.
- The rate of photosynthesis was obtained by calculating the percentage change in dissolved oxygen concentration in the solution over five minutes.

Fig. 1.2 shows the results of the investigation.

Fig. 1.2

Fig. 1.2

[ 5 ]

Question (i)

(i)

The percentage change in dissolved oxygen for C. caroliniana at 0.00moldm−30.00 \mathrm{moldm}^{-3} of sodium hydrogencarbonate solution is negative.

Suggest reasons for this negative value.

[ 2 ]

Question (ii)

(ii)

To minimise temperature changes, the student decided to use an LED lamp as a light source. LED lamps release very little heat energy.

Explain the importance of minimising temperature changes in this experiment.

[ 3 ]
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