Biology A2

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level

* 2 3 0 8 9 6 9 9 7 3 *

BIOLOGY Paper 5 Planning, Analysis and Evaluation Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black ink. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

9700/51
October/November 2011 1 hour 15 minutes

For Examiner’s Use 1 2 Total

This document consists of 8 printed pages.
DC (CB (SE/DJ)) 34786/4 © UCLES 2011

[Turn over

2 1 Photosynthesis was investigated in a species of unicellular alga using the apparatus shown in Fig. 1.1. suspension of unicellular algae in water For Examiner’s Use

10.0 light of known wavelength oxygen probe magnetic stirrer Fig. 1.1 Two different strains of the species of alga were tested using a range of different wavelengths of light. • • Light of known wavelength was passed through the tube containing algae for two hours. The light transmission through the suspension and the oxygen concentration were then measured. light meter oxygen meter

The results were used to plot the absorption spectrum and the action spectrum for each strain of alga. Fig.1.2 shows these spectra. strain A strain B absorbance absorption spectra

400

500 600 700 wavelength of light / nm

rate of photosynthesis

action spectra

400

500 600 700 wavelength of light / nm

Fig. 1.2
© UCLES 2011 9700/51/O/N/11

3 (a) (i) State the two dependent variables in this investigation. 1. .............................................................................................................................. 2. .......................................................................................................................... [2] (ii) Apart from temperature and pH, which have little effect, state two variables that should be standardised during this investigation. 1. .............................................................................................................................. 2. .......................................................................................................................... [2] (b) (i) Water with no suspended algae transmits 100% of the light. State how the data to plot the absorption spectrum was obtained. .................................................................................................................................. ............................................................................................................................. [1] (ii) State the data which would be used to plot the action spectrum. ............................................................................................................................. [1] The photosynthetic pigments of the algae were extracted and were separated by two-way chromatography. The pigments were first separated by one solvent and then separated again by a second solvent at right angles to the first solvent. Fig. 1.3. shows the results for the two different strains. strain A solvent front 1 4 3 2 direction of first solvent 1 origin 6 1 origin 5 3 2 6 strain B 5 solvent front 1 For Examiner’s Use

solvent front 2 direction of second solvent Fig. 1.3

solvent front 2

(c) Using the information in Fig.1.3, suggest why using two different solvents gives a better separation of these pigments than just using one solvent. .............................................................................................................................................
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