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Biology A2

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.

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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. 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. . 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] (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. . 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. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………. [2] © UCLES 2011 9700/51/O/N/11 [Turn over 4 (d) Outline a procedure that a student could use to extract the photosynthetic pigments and obtain these chromatograms. ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………….. ……………………………………………………. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………. [8] For Examiner’s Use UCLES 2011 9700/51/O/N/11 5 (e) Different photosynthetic pigments absorb different wavelengths of light. Table 1. 1 shows some information about the pigments, P, Q, R, S and T, found in these unicellular algae, including the wavelength of light at which maximum light absorption occurs. Table 1. 1 pigment wavelength of light / nm 620 545 and 547 420 and 660 490 430 and 645 Rf value solvent 1 0. 20 0. 60 0. 65 0. 91 0. 82 solvent 2 0. 89 0. 29 0. 11 0. 19 0. 92 For Examiner’s Use P Q R S T Rf = distance moved by pigment distance moved by solvent front

One of the strains of algae lacks one of the pigments. Using the information in Table 1. 1, Fig. 1. 2 and Fig. 1. 3: (i) identify the strain of alga that lacks one of these pigments and state the letter of the missing pigment …………………………………………………………………………………………………………….. [1] (ii) state the evidence that supports your answer to (i). …………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………….. [2] (iii) In water, the shorter the wavelength of light, the deeper it travels. Suggest why it is an advantage to have the pigment that you identified in (i). ………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………….. [1] [Total: 20] © UCLES 2011 9700/51/O/N/11 [Turn over 2 A student carried out some investigations into the inheritance of body colour and wing length in the fruit fly, Drosophila melanogaster, to test the hypothesis: The inheritance of body colour and wing length in fruit flies is controlled by two genes on separate chromosomes. The student carried out three genetic crosses. To carry out each cross the following procedure was used: • • • male and virgin female adult fruit flies were placed into a breeding unit containing a culture medium for their larvae after mating and egg laying, the adult fruit flies were removed newly emerged adult fruit flies were sexed by observing the shape of the last

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