Biology · 2005 · May · Paper 2 · HL · TZ2 · Question paper

2205-6014 8 pages M05/4/BIOLO/HP2/ENG/TZ2/XX+ Wednesday 11 May 2005 (afternoon) BIOLOGY HIGHER LEVEL PAPER 2  IB DIPLOMA PROGRAMME PROGRAMME DU DIPLÔME DU BI PROGRAMA DEL DIPLOMA DEL BI INSTRUCTIONS TO CANDIDATES • Write your session number in the boxes above. • Do not open this examination paper until instructed to do so. • Section A: answer all of Section A in the spaces provided. • Section B: answer two questions from Section B. Write your answers on answer sheets. Write your session number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided. • At the end of the examination, indicate the numbers of the questions answered in the candidate box on your cover sheet and indicate the number of sheets used in the appropriate box on your cover sheet. 2 hours 15 minutes [Personal identifier removed] [Personal identifier removed] 0108 2205-6014 – 2 – M05/4/BIOLO/HP2/ENG/TZ2/XX+ SECTION A Answer all the questions in the spaces provided. 1. Rats were bred for several generations to prefer alcohol (ethanol) consumption. When tested, it was discovered that the brains of these rats possessed lower quantities of the chemical neuropeptide Y (NPY). To test the hypothesis that lower quantities of NPY leads to a preference for alcohol, rats were genetically engineered to be NPY deficient (genotype NPY –/–), or to produce an excess of NPY (NPY-EX). In separate experiments, the two groups were compared to normal rats (in terms of their alcohol preference) possessing the genotype NPY +/+. The groups were offered solutions of increasing alcohol concentration. The quantity of each solution consumed per day was measured. Consumption / g kg– 1 day–1 Figure 1 Concentration of alcohol solution / % Consumption / g kg– 1 day–1 Figure 2 Concentration of alcohol solution / % [Source: adapted from Thiele et al., Nature, (1998), 396 pages 366–369] (a) Calculate the difference in