Biology · 2010 · May · Paper 2 · HL · TZ1 · Question paper

2210-6008 10 pages M10/4/BIOLO/HP2/ENG/TZ1/XX Monday 17 May 2010 (afternoon) Biology HigHER lE vEl Pa PER 2 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] © International Baccalaureate Organization 2010 0110 22106008 2210-6008 – 2 – M10/4/BIOLO/HP2/ENG/TZ1/XX Section a Answer all the questions in the spaces provided. 1. During aerobic cell respiration, oxygen is consumed and carbon dioxide is produced inside cells. This generates concentration gradients between respiring cells and the environment, which cause diffusion of oxygen and carbon dioxide. Both oxygen and carbon dioxide are soluble in water. As the temperature rises, water becomes saturated at a lower concentration of the gas. Laternula elliptica is a mollusc that lives on the sea bed in Antarctica. Its body temperature is always similar to that of the environment around it. To investigate the effect of temperature on Laternula elliptica , specimens were kept in temperature-controlled aquaria. The oxygen concentrations of water near the gills and in the body fluids were measured, at a range of temperatures from 0 °C to 9 °C. The graph below shows the mean results. Oxygen concentration / % oxygen saturation 40 35 30 25 20 15 10 5 0 0 2 4 6 8 10 Water temperature / °C Key: water near gills body fluids [Source: Hans O Pörtner, Lloyd S Peck and Timo Hirse, “Hyperoxia alleviates thermal stress in the Antarctic bivalve, Laternula elliptica: evidence for oxygen limited thermal tolerance”, Polar Biology, 2006, 29 (8), pages 688– 693] (This question continues on the following page)