Biology · 2007 · May · Paper 2 · SL · TZ2 · Question paper

2207-6017 10 pages M07/4/BIOLO/SP2/ENG/TZ2/XX Monday 14 May 2007 (afternoon) Biology Standard 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 one question 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. 1 hour 15 minutes [Personal identifier removed] © IBO 2007 0110 22076017 2207-6017 – 2 – M07/4/BIOLO/SP2/ENG/TZ2/XX Section a Answer all the questions in the spaces provided. 1. A coral polyp is a marine organism, characterized by a hard skeleton. Coral reefs are colonies of numerous individual polyps. Coral polyps often form close associations with tiny plants such as algae. The algae, which live within the tissues of the polyp, give the coral its unique colour. The algae receive nutrients from their host and provide the host with a food source in return. When coral undergoes environmental stress it expels algae from its polyps and the coral appears white. This process is called “coral bleaching”. The graph below indicates the number of coral reef areas showing bleaching over a 20-year period off the coast of Australia. The arrows indicate the occurrence of El Niño, an event that brings effects such as an increase in water temperature around the coral. Number of coral reef areas showing bleaching 12 10 8 6 4 2 0 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Year [Source: adapted from M Spalding, K Teleki, and T Spencer, (1999), Climate Change and Coral Bleaching, UNEP World Conservation Monitoring Centre, www.unep-wcmc.org/climate/climate%20report.htm, reprinted with permission of the authors] (a)