Biology · 2003 · November · Paper 2 · SL · Question paper

BIOLOGY STANDARD LEVEL PAPER 2 Friday 14 November 2003 (afternoon) 1 hour 15 minutes N03/410/S(2) IB DIPLOMA PROGRAMME PROGRAMME DU DIPLÔME DU BI PROGRAMA DEL DIPLOMA DEL BI c 883-144 8 pages [Personal identifier removed] y Write your candidate number in the box above. y Do not open this examination paper until instructed to do so. y Section A: answer all of Section A in the spaces provided. y Section B: answer one question from Section B. Write your answers on answer sheets. Write your candidate number on each answer sheet, and attach them to this examination paper and your cover sheet using the tag provided. y At the end of the examination, indicate the numbers of the ques tions answered in the candidate box on your cover sheet and indicate the number of answer sheets used in the appropriate box on your cover sheet. SECTION A Answer all the questions in the spaces provided. 1. Near the middle of pregnancy in humans, the placenta begins to secrete a hormone called corticotrophin-releasing hormone (CRH). CRH influences th e production of hormones which stimulate the development of the fetus. A study was carried out to determine if levels of CRH were correlated with the timing of the baby’s delivery. Blood samples were taken from 500 women during their pregnancies and the concentration of CRH was measured. The women were then divided into three groups according to whether their baby was delivered prematurely, at full-term (about 40 weeks) or late. The graph below shows how the concentration of CRH varied in the mothers’ blood (maternal blood) in each of the three groups during pregnancy. Maternal CRH concentration / pmol 3dm− plasma women who delivered 0 50 100 2015 25 30 Key: women who delivered prematurely women who delivered at full-term late Time since start of pregnancy / weeks [Source: R Smith, Scientific America, (March 1999), pages 68–75] [2] (a) Outline how the concentration of CRH in the blood changes during the pregnancies of women who delivered prematurely.