Biology · 2017 · May · Paper 2 · HL · TZ1 · Question paper

24EP01 M17/4/BIOLO/HP2/ENG/TZ1/XX © International Baccalaureate Organization 2017 2217 – 6008 2 hours 15 minutes 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 questions. • Section B: answer two questions. • Write your answers in the boxes provided. • A calculator is required for this paper. • The maximum mark for this examination paper is [72 marks]. [Personal identifier removed] Monday 1 May 2017 (afternoon) Biology Higher level Paper 2 Section A Answer all questions. Write your answers in the boxes provided. 1. The Chinese soft-shelled turtle, Pelodiscus sinensis, lives in salt water marshes. The turtle can live under water and out of water. These turtles have fully developed lungs and kidneys, however, many microvilli have been discovered in the mouth of P. sinensis. A study was undertaken to test the hypothesis that oxygen uptake and urea excretion can simultaneously occur in the mouth. Initial experiments involved collecting nitrogen excretion data from P. sinensis. The turtle urinates both in water and out of water. When in water it allows waste products to be washed out of its mouth. When out of water it regularly dips its head into shallow water to wash its mouth. The table shows the mean rates of ammonia and urea excretion from the mouth and kidney over six days. Excretion of nitrogen by the mouth / µmol day-1 g-1 turtle Excretion of nitrogen by the kidney / µmol day-1 g-1 turtle Turtle submerged in water Turtle out of water Turtle submerged in water Turtle out of water Ammonia 0.29 0.30 0.63 0.54 Urea 0.90 1.56 0.07 0.73 [Source: Reproduced with permission, Y. Ip et al. (2012) The Journal of Experimental Biology, 215, pages 3723—3733. jeb.biologists.org. doi: 10.1242/jeb.068916] (a) Deduce whether the excretion of ammonia or urea changes more when a turtle emerges from water. [2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .