26 9 Weddell seals spend a lot of their time swimming underwater, diving to find food and diving to avoid predators. However, they do have to come to the surface to breathe. (a) The graphs give some information about dives by Weddell seals. Length of dive / mins 40 30 20 10 0 Percentage of dives (%) 0–5 6–10 11–15 16–20 21–25 26–30 31–35 36–40 41–45 46–50 51–55 56–60 60+ Depth of dive / m 25 20 15 10 5 Percentage of dives (%) 0–50 51–100 101–150 151–200 201–250 251–300 301–350 351–400 401–450 451–500 501–550 551–600 0 Turn over 27 Turn over Comment on the conclusions that can be made about the dives of these seals. 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(b) Weddell seals carry higher concentrations of oxygen in their bodies than humans. (i) The haemoglobin of Weddell seals is adapted to carry higher levels of oxygen than the haemoglobin of humans, at each partial pressure of oxygen. Which row of the table describes the haemoglobin of the Weddell seal? (1) Position of oxygen dissociation curve compared with human haemoglobin Affinity for oxygen compared with human haemoglobin A to the left higher B to the left lower C to the right higher D to the right lower 28 *(ii) The table shows how much oxygen is stored in different parts of the body of humans and Weddell seals. Part of body Total oxygen stored / a.u. kg–1 body tissue humans Weddell seals lungs 12 3 blood 10 58 muscle 2 23 body fluids, other than in the blood 2 2 Weddell seals also store erythrocytes in their spleen that are released into the bloodstream during deep dives. Turn over 29 Analyse the data to explain the differences between these two mammals. 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..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................................................................... 30 (c) An investigation studied the change in the concentration of oxygen in the blood and muscles of a Weddell seal during a dive. The graph shows the results of this investigation and the diagram shows part of the circulation of blood in the seal during the dive. Concentration of oxygen Start of dive 0 End of dive brain lung heart in blood in muscles Time Key oxygenated blood deoxygenated blood Analyse the data to explain these results. 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Concentration of lactic acid / a.u. muscles Time after the end of the dive / mins 100 80 60 40 20 0 0 10 20 30 40 50 60 blood Explain the importance of these changes after the Weddell seal comes to the surface to breathe. 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(Total for Question 9 = 17 marks) TOTAL FOR PAPER = 90 MARKS 32 BLANK PAGE