（c）Fig． 2.3 shows a Galapagos penguin，Spheniscus mendiculus，swimming in the water． Fig． 2.3 Penguins are birds that live on land but spend a lot of time swimming underwater hunting for food．Penguins can remain underwater for up to twenty minutes．During this time they do not breathe but their tissues continue to respire． Haemoglobin in the red blood cells of penguins has a higher affinity for oxygen than haemoglobin in other birds that do not swim underwater． Fig． 2.4 shows the oxygen dissociation curve for a bird that does not swim underwater． （i）Draw a line on Fig． 2.4 to suggest the position of the oxygen dissociation curve for penguin haemoglobin． ［2］ of haemoglobin with oxygen (ii) Penguin haemoglobin is very sensitive to a decrease in pH caused by an increase in the carbon dioxide concentration in the blood. Explain how a decrease in pH affects penguin haemoglobin, and suggest how this helps the penguin to swim underwater for a long time. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . .................................................................................................................................

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