Fig. 4.1 shows a Siamese fighting fish that lives in fresh water. large colourful fin location of an organ that can be filled with atmospheric air magnification ×50000 [Figure 4.1] Fig. 4.2 shows the effect of changing pH on the solubility of oxygen in water. 100 80 percentage solubility of oxygen in water 60 40 20 0 6.0 6.5 7.0 7.5 8.0 8.5 9.0 pH of water [Figure 4.2] Fig. 4.3 shows the effect of changing temperature on the solubility of oxygen in water. 15 14- 13 12- 11 oxygen solubility in water /mg per dm³ 10- 9 8- 7 6- 5+ 0 5 10 15 20 25 30 35 40 45 50 temperature of water/°C [Figure 4.3]

1. (a)(i)Siamese fighting fish live in shallow water that can range in pH from 6.9 to 8.2 and in temperature from 15°C to 40°C. Use the information in Fig. 4.2 and Fig. 4.3 to explain how the conditions in which these fish live may be challenging.[3]
2. (a)(ii)All fish have gills that provide a gas exchange surface in water. Siamese fighting fish also have an organ that has similar features to those of a human lung. These fish swim to the surface of water to take air from the atmosphere into this organ. Explain the advantage to Siamese fighting fish of also having this organ.[4]
3. (b)(i)Siamese fighting fish have 42 chromosomes in each diploid cell. State each of the following. the named structure in each diploid cell that contains the chromosomes[1]
4. (b)(ii)the type of nuclear division that produces gametes[1]
5. (b)(iii)the number of chromosomes in each gamete of the Siamese fighting fish.[1]
6. (c)The dramatic shape and colour of Siamese fighting fish are produced by selective breeding. Suggest how the process of selective breeding in Siamese fighting fish can be used to produce these desirable features.[5]

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