24 (B400U20-1) Examiner only 5. Terrestrial organisms obtain oxygen from air. They have internal gas exchange surfaces that provide a large surface area for sufficient diffusion of oxygen and carbon dioxide. (a) (i) State one reason, other than protection, why it is an advantage for gas exchange surfaces to be internal in all terrestrial organisms. [1] (ii) Explain the purpose of ventilation in the lungs of mammals. [1] (b) Graph 5.1 shows changes in volume and pressure in an adult human lung while breathing. Graph 5.1 © WJEC CBAC Ltd. – 0.8 – 0.6 – 0.4 – 0.2 0.2 0 inspiration expiration pleural pressure alveolar pressure lung volume Pressure / kPa 0 0.25 0.5 Volume change / dm3 24 (B400U20-1) Turn over. 25 Examiner only (i) Describe how muscles of the thorax, together with the pleural membranes, cause the change in alveolar pressure seen in Graph 5.1 during inspiration. [4] © WJEC CBAC Ltd. 25 Question continued overleaf 26 (B400U20-1) Examiner only Graph 5.2 illustrates the changes in lung volume for an adult human while breathing at rest. The arrow on Graph 5.2 represents the volume change as this individual breathes in or out. Graph 5.2 © WJEC CBAC Ltd. 0 0 10 20 30 1 3 2 Time / seconds Lung volume / dm3 4 5 (ii) Using the data in Graph 5.2 calculate the total volume of air inspired in one minute when this individual is breathing normally at rest. [2] Total volume inspired in one minute = ........................................................... dm3 26 (B400U20-1) Turn over. 27 Examiner only © WJEC CBAC Ltd. The volume of air inspired and expired is equal, however, the composition of gases varies. Table 5.3 shows the percentage of three gases in air from three points of the breathing cycle. Table 5.3 (iii) The percentage of carbon dioxide in exhaled air is lower than in alveolar air. Explain why. [1] (iv) Exhaled air has a slightly higher percentage of nitrogen than inhaled air despite this gas being inert in mammals. Use the information in Table 5.3 to suggest a reason for the difference. [1] Gas Percentage of gas mixture / % Inhaled (atmospheric) air Exhaled air Alveolar air Oxygen 20.96 16.2 14.0 Carbon dioxide 0.04 4.2 6.4 Nitrogen 79.0 79.6 79.6 27 28 (B400U20-1) Examiner only © WJEC CBAC Ltd. (c) Exposure to cigarette smoke has been shown to have a damaging effect on the lungs and reduce respiratory efficiency. Images 5.4 A and B show two electron micrographs of lung tissue at the same magnification. Image 5.4 A tissue from a lung that has had long-term exposure to cigarette smoke. Image 5.4 B lung tissue that has not been exposed to cigarette smoke. With reference to Images 5.4 A and B, describe one difference in the appearance of the two lung samples and explain how this would decrease gas exchange efficiency. [2] Image 5.4 A Exposed to smoke Image 5.4 B Not exposed to smoke 12 28 (B400U20-1) Turn over. 29 © WJEC CBAC Ltd. 29 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE 30 (B400U20-1) © WJEC CBAC Ltd. 30 6. Image 6 is a photograph of an adult endoparasitic worm, Hirudinella ventricosa, attached to the folds inside the stomach of its primary host, which is a large fish. Image 6 Hirudinella’s thick body wall has a cuticle covered in mucus. The anterior end has two suckers. It feeds on the host’s blood through mouthparts that penetrate the stomach lining. The parasite is hermaphrodite (has male and female reproductive organs). One adult can release many eggs into the host’s digestive tract from which they are egested in faeces. Eggs hatch into larvae which swim in sea water then penetrate the secondary host, a marine snail. Several larval stages reproduce asexually inside the snail. Using the above information together with your knowledge of parasitic nutrition, state what is meant by the term ‘endoparasite’ and distinguish between the terms ‘primary host’ and ‘secondary host’. Suggest how the features of this parasitic life cycle increase the chance of Hirudinella infecting its primary host. Describe the problems encountered by an adult Hirudinella in the stomach of its host and explain how it is adapted to survive in such conditions. [9 QER] 30 mm 30 mm Examiner only (B400U20-1) Turn over. 31 © WJEC CBAC Ltd. 31 Examiner only 32 (B400U20-1) © WJEC CBAC Ltd. 32 Examiner only (B400U20-1) Turn over. 33 © WJEC CBAC Ltd. 33 Examiner only END OF PAPER 9 Examiner only Question number Additional page, if required. Write the question number(s) in the left-hand margin. (B400U20-1) 34 © WJEC CBAC Ltd. 34 (B400U20-1) 35 © WJEC CBAC Ltd. 35 Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only (B400U20-1) 36 © WJEC CBAC Ltd. 36 BLANK PAGE PLEASE DO NOT WRITE ON THIS PAGE