6   3 Some lipoproteins may reduce fertility in mammals. (a) An investigation was carried out using mice of the same breed. Female mice were divided into three groups, P, Q and R. Each group was given a different treatment. The table shows the treatment given to the three groups of female mice. Group Treatment P Genetically modified (GM) only Q Genetically modified and supplied with drug K R Supplied with drug K only The GM mice have an increased concentration of high‑density lipoproteins (HDLs) in their blood plasma. Drug K was used to lower the blood plasma HDL levels. The mice in each group were allowed to breed with non‑genetically modified male mice and the number of offspring born was recorded. The graph shows the results. P Q R Group 7 6 5 4 3 2 1 0 Mean number of offspring born per month per female Turn over 7   (i) The mice were all of one breed to improve data (1) A accuracy B precision C quantity D validity (ii) State a null hypothesis for this investigation. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iii) Comment on the effect of blood plasma HDL levels on the fertility of these female mice. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 8   (b) Which of the following are always the same for both mammalian sperm and egg cells of the same species? 1. The total mass of nuclear DNA 2. They both release enzymes by exocytosis (1) A Neither of them B 1 only C 2 only D 1 and 2 (c) The diagram shows a mammalian sperm cell. 1 2 4 3 Which of the labelled parts contains enzymes that phosphorylate glucose during respiration? (1) A 1 B 2 C 3 D 4 (Total for Question 3 = 8 marks) Turn over 9   4 A person arrived at hospital having eaten some poisonous berries. (a) An electrocardiogram (ECG) was recorded for this person. The diagram shows part of the ECG obtained. Z 0.2 seconds (i) Tachycardia for an adult is defined as a heart rate above 100 beats per minute. Calculate the percentage increase above 100 beats per minute for the heart rate of this person. (2) Answer ..............................................................% (ii) The length of time labelled Z on the ECG was shorter than for a person with a normal heart rate. Which of the following is shown by label Z on the diagram? (1) A the time that the atria are contracting B the time for the atrioventricular (AV) valves to open C the time that the atrioventricular node (AVN) delays depolarisation D the time that the ventricles are contracting 10   (b) One of the poisons in the berries can bind to acetylcholine receptors on the surface membrane of cells in the SAN. This prevents acetylcholine binding to the receptors if it is in low concentration. This person was treated with a drug that stopped acetylcholinesterase from being released into the synaptic gap. Explain how this drug lowered the heart rate of this person. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (c) The poison also caused the pupils of this person to dilate. Describe the interaction of the muscles in the eye that led to this dilation of the pupils. 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(Total for Question 4 = 9 marks) Turn over 11   5 A spirometer can be used to study aspects of the human respiratory system. (a) The diagram shows a trace produced using a spirometer. 1 3 4 2 Which of the following parts of the spirometer trace could be used to determine the maximum volume of air that can be exhaled? (1) A 1 only B 2 and 3 combined C 3 only D 3 and 4 combined 12   (b) The availability of oxygen in the air is lower at high altitudes because of the lower air pressure. Populations of humans that have lived at high altitude for many generations have adapted to these conditions. One adaptation these people have is a larger thorax than people living at lower altitudes. A student made the following hypothesis: People with this adaptation will have a lower breathing rate as their tidal volume will be greater than those without the adaptation. (i) Devise a valid investigation, using a spirometer, to test this hypothesis. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... Turn over 13   (ii) Another adaptation to living at high altitude is to have more red blood cells circulating in their blood. Explain how a bone marrow stem cell can give rise to red blood cells. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 5 = 9 marks)