9700_w06_qp_2
A paper of Biology, 9700
Questions:
6
Year:
2006
Paper:
2
Variant:
0
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1
is a photograph taken at low tide in a mangrove swamp in Mozambique. The photograph shows a hermit crab surrounded by the pneumatophores (‘breathing roots’) of mangrove trees. The hermit crabs live inside the shells of dead molluscs. Large birds, such as Goliath herons, feed on the hermit crabs. The vertical pneumatophores are an adaptation to the soil in the swampy, coastal environment that contains very little oxygen. They are exposed to the air at low tide. The soil has a very high salt content as the sea often covers the area. Some bacteria are able to grow deep in the rich organic mud where the oxygen concentration is very low. Listed below are eight ecological terms that can be applied to the mangrove swamp and the organisms that live there. Use only the information given above to match each organism with the most appropriate term from the list. You may use each letter once, more than once or not at all. mangrove trees all the organisms in the mangrove swamp bacteria deep in the mud all the hermit crabs in the swamp A primary consumer B population C community D niche E secondary consumer F ecosystem G decomposer H producer Examiner’s Use Explain how the cells in the roots of mangrove trees obtain sufficient oxygen and water in this extreme environment. oxygen water
18. Classification, biodiversity and conservation  →  18.2. Biodiversity
12. Energy and respiration  →  12.2. Respiration
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2
Use shows a transverse section of a root nodule of a legume. is a drawing of a cell from the centre of the nodule made from an electron micrograph. cell from centre of nodule mitochondrion cortex bacteria – each within a membrane Name three structures that are present in cells in the cortex of the root that are not present in bacterial cells. Examiner’s Use Explain the advantages of studying cell structure with an electron microscope rather than with a light microscope. Describe the role of Rhizobium in the root nodule. Cells in the centre of the root nodule have a high concentration of the pigment, leghaemoglobin. This combines with oxygen in much the same way as haemoglobin in mammals. Leghaemoglobin is responsible for maintaining anaerobic conditions around the bacteria in the nodules. Leghaemoglobin is not found in the roots of other plants. The base sequence in the gene that codes for the β polypeptide of mammalian haemoglobin is similar to that for leghaemoglobin. Suggest why this is so.
7. Transport in plants  →  7.1. Structure of transport tissues
1. Cell structure  →  1.2. Cells as the basic units of living organisms
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3
Use shows some cells from the lining of the bronchus from a person who has never smoked. shows cells from the same area in a heavy smoker who suffers from chronic bronchitis. Using label lines and the following letters, label the structures A to C on . A cilia B nuclear membrane (nuclear envelope) C endoplasmic reticulum Explain why the lungs are at an increased risk of infection when the bronchial epithelium is damaged as is shown in . Examiner’s Use Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis and emphysema. A student used the World Health Organisation database to investigate the link between cigarette smoking and deaths from COPD. shows deaths from COPD plotted against the mean annual consumption of cigarettes in 20 countries for the period 1997 to 2002. mean annual consumption of cigarettes deaths from COPD per 100,000 in a year The student concluded that there was no link between cigarette consumption and deaths from COPD. Use the information in to discuss the student’s conclusion.
9. Gas exchange  →  9.1. The gas exchange system
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4
Use shows two stages of mitosis in a cell from a root tip of Allium cepa. D E Describe what happens to the chromosomes during mitosis between the stage shown in D and the stage shown in E. Describe the events that occur within a cell after the stage shown in E to allow the formation of two cells. Examiner’s Use A root was cut into ten transverse sections at different distances from the tip. The sections were stained and viewed under the microscope. The number of cells in mitosis were counted in each section and the results were used to determine the mitotic index. This is calculated as follows: mitotic index = number of cells in mitosis ____________________ total number of cells shows the mitotic index for the ten sections. Using the information in , describe how the mitotic index changes along the length of the root. 0.0 0.00 0.02 0.04 0.06 0.08 mitotic index 0.10 0.12 0.5 1.0 distance from root tip / mm 1.5 2.0 Examiner’s Use Explain how the events in the mitotic cell cycle ensure that all the cells in the root are genetically identical.
5. The mitotic cell cycle  →  5.2. Chromosome behaviour in mitosis
5. The mitotic cell cycle  →  5.1. Replication and division of nuclei and cells
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5
Use Table 5.1 shows blood cell counts for three different people. Table 5.1 number of cells per mm3 of blood healthy person at sea level healthy person acclimatised to high altitude person with a bacterial infection red blood cells 5 400 000 6 100 000 5 300 000 T helper lymphocytes 1 000 1 050 phagocytes 5 400 5 600 8 750 Calculate the percentage increase in the number of red blood cells in the person acclimatised to high altitude compared with the person at sea level. Show your working and express your answer to the nearest whole number. Answer = Explain the advantage of this increase in red blood cells to people who live at high altitude. State the roles of phagocytes and T helper lymphocytes during an immune response to a bacterial infection. phagocytes T helper lymphocytes Examiner’s Use Antibiotics are used to treat people with bacterial infections. Explain the danger of the widespread use of antibiotics to treat disease.
11. Immunity  →  11.1. The immune system
8. Transport in mammals  →  8.1. The circulatory system
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6
Use shows three stages in the cardiac cycle. 0.4 s 0.3 s 0.1 s G H J K F Name the blood vessels labelled F and G. F G Examiner’s Use indicates that one heart beat takes 0.8 second. State the heart rate in beats per minute. Answer = Explain why the walls of the atria have thinner muscle than the walls of the ventricles. Complete the table to show what is happening to the following parts of the left side of the heart at each of the stages, H, J and K as shown in : • left atrium • left ventricle • aortic valve. stage left atrium left ventricle atrioventricular valve aortic valve H contracts to force blood into left ventricle open closed J closed K relaxes and fills with blood from left atrium open
8. Transport in mammals  →  8.3. The heart
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