9700_w07_qp_2
A paper of Biology, 9700
Questions:
6
Year:
2007
Paper:
2
Variant:
0
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1
shows a bacterial cell dividing by binary fission. magnification = x 37 500 Examiner’s Use With reference to , state three structural features of prokaryotic cells that are not shown by eukaryotic cells. Plant cells divide by mitosis, not by binary fission. State three roles of mitosis in plants. Explain why cells that are produced as a result of mitosis are genetically identical.
5. The mitotic cell cycle  →  5.1. Replication and division of nuclei and cells
5. The mitotic cell cycle  →  5.2. Chromosome behaviour in mitosis
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2
Use Scientists have developed a variety of ways to represent the three dimensional structure of proteins. shows one way of representing the structure of the protein, haemoglobin. A Name A and state its role. name role With reference to , explain why a molecule of haemoglobin is said to show both tertiary structure and quaternary structure. Examiner’s Use shows the oxygen haemoglobin dissociation curve when the partial pressure of carbon dioxide is very low. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen With reference to , state the percentage saturation of haemoglobin with oxygen at 4 kPa % 12 kPa % explain how the shape of the curve between 6 kPa and 2 kPa helps in the delivery of oxygen to respiring tissues. Examiner’s Use Sketch on below the dissociation curve that you would expect if the concentration of carbon dioxide is increased. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen
2. Biological molecules  →  2.3. Proteins
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
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3
Use shows an electron micrograph of some xylem vessels in tobacco leaf fragments in a cigarette. magnification = × 395 Describe and explain two features of the xylem vessels, visible in , that are adaptations for the transport of water in a plant. feature explanation feature explanation Explain the mechanisms that cause movement of water in xylem vessels. Examiner’s Use When tobacco leaf fragments in cigarettes are burnt, substances that are hazardous to health are released. Name three of these hazardous substances and for each describe one effect on the body. substance effect substance effect substance effect
7. Transport in plants  →  7.2. Transport mechanisms
7. Transport in plants  →  7.1. Structure of transport tissues
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4
Use shows the changes in blood pressure in the left atrium, left ventricle and aorta during one complete contraction of the heart. It also shows a recording of the electrical activity of the heart. -3 0.1 0.2 0.3 0.4 0.5 0.6 time / s left atrium left ventricle aorta Key: 0.7 0.8 -2 blood pressure /kPa electrical activity /mV Name the source of the electrical activity in the heart. Examiner’s Use Explain how the heart is coordinated so that the ventricle contracts after the atrium has contracted. With reference to , calculate the heart rate in beats per minute. Show your working and express your answer to the nearest whole number. Answer = beats min–1 The pressure in the right ventricle is rarely higher than 4.0 kPa. Explain why the pressure in the right ventricle is much lower than that in the left ventricle.
8. Transport in mammals  →  8.3. The heart
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5
Use Name the organism that causes tuberculosis (TB). Explain how TB is transmitted from an infected person to an uninfected person. The World Health Organisation (WHO) collects data on TB from its six different regions as shown in Table 5.1. In 2003, it used these figures to estimate • the total number of people with the disease in each region • the number of deaths from TB. Many of those who died from TB were also infected with HIV. Table 5.1 WHO region number of cases per 100 000 population number of deaths from TB (including TB deaths in people infected with Hper 100 000 population Africa The Americas Eastern Mediterranean Europe South-East Asia Western Pacific Explain the advantage of expressing the number of cases and the number of deaths as ‘per 100 000 population’. Examiner’s Use Using the information in Table 5.1, outline the reasons why TB has a greater impact on the health of people in some regions rather than others. The number of cases of TB decreased considerably in many countries during the 20th century. Over the past 20 years, the number of cases worldwide has increased very steeply. A vaccine against TB has existed since 1921. Explain why TB has not been eradicated even though a vaccine has existed since 1921.
10. Infectious diseases  →  10.1. Infectious diseases
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6
Use An ecosystem may be as small as a pond or as large as a forest. Some scientists consider that the whole biosphere is an ecosystem. Give a detailed definition of the term ecosystem. You may use another example in your answer. In 1978, the American ecologist Paul Colinvaux published a book of essays with the title ‘Why Big Fierce Animals are Rare’. Explain why ‘big, fierce animals’ are rare in ecosystems. Many tropical islands have nitrogen-deficient soils. Leguminous trees, such as Royal Poinciana, Delonix regia, grow well in such conditions. Explain why leguminous plants grow well in these conditions.
18. Classification, biodiversity and conservation  →  18.2. Biodiversity
18. Classification, biodiversity and conservation  →  18.3. Conservation
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