0610_w12_qp_32
A paper of Biology, 0610
Questions:
6
Year:
2012
Paper:
3
Variant:
2
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1
For Examiner's Use The fungus, Trichophyton violaceum, reproduces asexually by releasing spores. A single spore was placed in the centre of a Petri dish containing an agar medium with starch and protein. shows the fungus that grew from the spore. State the name given to the body of the fungus that grows from a single spore the thin threads that make up the body of the fungus. Describe how a fungus, such as T. violaceum, obtains nutrients from the agar medium. For Examiner's Use Streptomyces, a soil bacterium, is a major source of antibiotics that are produced by pharmaceutical companies. An antibiotic sensitivity test can be carried out to help doctors decide which antibiotic should be used to treat a specific disease, such as gonorrhoea. Gonorrhoea bacteria isolated from a person are grown on an agar medium. A ring with eight different antibiotics (1 to 8) is placed on the agar medium and left for 24 hours at 35 °C. shows the growth of bacteria on the agar medium after 24 hours. bacterial growth Suggest why there is a clear area around some of the antibiotics. Explain why antibiotics 1 and 5 would not be chosen to treat the gonorrhoea infection. For Examiner's Use People who take antibiotics should always be told to complete the treatment rather than stop taking the antibiotics when they feel better. Suggest why people are given this advice.
15. Drugs  →  15.1. Drugs
21. Biotechnology and genetic modification  →  21.2. Biotechnology
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2
For Examiner's Use The glucose concentration of the blood is maintained within the range 80 – 90 mg per 100 cm3 blood. is a flow chart showing how the body responds to changes in the glucose concentration of the blood after the absorption of a carbohydrate-rich meal and during strenuous exercise. change in blood glucose concentration detected by organ A blood glucose concentration increases above 90 mg per 100 cm3 large carbohydrate-rich meal followed by absorption of glucose from small intestine blood glucose concentration decreases below 80 mg per 100 cm3 organ A releases hormone B into the blood organ A releases hormone C into the blood blood glucose concentration decreases blood glucose concentration increases hormone B stimulates organ D to convert glucose to glycogen hormone C stimulates organ D to convert glycogen to glucose muscle contraction during strenuous exercise blood glucose concentration returns to 80 – 90 mg per 100 cm3 For Examiner's Use Name organ A and hormones B and C. A B C Name organ D that stores glucose as glycogen. Suggest why glucose is converted to glycogen rather than kept as glucose inside the cells. Name the type of control system used in homeostasis that returns the blood glucose concentration to 80 – 90 mg per 100 cm3. Animal hormones are used in the production of milk and meat. Bovine somatotrophin (BST) is used to increase milk production by cows. The hormone is produced by genetically modified bacteria that contain the cattle gene for making BST. It is used in the United States but is banned for use in the European Union. Outline how genes, such as the one for BST, are transferred from the cells of cattle to bacteria. For Examiner's Use Suggest advantages and disadvantages of using hormones, such as BST, in the production of milk and meat. advantages disadvantages
14. Coordination and response  →  14.4. Homeostasis
14. Coordination and response  →  14.3. Hormones
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3
Explain the meaning of the term transpiration. Root hair cells provide a large surface area for the absorption of water from the soil. Explain, using the term water potential, how water is absorbed from the soil into root hair cells. For Examiner's Use Some plants are adapted for life in dry habitats where it can be very hot during the day and very cold at night. shows some saguaro cacti from the Sonoran desert in Arizona and Mexico. shows the surface of the stem of a saguaro cactus. Explain how two features, visible in or , are adaptations to the conditions in the Sonoran desert. feature 1 feature 2 For Examiner's Use The stomata of some desert plants, such as the saguaro cactus, open at night and close during the day. Explain how this allows the cacti to survive in the desert, but limits their growth rate.
8. Transport in plants  →  8.2. Water uptake
8. Transport in plants  →  8.3. Transpiration
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4
For Examiner's Use Enzymes are biological catalysts. Define the term catalyst. Urease is an enzyme found in bacteria and in the seeds of some species of bean. The enzyme catalyses the reaction: urea + water carbon dioxide + ammonia The production of ammonia increases the pH of the area around the bacteria. The formation of ammonia can be used to study the progress of the reaction by testing the pH of the surrounding medium with a pH indicator, such as Universal Indicator solution. Some students carried out an investigation to find out if there was urease in the seeds of four different species of bean. • The germinating seeds were ground up in water and filtered to give an extract containing proteins. • Each extract was added to a urea solution and kept at 30 °C for 30 minutes (tubes 1 to 4). • Two more tubes (5 and 6) were included in the investigation. • Samples were taken from the reaction mixture at five-minute intervals and tested with Universal Indicator solution. The results are shown in Table 4.1. Table 4.1 presence of alkaline pH at intervals of 5 minutes test-tube bean species urea solution water soya yes no        mung yes no        jack yes no        broad yes no        soya no yes        no beans yes yes         = alkaline pH  = not alkaline pH For Examiner's Use Explain why the test-tubes were kept at 30 °C. Explain why test-tubes 5 and 6 were included in the investigation. State the conclusions that the students would make from the results of test-tubes 1 to 4. It is thought that some bean seeds produce ammonia as a protection against infection by microorganisms in the soil. Suggest what would happen to any ammonia that passes into the soil. For Examiner's Use Helicobacter pylori is a bacterium that infects the stomach and causes ulcers. The bacteria secrete urease that helps them to colonise the stomach lining. Explain why bacteria do not usually grow inside the stomach. Suggest how urease helps the bacteria to colonise the stomach. Explain how the immune system protects against infection by bacteria such as H. pylori.
5. Enzymes  →  5.1. Enzymes
4. Biological molecules  →  4.1. Biological molecules
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5
For Examiner's Use shows the changes in carbon emissions from the burning of three fossil fuels between 1800 and 2000. carbon emitted by burning fossil fuels / million tonnes per year year total oil coal natural gas Use the information in to describe the changes in carbon emissions from the burning of fossil fuels between 1800 and 2000. For Examiner's Use All fossil fuels contain hydrocarbons and some also contain compounds of sulfur. Explain how the combustion of these compounds contributes to pollution. hydrocarbons compounds of sulfur Explain the need to conserve fossil fuels, such as coal, oil and natural gas.
19. Organisms and their environment  →  19.3. Nutrient cycles
20. Human influences on ecosystems  →  20.3. Pollution
20. Human influences on ecosystems  →  20.2. Habitat destruction
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6
For Examiner's Use The field mustard plant, Brassica rapa, is cross-pollinated by insects. Describe the advantages of cross-pollination to plants. shows the events that follow pollination in B. rapa. male gamete B ovule A C D E For Examiner's Use Name structures A to E. A B C D E the type of nuclear division that occurs to produce the new cells as the seed grows. Explain why the genotypes of the seeds are not all the same. When ripe, the seed pod breaks open and the seeds are scattered. Some of the seeds germinate and grow into adult plants, but many do not. Explain why many seeds released by B. rapa do not germinate and grow into adult plants.
16. Reproduction  →  16.3. Sexual reproduction in plants
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