9700_s07_qp_4
A paper of Biology, 9700
Questions:
10
Year:
2007
Paper:
4
Variant:
0
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1
The western lowland gorilla, Gorilla gorilla, has become an endangered species although it has no known enemies, except humans. Gorillas are herbivorous, feeding on fruit, shoots, tree bark and leaves. shows a western lowland gorilla. Suggest three reasons why the western lowland gorilla has become an endangered species. 1. 2. 3. Explain how captive breeding programmes in zoos may help in the protection of endangered species, such as the western lowland gorilla. Examiner’s Use State two disadvantages of captive breeding programmes. 1. 2.
18. Classification, biodiversity and conservation  →  18.3. Conservation
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3
Use Three different strains, A, B and C, of a species of bacterium were grown on nutrient agar in a divided petri dish until they formed ‘lawns’ covering the agar. Three discs of filter paper were soaked in a solution of a penicillin antibiotic and one disc placed in contact with each of the bacterial strains for 10 minutes. After 24 hours, zones of clearance, indicating bacterial cell death, were seen in the ‘lawns’ of strains A and B. The appearance of the petri dish 24 hours after addition of antibiotic is shown in . zone of clearance zone of clearance ‘lawn’ of bacteria growing on nutrient agar position where disc of filter paper soaked in antibiotic had been placed strain A strain B strain C The effectiveness of the antibiotic is proportional to the area of the zone of clearance. Measure the diameters of each of the zones of clearance of bacterial strains A and B and record them to the nearest mm in Table 3.1. Using r2, calculate the area in mm2 of the zone of clearance for each strain of bacterium and record them in Table 3.1. Calculate the ratio of the area for strain A to the area for strain B and record the ratio in Table 3.1. Table 3.1 bacterial strain A B diameter of zone of clearance / mm area of the zone of clearance / mm2 area for strain A : area for strain B Examiner’s Use Explain the different effects of the antibiotic on bacterial strains A, B and C. Describe the role of natural selection in the spread of bacterial strains, such as A and B, when an antibiotic is used. The β-lactam antibiotics, such as penicillin, are similar shaped molecules to the substrate of a bacterial enzyme, transpeptidase. Explain the mode of action of β-lactam antibiotics on susceptible bacteria.
10. Infectious diseases  →  10.2. Antibiotics
17. Selection and evolution  →  17.2. Natural and artificial selection
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Use Describe the role of insulin in the regulation of blood glucose concentration. Question 4 continues on page 8 Examiner’s Use shows some of the steps involved in the production of bacteria capable of synthesising human insulin. mRNA for human insulin isolated DNA coding for human insulin produced DNA coding for human insulin cloned DNA coding for human insulin inserted into a plasmid vector plasmid vector inserted into bacterium State the role of each of the following enzymes in the production of bacteria capable of synthesising human insulin, reverse transcriptase DNA polymerase restriction enzymes (restriction endonucleases) DNA ligase.
19. Genetic technology  →  19.1. Principles of genetic technology
19. Genetic technology  →  19.2. Genetic technology applied to medicine
6. Nucleic acids and protein synthesis  →  6.2. Protein synthesis
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Use Rice, Oryza sativa, is a grass that is grown as a cereal crop in many parts of the world. In most rice-growing regimes, the rice fields are flooded with water while the rice is actively growing. shows cultivation of rice. Describe one structural feature of the tissues in the submerged stems and leaves of rice that is an adaptation for growth in water. Explain the importance of the adaptation you have described in . Examiner’s Use An investigation was carried out into the effect of flooding on the growth of the submerged stems of rice plants. Young rice plants were grown in a container in which the level of water was increased in 10 cm steps, over a period of seven days. The mean length of the submerged internodes (lengths of stem between two leaves) and the concentration of ethene in the rice stems was measured each day. As a control, rice plants were grown in identical conditions but the water level was kept constant throughout the seven days. The results are shown in . 0.0 0.5 1.0 1.5 depth of water / cm mean length of internodes / cm mean concentration of ethene / mm3 dm–3 submerged submerged not submerged not submerged time / days time / days time / days Examiner’s Use With reference to , describe the effect of increasing water level on the length of the submerged internodes. Suggest advantages to the rice plants of the effect that you have described in . With reference to , describe the effect of increasing water level on the concentration of ethene in the rice stems. Examiner’s Use Application of gibberellin can also affect the growth of rice plants. In a further investigation, various concentrations of gibberellin were applied to submerged rice stems. The stems were placed, for three days in closed containers, in which the air supply either contained pure air or contained ethene. Ethene is a gas that is secreted by plant tissues and acts as a plant growth regulator. The results are shown in . no ethene with ethene mean increase in length of stems / mm concentration of gibberellin / nmol dm–3 State the meaning of the term plant growth regulator. Using your knowledge of the effects of gibberellin, and the results shown in , suggest an explanation for the results shown in .
12. Energy and respiration  →  12.2. Respiration
4. Cell membranes and transport  →  4.2. Movement into and out of cells
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Use is a photomicrograph of a section through the ovary of a mammal. Name A and B. A B B A Examiner’s Use shows part of the sequence of processes by which female gametes are produced. cells in germinal epithelium oogonia C P Q secondary oocyte With reference to , name the cell at stage C; draw a label line on to a cell at stage C; name the types of cell division that take place at P and Q. P Q Describe one way in which genetic variation between secondary oocytes is achieved during meiosis.
16. Inheritance  →  16.1. Passage of information from parents to offspring
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Use Sometimes a gene has more than two alleles, termed multiple alleles. The ABO blood group system in humans is controlled by a gene with three alleles, IA, IB and Io. Alleles IA and IB are codominant and Io is recessive to both. The blood group AB is the result of codominance. Explain what is meant by codominance. In humans, a gene that codes for the production of a protein, called factor VIII, is located on the X chromosome. The dominant allele for this gene produces factor VIII, but the recessive allele does not produce factor VIII. A person who is unable to make factor VIII has haemophilia in which the blood fails to clot properly. Explain why a man with haemophilia cannot pass haemophilia to his son but may pass haemophilia to his grandson. Examiner’s Use A gene for feather colour in chickens is carried on an autosome. This gene has two alleles, black (CB) and splashed-white (CW). When a male chicken with black feathers is mated with a female chicken with splashed-white feathers, all the offspring have blue feathers. This also occurs when a male chicken with splashed-white feathers is crossed with a female with black feathers. black feathers splashed-white feathers Another gene may cause stripes on feathers (barred feathers). This gene is carried on the X chromosome. The allele for barred feathers (XA) is dominant to the allele for non- barred feathers (Xa). In chickens the male is homogametic and has two X chromosomes while the female is heterogametic and has one X chromosome and one Y chromosome. barred feathers Examiner’s Use A male chicken with black, non-barred feathers was crossed with a female chicken with splashed-white, barred feathers. All the offspring had blue feathers, but the males were barred and the females were non-barred. Using the symbols given above draw a genetic diagram to show this cross. parents’ male, black, female, splashed-white, phenotype non-barred feathers. barred feathers. genotype gametes offspring genotypes phenotypes male, blue, barred feathers. female, blue, non-barred feathers. Explain how a farmer could use a breeding programme to find out the genotype of a male chicken with blue, barred feathers.
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
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Use Explain what is meant by artificial selection. In a plant breeding programme, corn, Zea mays, was bred in an attempt to produce a high yield of protein in the grain. The results of this programme are shown in . mass of protein / g per 100 g of grain generations Examiner’s Use With reference to , calculate the percentage increase in grain protein by the end of the experiment. Show your working. Answer % Suggest why the protein yield does not increase steadily in each generation. Section B starts on page 22
17. Selection and evolution  →  17.2. Natural and artificial selection
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