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GCE MAY 2007 : (A2 2) Reproduction, Genetics and Taxonomic Diver

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2007 Biology assessing Module 5: Reproduction, Genetics and Taxonomic Diversity A2B21 Assessment Unit A2 2 [A2B21] TUESDAY 22 MAY, AFTERNOON TIME 1 hour 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Write your answers in the spaces provided in this question paper. Answer all eight questions. For Examiner s use only Question Number INFORMATION FOR CANDIDATES The total mark for this paper is 75. Section A carries 60 marks. Section B carries 15 marks. You should spend approximately 20 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. 1 2 3 4 5 6 7 8 Total Marks A2B2S7 2826 Marks Section A Examiner Only Marks 1 Remark The table below shows the number of chromosomes in the nuclei of the cells of some different organisms. Organism Number of chromosomes Cow 60 Cucumber 14 Garlic 32 Maidenhair fern gametophyte 30 Bramley apple 51 (a) Determine the number of chromosomes that there would be in an ovum from a cow _________________ a pollen tube nucleus from a cucumber _________________ an endosperm cell from garlic _________________ a spore of the Maidenhair fern _________________ [4] (b) The Bramley apple is a polyploid. Using the information in the table, identify the evidence for this and explain why the Bramley apple would be sterile. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] A2B2S7 2826 2 [Turn over 2 The diagram below represents a transverse section through the hypha of a fungus or mould as seen using an electron microscope. Examiner Only Marks Remark cell wall glycogen granule (a) Give two pieces of evidence present in the diagram to suggest that the members of the kingdom Fungi are eukaryotic organisms. 1. _______________________________________________________ 2. _____________________________________________________ [2] (b) With reference to the diagram of the fungus above, describe the sequence of events from the production of enzymes to their use in digestion. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (c) Suggest a role for the glycogen granule labelled on the diagram. _______________________________________________________ [1] (d) Which chemical comprises the cell wall in a fungus? _______________________________________________________ [1] A2B2S7 2826 3 [Turn over 3 The diagram below shows stages in the life cycle of Funaria, a moss plant. Examiner Only Marks reproductive structures Remark reproductive structures capsule fertilisation spirally arranged leaves plant of Funaria moss zygote develops into sporophyte (diploid) growing on gametophyte rhizoids anchor moss plant section spore dispersal simple plant cells of stem and leaf spores germinate to form moss plants (a) Using the information in the diagram, describe the events leading to fertilisation in Funaria. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] A2B2S7 2826 4 [Turn over (b) The diagram includes a section through the moss stem . Identify one difference between this and a section through the stem of a flowering plant. Examiner Only Marks Remark _________________________________________________________ _______________________________________________________ [1] (c) A moss capsule is shown in the diagram. What is the equivalent structure in the fern life cycle? _______________________________________________________ [1] (d) State one similarity and one difference between the moss and the fern life cycles. Similarity _____________________________________________ _____________________________________________________ Difference_____________________________________________ ___________________________________________________ [2] A2B2S7 2826 5 [Turn over 4 (a) Distinguish between the following genetic terms. Examiner Only Marks Remark (i) Gene and allele. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Dominance and epistasis. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (b) In squash plants, fruit colour is determined by the interaction of two genes, W/w and G/g. The W allele suppresses the action of the G/g gene so that white fruit colour is produced. When the genotype is ww, the G/g gene is expressed, with the dominant G allele determining yellow fruit colour while the g allele is expressed recessively as green. Two squash plants of the following genotypes were crossed. WwGg WwGg Determine the expected proportions of the offspring produced with respect to both genotypes and phenotypes. Show your working in a genetic diagram in the following space. A2B2S7 2826 6 [Turn over Examiner Only Marks Remark [4] A2B2S7 2826 7 [Turn over 5 (a) The graphs below illustrate the effect of two different forms of selection (A and B) on the frequency of a characteristic within a population. In each case, the upper graph represents the starting frequencies of the characteristic, with the lower graph illustrating the outcome of the selection process. Frequency B Frequency Frequency Frequency A Characteristic Characteristic Examiner Only Marks Remark (i) Which of the two selection types, A or B, represents stabilising selection? Give a reason for your choice. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Which of the two selection types, A or B, could result in a possible evolutionary change in the population? What is this type of selection known as? _____________________________________________________ ___________________________________________________ [2] A2B2S7 2826 8 [Turn over (b) Describe the process of allopatric speciation. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] A2B2S7 2826 9 [Turn over 6 Tay Sachs disease is a rare genetic disorder of the central nervous system in humans. It is caused by the absence of the enzyme hexosaminidase A (Hex-A). Without Hex-A, a lipid called GM2 ganglioside accumulates abnormally in cells, especially in the nerve cells of the brain. The ongoing accumulation causes progressive damage to the nerve cells and death occurs in early childhood. Examiner Only Marks Remark (a) Tay Sachs disease is controlled by an allele which is autosomal and recessive so that a carrier (heterozygote) does not suffer the condition. Explain why a carrier would be normal with respect to lipid metabolism. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (b) Tay Sachs disease is found predominantly in Ashkenazi (central and eastern European descent) Jewish families. The diagram below shows a pedigree for the inheritance of the disease in a family. 2 1 normal male normal female 3 4 5 6 affected male affected female 7 8 9 10 (i) Using the information above, give two reasons for concluding that the allele for Tay Sachs disease is recessive. 1.____________________________________________________ _____________________________________________________ 2.____________________________________________________ ___________________________________________________ [2] A2B2S7 2826 10 [Turn over (ii) Explain how you would conclude from the above information that the allele for Tay Sachs disease is not located on the X-chromosome. Examiner Only Marks Remark _____________________________________________________ ___________________________________________________ [1] (c) Within the Ashkenazi Jewish population in America, 4 in 10 000 births exhibit Tay Sachs disease. The population is assumed to be in Hardy Weinberg equilibrium. (i) Calculate the relative frequency of the Tay Sachs allele and the normal allele in the population. (Show your working in the space below.) Relative frequency of the Tay Sachs allele ________________ Relative frequency of the normal allele _________________ [3] (ii) Calculate the number of carriers in a population of 10 000. (Show your working in the space below.) Number of carriers in the population___________________ [1] (iii) Explain why it is not reasonable to assume that the population is in Hardy Weinberg equilibrium with respect to the Tay Sachs allele. _____________________________________________________ ___________________________________________________ [1] (d) A test is available that measures the amount of Hex-A enzyme in the blood. Tay Sachs carriers have about 60% of the enzyme levels of non-carriers (homozygous normal). Explain how genetic counsellors might advise couples about the test results so that they know whether or not children would be at risk of the disease. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] A2B2S7 2826 11 [Turn over 7 The New Zealand flatworm (Arthurdendyus triangulates) is an invasive earthworm predator that is now widespread in Northern Ireland, having first been recorded in 1963 in a garden in Belfast. Its establishment in N. Ireland is probably dependent upon three main factors: the presence of earthworms that make up the bulk of its diet, a soil temperature range that does not exceed certain values and a relatively humid or damp microclimate. It is considered that the flatworm has had an adverse effect on earthworm populations. Examiner Only Marks Remark (a) Flatworms belong to the phylum Platyhelminthes, while earthworms belong to the phylum Annelida. (i) Identify one structural similarity between platyhelminths and annelids. _____________________________________________________ ___________________________________________________ [1] (ii) Identify three structural differences between platyhelminths and annelids. 1.____________________________________________________ _____________________________________________________ 2.____________________________________________________ _____________________________________________________ 3.____________________________________________________ ___________________________________________________ [3] (b) Suggest why flatworms could only inhabit humid or damp environments. _________________________________________________________ _______________________________________________________ [1] (c) A laboratory investigation has been carried out into the effects of exposure to high and low temperatures on the survival of the New Zealand flatworm. The mortality of flatworms exposed to various temperatures in the range 2 C to 23 C, and over a period of approximately 3 weeks, was measured. The resultant mortality curves are shown in the graph opposite. A2B2S7 2826 12 [Turn over 100 Examiner Only Marks Remark 90 2 C 1 C 0 C 8 C 18 C 22 C 23 C 80 Mortality/% 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 Time of exposure/days 16 18 20 22 What conclusions can be made about the effect of temperature on the survival of the New Zealand flatworm? Suggest how this may have affected its spread through Northern Ireland and comment on its ability to colonise other parts of Europe. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] A2B2S7 2826 13 [Turn over (d) Suggest how you would plan an ecological investigation to test the hypothesis that flatworms have had an adverse effect on earthworm populations . Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] A2B2S7 2826 14 [Turn over Examiner Only Marks Remark BLANK PAGE (Questions continue overleaf) A2B2S7 2826 15 [Turn over Section B Examiner Only Marks Remark In this section you are expected to answer in continuous prose, supported, where appropriate, by diagrams. You are reminded that up to two marks in this question are awarded for the quality of written communication. [2] 8 Give an account of micropropagation (plant tissue culture), explaining: (a) the techniques involved, including the selection of the tissues to be propagated, the maintenance of sterile conditions, the nutrients used in the culture medium and the use of plant growth regulators; [7] (b) the advantages and problems associated with producing plants by tissue culture. [6] ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B2S7 2826 16 [Turn 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____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B2S7 2826 18 [Turn over ____________________________________________________________ Examiner Only Marks Remark ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ 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____________________________________________________________ ____________________________________________________________ A2B2S7 2826 21 [Turn over THIS IS THE END OF THE QUESTION PAPER A2B2S7 2826 22 [Turn over Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. S 6/06 7-078-1

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Additional Info : Gce Biology May 2007 Assessment Unit A2 2 - Module 5: Reproduction, Genetics and Taxonomic Diversity
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