2017 RVHS H2 Biology Prelims Paper 3 Answers

River Valley High School Pg 1 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION II CANDIDATE NAME CENTRE NUMBER S CLASS INDEX NUMBER H2 BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 20 Sep 2017 2 hours Additional Materials: Writing Paper READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question on the separate writing paper provided. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is gi ven in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 /19 2 /18 3 / 13 Section B 4 or 5 /25 Total / 75 _____________________________________________________________________ This document consists of 18 printed pages.

River Valley High School Pg 2 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II Section A Answer all the questions in this section. 1 The Galapagos Islands is an archipelago approximately 1400 kilometers off the Western coast of Ecuador. It consists of more than 40 islands, including the small and isolated island Daphne Major. The map of the islands, and its location in relation to mainland Ecuador and Cocos Island, is shown in Fig. 1.1. Fig. 1.1 There are now at least 13 species of finches on the Galapagos Islands, each filling a different niche on different islands. All of t hem evolved from one ancestral species, which colonised the islands only a few million years ago. Molecular analysis was carried out on the nucleotide sequences of the Galapagos Islands finches and the Cocos finch, found on the island of Cocos, 830 km North-east of the Galapagos Islands. Fig. 1.2 shows the phylogeny of these finches as constructed from the molecular data obtained.

River Valley High School Pg 3 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II Fig. 1.2 (a) Explain how DNA sequences can be used to determine evolutionary relatedness between species. [2] 1. Compare homologous DNA sequences/ same gene; 2. found in different species; 3. The fewer the differences in the DNA sequences of homologous genes between species, the more closely related the species are (vice-versa);; (b) Suggest how the Cocos finch might be derived from the same common ancestor as the Galapagos finches, despite its lack of proximity to the Galapagos Islands. [1] 1. Last common ancestor to Galapagos and Cocos finch first dispersed to Cocos from Ecuador, then to the Galapagos islands;; 2. Last common ancestor to both finches was transported to Cocos islands due to human factors (by air/ship) from Ecuador / Galapagos Islands;; 3. Last common ancestor to both finches was dispersed to Cocos island by an extreme weather event;; A long-term study of the medium ground finch, Geospiza fortis , was carried out on the island of Daphne Major. Ground finches have b ills particularly suited to eating seeds. Seeds eaten by the population of G. fortis are of a variety of sizes and are from a range of plants. Fig. 1.3 shows a male G. fortis.

River Valley High School Pg 4 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II Fig. 1.3 In 1977, a severe drought affected the Galapagos Islands. The number of different plant species producing seeds and total seed abundance was greatly reduced for the population of G. fortis. Scientists have postulated that the severity of the drought experienced may have been exacerbated by the rise in atmospheric CO 2 concentrations due to human activities. (c) Explain how the emission of greenhouse gases such as CO 2 may be linked to the onset of drought. [2] 1. Increased concentration of greenhouse gases in atmosphere; 2. traps heat and warms atmospheric temperature / leads to warming due to the greenhouse effect; 3. Increased evaporation as a result of rising global temperatures; 4. Lead to dryer environments / longer summers; The population size of G. fortis on Daphne Major fell by over 85% as a result of the 1977 drought. In years with good rainfall there is an abundance of small, soft seeds that are favoured by G. fortis, especially those individuals with smaller bills. In years of drought, small seeds are scarce. Individuals of G. fortis with small bills are rarely successful in extracting seeds from the large, spiky, tough fruits of Tribulus cistoides (Fig. 1.4), which was the main source of seeds at the time. Fig. 1.4 Table 1.1 shows results for mean mass and mean bill size of mature G. fortis before and

River Valley High School Pg 5 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II after the drought. The individuals measured after the drought were a subset of the first sample, allowing a direct comparison of the changes that occurred. Table 1.1 Date of sampling Sample size Phenotypic feature measured Mass / g Bill length / mm Bill depth / mm Bill width / mm 1976 (May) 642 15.79 10.68 9.42 8.68 1978 (March) 85 16.85 11.07 9.96 9.01 Percentage change +6.71 +3.65 +5.73 +3.80 (d) (i) Complete Table 1.1 to show the percentage change in mass and bill depth from 1976 (May) to 1978 (March). [1] (ii) After the drought, the population of G. fortis had significantly higher mean mass and larger mean bill size than the pre-drought population. Name the type of natural selection that was occurring. [1] Directional selection;; (e) Explain how the changes in bill size that occurred in the population of G. fortis on Daphne Major provide support for Darwin’s explanation of how natural selection operates. [3] 1. Mutation leads to phenotypic variation in population; 2. Individuals have different bill size; 3. Lack of small seeds / larger, tougher seeds exerts selective pressure; 4. Birds with bigger bills can break open seeds; 5. Better able to survive and reproduce; 6. Pass on favourable alleles to offspring; 7. Over time, increased frequency of alleles for big bills in population; Current temperatures in the Galapagos archipelago rarely exceed 30°C, even in the summer months. However, climate scientists have warned that in light of global warming, temperatures in the archipelago may soon increase.

River Valley High School Pg 6 of 20 Year 6 H2 Biology 9744 Paper 3 2017 Preliminary Examination II The Intergovernmental Panel on Climate Chang e has forecasted a rise in global average temperatures of up to 5°C over the next century. (f) With reference to Fig. 1.1, suggest how global warming may affect the survival of the finches in the Galapagos Islands. [2] 1. Finches will migrate polewards / to islands in the South as they seek cooler temperatures;; 2. If temperature increases too much, finches may not be capable of flying out of the archipelago and will perish / go extinct;; 3. Melting of glaciers leads to rising sea levels which will flood islands, reducing availability of habitats;; 4. If sea level rise excessively leading to islands being submerged, finches may not be capable of flying out of the archipelago and will perish / go extinct;; Scientists have also suggested that changes in carbon dioxide concentration in the atmosphere changes the stomatal density of plants. 43 different species of plants from a range of habitats we