HCI 2023 JC2 9744 H2 Bio Prelim P3 MS (Sharing)

HWA CHONG INSTITUTION / 2022-2023 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 1 HWA CHONG INSTITUTION (COLLEGE SECTION) 2023 JC2 9744 H2 BIOLOGY PRELIMINARY EXAMINATIONS PAPER 3 MARK SCHEME QUESTION 1 (a) During the last ice age an ice sheet separated southern and northern populations of R. tarandus in North America. (i) Indicate on Fig. 1.2 with an “X” a possible location of the ice sheet formed during the last ice age. [1] any location where there is an overlap in range between subspecies BGS and WS (ii) Explain how this ice sheet affected the evolution of R. tarandus to result in the two different subspecies. [3] 1 ref. to geographical isolation 2 ref. to no gene flow between populations 3 ref. to adaptation to environment (b) Assess the relative importance of natural selection and genetic drift in producing the different body sizes of the two subspecies of reindeer. [2] 1 genetic drift is more important 2 ref. to any valid justification (c) Interbreeding has occurred between individuals of the two subspecies which now live in the area previously covered by the ice sheet. Comment on how the hybrid populations compare to the pure subspecies in terms of genetic variation and potential to adapt to climate change. [2] 1 ref. to hybrid populations with more genetic variation 2 ref. to hybrid populations with more potential to adapt to climate change (d) Table 1.1 in page 2 suggests that the subspecies WS is mainly non-migratory whereas subspecies BGS is primarily migratory. Explain how the data shown in Fig. 1.3 supports the above suggestion. [3] 1 ref. to subspecies BGS having low index of seasonal range overlap 2 ref. to subspecies WS having high index of seasonal range overlap 3 ref. to link between index of seasonal range overlap and migratory / non-migratory behaviour (e) Outline how molecular techniques could be used to test the hypothesis that migratory behaviour in reindeer has a genetic basis. [3] 1 ref. to obtaining DNA 2 ref. to testing both subspecies BGS and WS 3 ref. to use relevant molecular techniques e.g. gel electrophoresis / DNA fingerprinting and compare results to see genetic differences

HWA CHONG INSTITUTION / 2022-2023 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 1 (f) Discuss the importance of the trends observed in Fig. 1.4 for long-distance migratory animals. [4] 1 ref. to energy expenditure inversely proportional to duration of activity 2 ref. to correct supporting data from Fig. 1.4 3 ref. to increase in both muscle aerobic capacity and fatty acid transport in long-distance migratory animals 4 ref. to correct supporting data from Fig. 1.4 (g) (i) Calculate the net number of ATP molecules produced from the complete oxidation of one molecule of 16-carbon palmitoyl CoA. Show your answer clearly in the space provided below. [2] 1 ref. to correct working 2 129 (ii) Suggest why fatty acids can only be respired under aerobic conditions. [2] 1 ref. to fatty acids converted to acetyl coA 2 ref. to role of oxygen in aerobic respiration (h) The Hardy-Weinberg principle states that allele frequencies remain constant from generation to generation. Explain two reasons why this would not apply to the gene pools of species in fragments P, Q and R. [2] 1 ref. to small population size 2 ref. to genetic drift (i) List fragments P, Q and R in order of risk of species extinction, from most to least. Explain your answer. [3] 1 most risk – Q P R – least risk (A: P Q R) 2 ref. to ease / difficulty of gene flow with main population 3 ref. to correct supporting info from Fig. 1.6 (j) Assuming edge effects extend 35 m into each habitat patch, calculate the percentage of the fragment influenced by the edge effects for the second largest patch. Show your working clearly and write your answer in the space in Fig. 1.7. [1] 41.2% (k) Describe the trend in the data and suggest how human activities could affect an abiotic factor that would differ in the area affected by edge effects. [2] 1 ref. to correct trend from data 2 ref. to relevant human activities affecting relevant abiotic factor [Total: 30]

HWA CHONG INSTITUTION / 2022-2023 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 2 QUESTION 2 (a) Suggest how glycoproteins H and F enable the entry of nucleoprotein and viral polymerase into the host cell. [2] 1 Ref to H binding to sialic-acid containing receptors 2 Ref to F allowing fusion of viral envelope with endosome / lysosome (b) Rubella virus contains a single positive sense RNA strand as the genetic material. Suggest how the positive sense RNA strand of rubella virus is utilised in making progeny virus. [2] 1 Ref to viral polymerase converting positive sense RNA to eventually more copies of positive sense RNA 2 Ref to positive sense RNA template for translation of viral proteins (c)(i) Describe how activated B lymphocytes pr oducing IgM would start to produce IgG a few weeks after infection. [2] 1 Ref to class switching 2 Ref to heavy chain constant region of IgM being changed to that of IgG (c)(ii) Using information provided throughout the whole of this question, assess the role of these three classes of antibodies in the immune response to the rubella virus. [4] 1 IgM is produced early in response to virus thus have a role in agglutination of viruses 2 IgA produced early in response and secreted in tears or mucus can cause agglutination, opsonization neutralisation 3 IgG persist in the body to provides sustained immunity to virus 4 IgG can cross placenta, + ref to provide immunity to the fetus [Total: 10]

HWA CHONG INSTITUTION / 2022-2023 H2 BIOLOGY / Preliminary Examination Paper 3 / MS 3 QUESTION 3 (a)(i) Name the type of variation shown in Fig. 2.2. [1] continuous (a)(ii) Suggest and explain how genes and the environment contribute to variation in IPD in humans. [3] 1 Ref. to multiple genes 2 Act on the phenotype in an additive manner 3 Ref. to description of the cumulative effect of varying environmental factors acting on different genotypes / AW (b)(i) State the term that is used to describe a gene, such as PAX3 , that controls the expression of other genes and suggest how the PAX3 protein controls the expression of other genes. [3] 1 Regulatory gene 2 Gene codes for transcription factor 3 that binds to DNA / promoter (b)(ii) Suggest how knowledge of the PAX3 gene helps scientists explain how humans and chimpanzees are very different in facial structure, even though they have very similar DNA. [3] 1 Ref. to one gene contributing to big p