2017 HCI H2 Biology Prelims Paper 2 Questions

© Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 16S ___ CENTRE NUMBER INDEX NUMBER BIOLOGY Paper 2 Structured Questions No additional materials are required. 9744/02 23 August 2017 2 hours INSTRUCTIONS TO CANDIDATES There are six question booklets (I to VI) to this paper. Write your name, CT group, Centre number and index number in the spaces provided at the top of this cover page and on the lines provided at the top of the cover pages of Booklets II, III, IV, V and VI. This paper contains nine structured questions. Answer all questions in the spaces provided on the question paper. INFORMATION FOR CANDIDATES 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. The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good Englis h and clear presentation in your answers. This document consists of 28 printed pages and 8 blank pages. For Examiners' Use 1 / 12 2 / 11 3 / 9 4 / 10 5 / 14 6 / 12 7 / 10 8 / 13 9 / 9 Total Mark / 100

2 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 BOOKLET I QUESTION 1 The cell theory was developed in the 1830s. At the same time, it was proposed that living things arose spontaneously from non-living materials. This theory of “spontaneous generation” was later disproven, but the cell theory has stood the test of time to become widely accepted in the scientific community today. (a) Outline the cell theory. [2] Fig. 1.1 shows Louis Pasteur’s famous swan neck flask experiment that disproved the spontaneous generation theory and supported the cell theory. Fig. 1.1 (b)(i) With reference to Fig. 1.1, explain how Pasteur’s experiment supports the cell theory. [2] Short time Long time Liquid remains microbe-free indefinitely Microorganisms grow in liquid Microorganisms trapped in bend Flask remains upright Flask tipped so that microorganisms contact sterile liquid Steam forced out open end Liquid sterilised by extensive heating Non-sterile liquid (nutrient broth) poured into flask

3 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 (a)(ii) Suggest a reason for the universal acceptance of the cell theory in our world today. [1] Pseudomonas syringae is a pathogen that can enter plants through wounds and cause disease in a wide variety of plants. Fig. 1.2 is an electronmicrograph of a cell belonging to the same domain as P. syringae. Fig. 1.2 (c)(i) State the name and chemical composition of the structures labelled A to C. A B C [3] (c)(ii) P. syringae colonises a host plant and obtains nutrients from the plant tissue. It can cause damage to the leaves of its host plant by secreting toxins and cell wall degrading enzymes, without causing harm to itself. Explain why this is so. [2] A B C ×100 000

4 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 When two organisms live in close association with each other, the following are three different possible outcomes:  parasitism occurs in the host-pathogen interaction between P. syringae and the host plant because the pathogen benefits while the host is damaged.  mutualism occurs when both host and pathogen benefit.  commensalism occurs when the pathogen benefits but the host neither gains nor loses. Based on the endosymbiotic theory, mitochondria in eukaryotes originated from free-living oxygen- metabolising eubacteria that were engulfed by an ancestral eukaryotic cell , which was otherwise unable to use oxygen. (d) State and explain which of the three types of interactions best describes the relationship between the ancestral eukaryotic cell and its endosymbiont. [2] [Total: 12]

5 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 2 Fig. 2.1 is an electronmicrograph of a lymphocyte in the process of cell division during an immune response. Fig. 2.1 (a) With reference to Fig. 2.1, (i) name the stage of mitosis. [1] (ii) describe what is happening during this stage of mitosis. [2]

6 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 Stem cells from human bone marrow that are involved in blood cell formation are described as multipotent, rather than totipotent. (b) Distinguish between multipotent cells and totipotent cells. [2] Treatment of leukaemia using bone marrow transplants from donors with matching tissue types was first carried out in 1968. Treatment with adult stem cells extracted from the patient’s bone marrow is a much more recent treatment. After removal of the stem cells, the remaining bone marrow cells and white blood cells in the patient, including the cancer cells, are killed. The stem cells are separated from the cancer cells in the extract. The remaining stem cells are returned to the patient’s body. This procedure is still rarely used as it currently gives a greater risk of cancer in the future. Several lines of research involving stem cells have shed some light on the causes of cancer. In some cases, the use of stem cells in treatment appears to increase the risk of cancer. (c) Suggest why there might be a connection between the use of stem cells in treatment and cancer. [3]

7 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 In another line of research, scientists have discovered the formation of cybrids (cytoplasmic hybrid cells). Stem cells may be harvested from cybrids for research or medical purposes. Fig. 2.2 shows the steps in the production of a cybrid. The DNA of such a cybrid is 99.6% human. Fig. 2.2 Ovum taken from a cow. Remove intact nucleus and discard. Insert intact nucleus of human cell to produce a cybrid. The cybrid then transferred to a Petri dish containing culture medium. The cell divides to the blastocyst stage. Under UK regulations the blastocysts may not be allowed to develop beyond 14 days. Cybrids now grow and divide to produce stem cells. Add different chemical substances to cause differentiation into different cell types for research, e.g. into Parkinson’s disease. cytoplasm nucleus nerve cells blood cells heart cells

8 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 (d) When the Human Fertilisation and Embryology Bill was considered by the UK Parliament in 2008, some people argued that it is unethical to allow the production of cybrids. State whether you agree or disagree that this is unethical and explain why you reached this decision. [3] [Total: 11]

9 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 Candidate Name: CT Group: 16S7 ____ BOOKLET II BLANK PAGE

10 © Hwa Chong Institution 2017 9744 H2 Biol